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How Material Specific Tooling Pays Off

A machinist is faced with many questions while selecting the proper tool for their job. One key decision that must be made is whether a material specific tool is appropriate and necessary for the application that’s going to be performed – whether the benefits of using this type of tool outweigh the higher price tag than that of a tool designed for use in a variety of materials. There are four main categories to consider when deciding whether a material specific tool is your best bet: internal tool geometry, coatings, material removal rates (MRR), and cost.

When to Utilize Material Specific Tooling

Are you a machinist in a shop that deals primarily with one type of material? Or, do you generally change materials frequently throughout the day? Further, how many parts do you make at a time? These are questions you must ask yourself prior to making a tooling decision.

Material Specific Tooling is best utilized where several parts are being machined of the same material. For instance, if your shop is machining 1,000 plastic parts, it would be in your best interest to opt for a tool designed for this material as your tooling would not only last longer but perform better. If machining flexibility is paramount for your shop, if you’re only machining a few parts, or if part finish is not of high importance, a regular end mill may suffice.

Pros and Cons of Material Specific Tooling

There are pros and cons to purchasing a Material Specific Tool.

Pros:

  • Tool geometry designed for the material you’re working in to achieve the best results.
  • Coating optimized for the material you’re cutting.
  • More aggressive speeds and feeds, and boosted MRR as a result.
  • Increased tool life.

Cons:

  • Higher upfront cost, though long term savings are possible if used in proper situations.
  • Less opportunity for flexibility. While most end mills may be suitable for use in many jobs and many machines, Material Specific End Mills are engineered for use in specific materials

Special Benefits of Material Specific Tooling

A Unique Internal Tool Geometry

Many manufacturers supply tooling designed for use in specific material buckets. For instance, Harvey Tool has distinct catalog sections for material specific tooling for Hardened Steels, Exotic Alloys, Medium Alloy Steels, Free Machining Steels, Aluminum Alloys, Plastics, Diamond Tooling for Non-Ferrous Materials, and Composites. The special geometry of tools found in these sections is optimized to allow the tool to perform optimally in its select material group.

For instance, a machinist may be faced with a dilemma while preparing to machine a plastic part. While an end mill found in Harvey Tool’s Miniature End Mill section could certainly machine this material, Harvey Tool’s end mill offering designed to machine plastics feature a high rake, high relief design. This is ideal for plastics because you want to effectively cut and form chips while the strength of the tool is less of a concern. The high rake and high relief creates a sharp cutting edge that would quickly break down in metals. However, in plastics, this effectively shears the material and transfers the heat into the chip to produce a great finish in your part.

material specific tooling

Harvey Performance Company, LLC.

Specific Coatings & Substrates for Optimal Performance

One key benefit of opting for a material specific tool is the ability to utilize the best coating option available for that material. Tool coatings serve many functions, including improved lubricity, increased tool life, and a higher-quality part finish. In addition, coated tools can typically be run around 10% faster than uncoated tools.

While many manufacturers will specially coat a standard end mill at your request, this takes added time and cost. In its Material Specific catalog sections, Harvey Tool offers coated tools stocked and ready to ship. For instance, their Hardened Steels and Exotic Alloys categories utilize AlTiN Nano coating. This is a unique nanocomposite coating that has a max working temperature of 2,100° F and shows improved performance in materials such as Hardened Steels, Titantium Alloys, and Inconel, among others.

Increased Material Removal Rates

Because Material Specific Tooling features optimal tool geometry for a job, running parameters are generally able to be more aggressive. Any machinist knows that Material Removal Rates (MRR), is the metric that’s most closely related to shop efficiency, as the more material removed from a part in a given period of time, the faster parts are made and the higher the shop output.

The following example compares running parameters of end mills from Harvey Tool’s Miniature End Mill and Material Specific End Mill Sections. You can notice that while key geometries between the two tools are identical, and are in use in the same material with the same operation, the chip load (+25%), linear feed rate (+33%), and depth of cut (+43%) are boosted. This allows for more material to be removed in a shorter period of time.

Miniature End Mill

Part Number: 836408

Description: 3 Flute 1/8 inch diameter 3x LOC Square Stub & Standard

Material: 6061 Aluminum

Application: Slotting

Speed: 10,000 RPM

Chip Load: .00124 IPT

Linear Feed: 37.2 IPM

DOC: .04375

material specific tooling

Harvey Performance Company, LLC.

 

Material Specific End Mill

Part Number: 942308

Description: 3 Flute 1/8 inch diameter 3x LOC Square Variable Helix for Aluminum Alloys

Material: 6061 Aluminum

Application: Slotting

Speed: 10,000 RPM

Chip Load: .00165 IPT

Linear Feed: 49.5 IPM

DOC: .0625

material specific tooling

Harvey Performance Company, LLC.

Extensive Cost Savings

The following chart displays a cost analysis breakdown between a tool found in the Miniature End Mill section, item 993893-C3; and a tool found in the Material Specific End Mill section, item 933293-C6. When compared for the machining of 1,000 parts, the overall savings is nearly $2,500.

material specific tooling

Material Specific Tooling Summarized

In conclusion, Material Specific End Mills have many benefits, but are best utilized in certain situations. While the initial cost of these tools are higher, they can work to save your shop time and money in the long run by lasting longer and producing more parts over a given period of time.

Nueva Precision – Featured Customer

When it comes to CNC manufacturing services and product development solutions in the Denver, Colorado area, Eddie Casanueva has quickly made a name for himself with his company, Nueva Precision. Eddie has more than 22 years of manufacturing experience and 19 years of business experience, which he uses to help small businesses and entrepreneurs who are looking for product support and development.

Eddie was able to take time out of his busy schedule to talk with us for this Featured Customer post. We covered topics like Eddie’s incredible training and introduction to manufacturing, his experiences using reduced neck end mills, and his suggestions for must-have equipment in any CNC machine shop.

Thanks for taking the time to talk to us for this Featured Customer post. To get started, tell us a little bit about the history behind Nueva Precision and what sort of products you typically manufacture.

Nueva Precision was first incorporated at the end of 2016. Within three months, I was making chips on my own, largely doing prototype work.

I had recently sold my share in another company I co-founded and used that money to move into a larger home in the Denver area that could accommodate a machine shop business. We were lucky enough to find a home with some acreage and an existing oversized garage which was perfect for a shop. Now that I had the building, I had to do things like get the electrical and HVAC up to spec. It required having the city run a stronger electrical line to the building I would use as my shop, but once that was all figured out, we were ready to make some chips.

Nueva Precision

I started by buying a used Haas mill and a used Haas lathe. People initially reached out to me for work because of my quick delivery times. I was able to turn around parts in just a week or two since the business was new. However, within a month of operating those machines, I was already at max capacity with my current equipment. Unfortunately, my lead times had increased to a more standard 4-6 weeks due to the sheer amount of work I was getting. For the rest of 2017, I stuck with my original equipment and just did the best I could to keep up.

nueva precision

Do you have any future plans to expand your shop and capabilities further?

I do! In early 2018 I brought in a brand new VM3 Haas Mill to keep up with demand, but I was curious about how much more revenue that would create. I expected to see a 20-30% increase in revenue, but having another machine ended up doubling my revenue. Luckily my strong relationships with my customers helped me grow the business even as my lead times increased. With that in mind, I just ordered another Haas VM2 at the end of 2018 and am excited to take full advantage of that.

How has your family reacted to you running a business out of your home?

My family has been extremely supportive throughout the whole process. My wife Leandra in particular helps out a lot. She was a teacher for 19 years, but resigned from that profession to work on Nueva Precision. She has started to help out on the business side of things and has also started to help run machines and make parts. My oldest son Jaden (16) is interested in manufacturing and he has started working and making simple parts for us when he is available. All in all, we have a pretty good thing going here.

Eddie and Leandra Nueva Precision

Eddie and Leandra

Jaden nueva precision

Jaden working on parts

How did you first get involved in CNC machining and advanced manufacturing?

I am essentially self-taught in CNC machining. I got started in engineering and manufacturing as a student at the New Jersey Institute of Technology (NJIT) in the Mechanical Engineering program. It was a state school, so tuition costs weren’t bad but I still needed to support myself. I was going to school during the day and pumping gas at night to pay the bills. In my second year in school I came across an opportunity to work at an on-campus research center for manufacturing systems. It was funded by the state of New Jersey to help promote New Jersey industry. The job didn’t have much to do with my curriculum, but they supported some campus research and worked closely with the college on various projects.

The research center had all the workings of a machine shop. There were CNC mills, lathes, injection molding machines, and more. It just looked awesome. I managed to get hired for a job at minimum wage sweeping the shop floor and helping out where I could.

As a curious student, I would ask a million questions of all the machinists and try to do more and more than the usual student employee. John – a talented toolmaker and experienced machinist – took me under his wing and taught me lots of stuff about machining. I started buying tools and building out my toolbox with him for a while, absorbing everything that I could. Next thing I know, they’re handing me prints and I am making parts. A few months down the road the machinists started teaching me programming on a Mazak controller. This went on for a year or so and I just soaked it all in.

nueva precision

Sounds like great experience! Where did you land your first full-time position in manufacturing?

I actually landed my first full-time job at the same manufacturing research center. The center had a CNC machinist programmer resign at the facility, so there was a job opening posted. I went to the director of the center and said I was interested in the position. I knew I had to work a lot to pay my tuition, and if I worked for the university I could get my tuition paid for while also making some real money. The director recommended me for the position, so I interviewed and landed the job. All of a sudden, I had benefits, vacation, real responsibilities, and full-time pay. I flipped my schedule around so I could go to school during nights and work during the day.

I learned so much about machining in my first job because of the unique situation I was in. Companies like Blaser Swisslube, Kennametal, and GibbsCAM were supplying us with product and support to work on process improvements for large New Jersey corporations like BF Goodrich Aerospace, US Can, etc. It progressed to the point where GibbsCAM was actually sending me to seminars to train me on different industry topics to further my education and improve the reports we were outputting.

nueva precision

I was in an amazing position to get all this training and I learned so much in the next 4-5 years. We had equipment like a Fadal 5-Axis CNC Machine and other high tech machines at my disposal, which were very hard to find at the time (mid-1990s). Nobody outside of the most elite machine shops were working in 5-axis, so I had a head start because of this unique job experience.

I actually never finished my degree and instead dove head first into manufacturing. I started my own business on the side and kept working at the research center until 2001 when I left to focus full-time on my new business, Spidertrax Offroad.

Can you tell us more about your experience with Spidertrax Offroad?

Spidertrax Offroad is a manufacturer of drivetrain parts for off-roading vehicles. I started Spidertrax with a partner whom I met in college. The company actually started making our first parts at the research center I was employed at. I asked my boss if I could start making parts off the clock on my own time, and he agreed to let me use the shop. This would have been around 1998, and by 2001 I was ready to take off on my own. My partner and I built that company up to 20 employees, and we were (and they still are) a well-respected brand in the off-roading community.

The hardest part about operating my own business and watching it grow was losing the ability to get out in the shop and actually do what I love, which is making parts. As the business grew, I had to take on more responsibility as a “business man,” and let go of many of the things I enjoyed doing as a machinist. I was very proud of what we had built, but I really wanted to get back to basics. So, in early 2017 I sold my half of Spidertrax Offroad to my partner and took that money to buy the new house and open Nueva Precision, Inc.

What sort of machines and CAM software do you have in your new shop?

Right now for CNC machines I have a 2018 Haas VM3, a 2018 Hass VM2, a 2012 Haas VF2, and a 2012 Haas TL2. I also have an engine lathe, a Bridgeport knee mill, Kaeser screw compressor, which I absolutely love, and a couple of Jet saws.

For software, I still use GibbsCAM. I have been using GibbsCAM since 1996 and have had countless hours of training and experience using it, so I think I’m a lifer.

haas vf2

Outside of tooling, what are some key components of your machining setup that you would recommend to others?

I started Nueva Precision without any sort of probing system in place, and using an umbrella style tool changer. I found out quickly that my time, especially being alone, is worth a lot. I highly recommend getting a solid probing system as well as a side mount tool changer. I added all of that to my VM3 and the effect was immediately noticeable. It is so much more efficient and faster.

Keeping software up-to-date is also key. It can be expensive, but it speaks for itself in just a few months. Any time I invest in technology, it seems to pay off pretty quick.

5th axis workholding

I also feel strongly about having solid workholding. I have a couple of the 5th Axis self-centering vises which are great, and a handful of Kurt vises, as well. I am also a big fan of the MMM-USA guys and their vise jaws and handles. For my shop, flexibility is key because I never know what can come through the door. I don’t do a lot of production work and spend much more time on prototype work, so flexibility is key. Having good quality workholding that I don’t need to worry about lets me swap parts in and out with ease.

As for tool holding, I ran into an issue last year where I was starting to see a lot of tool pullout and was scrapping too many parts as a result of aggressive roughing. I had to find a better solution, and I came across the REGO-FIX PowRgrip system. It might seem expensive compared to other simpler tool holder, but I think the upfront investment isn’t too bad considering the other options in that space. Again, I invested in technology, and immediately saw better results. I currently use the PowRgrip for finishing passes where I need good runout and heavy roughing where there is the highest risk of tool pullout.

REGO powRgrip

You use a lot of Helical’s Reduced Neck end mills. What are some tips or tricks you have learned by using these tools that you could share with others?

My experience with these tools is really new, but I find myself using more and more of them these days. In the beginning, I was afraid of end mills with a longer length of cut singing like crazy in the machine. I started experimenting with the reduced neck tools from Helical and was blown away by the rigidity. The tool pressure remains consistent throughout the part, so you will get the same great results on the top of the part as on the bottom.

I don’t know how many people are currently using them but it makes so much stuff possible. I have gone as large as ¾” diameter with the 5” reach and have never had an issue. Maintaining the low levels of runout is definitely key with these tools, which again comes back to having solid toolholding. Now that I have the REGO-FIX system, I am getting much better runout and plan to start pushing the reduced neck tools even harder.

helical reduced neck end mill

Most of my reduced neck end mills are the standard style, but the chipbreaker with the reduced neck has been a powerhouse for me as well. No matter what I tried with Helical’s reduced neck tooling, I have had success, so I would recommend the entire line if the situation calls for it. Just be careful with runout and make sure to double check your clearance!

What are some of your key Helical products that you use on a daily basis?

My main workhorse is Helical EDP 29422 – the ½” 45 Degree Chipbreaker for Aluminum. I swear I use that tool every single day across all of my machines. That tool is gold for me; it is night and day compared to standard roughers. It has a long enough flute length to be versatile or aggressive, depending on the situation. It is just a great tool. You will need a good holder for sure to keep it from pulling out when you get aggressive, but again my new software and tool holding helps with that.

helical solutions

Outside of performance, I love getting the smaller chips that the chipbreaker tools create. It is so much easier to clean a machine with small chips than long, stringy ones, which saves me time. I do all my roughing with chipbreakers. If you are making stringy chips while running HEM toolpaths, they can be a major pain to deal with.

My customers love the finish that Helical gives me as well. The wiper flat on the bottom of the H40ALV-3 end mill stands out as one of my favorite features on any of my tools. That tool gets me compliments on the floor finishes of pockets and enclosures all the time. Across the board, tool life and finish has been awesome with my Helical end mills. I currently use the Zplus coating for all my aluminum tools and have no complaints.

part finish

This summer I had the privilege of working on some aerospace parts that will be going up into space!  Most all parts were being machined from pre-hardened stainless steels and exotic alloys.  The Helical 5-flute and 7-flute endmills with the Aplus coating proved to be great tools to have in the arsenal.

What are your “go-to” Harvey Tool products?

For Harvey Tool, I use a lot of the full radius Keyseat Cutters to surface mill areas you can’t get to with a ball nose end mill. This saves me valuable time because I can avoid flipping the part to surface mill both sides by doing it all in one operation with the Keyseat Cutter.

keyseat cutter

Outside of the keyseats, I use a lot of miniature end mills with reduced shanks and chamfers mills in a variety of angles. I also use lollipops (undercutting end mills) to surface mill parts with hard-to-reach holes.

Overall, being able to look through a single catalog and find tons of options for neck diameters and cutter diameters is what sells me on the Harvey Tool product. It is really neat to have all those different tools available to me in one place – it’s a great catalog.


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Experience the Benefits of Staggered Tooth Keyseats

Keyseat Cutters, also known as Woodruff Cutters, Keyway Cutters, and T-Slot Cutters, are commonly used in machine shops. Many machinists opt to use this tool to put a slot on the side of a part in an efficient manner, rather than rotating the workpiece and using a traditional end mill. A Staggered Tooth Keyseat Cutter has alternating right-hand and left hand shear flutes and is right-hand cut, whereas a traditional keyseat cutter has all straight flutes and is right-hand cut. Simply, the unique geometry of a Staggered Tooth Keyseat Cutter gives the tool its own set of advantages including the ability to index within the slot, increase feed rates, and achieve better part finish.

staggered tooth keyseat cutter

Three Key Benefits

Indexing

The alternating right-and-left-hand flutes of a Harvey Tool Staggered Tooth Keyseat Cutters are relieved on both sides of its head, meaning that it allows for both end cutting and back cutting. This adds to the versatility of the staggered tooth keyseat cutter, where one singular tool can be indexed axially within a slot to expand the slot to a specific uncommon dimension. This can save space in a machinist’s magazine and reduce machine time by eliminating the need to swap to a new tool.

Increased Feed Rates

Due to the unique geometry of a Staggered Tooth Keyseat Cutter, chips evacuate efficiently and at a faster rate than that of a Straight Flute Keyseat Cutter. The unique flutes of Staggered Tooth Keyseat Cutters are a combination of right-and-left-hand shear flutes, but both types are right-hand cutting. This results in the tool’s teeth alternating between upcut and downcut. Chip packing and chip recutting is less of a concern with running this tool, and results in increased chip loads compared to that of a standard keyseat with the same number of flutes. Because of this, the tool can account for chiploads of about 10% higher than the norm, resulting in heightened feed rates and shorter cycle times overall.

Better Part Finish

Staggered Tooth Keyseat Cutters have “teeth”, or flutes, that are ground at an angle creating a shear flute geometry. This geometry minimizes chip recutting, chip dragging and reduces the force needed to cut into the material. Chip recutting and dragging are minimized because chips are evacuated out of the top and bottom of the head on the side of the cutter that is not engaged in the material. Shear flutes also reduce vibrations that can lead to chatter and poor finish. By minimizing cutting forces, vibration, and chatter, a machinist can expect a better part finish.

staggered tooth keyseat cutter

Image courtesy of @edc_machining

Staggered Tooth Keyseat Cutter Diverse Product Offering

On top of the higher performance one will experience when using the Stagger Tooth Keyseats, there are also multiple options available with various combinations to suit multiple machining needs. This style is offered in a square and corner radius profile which helps if a fillet or sharp corner is needed. There are also multiple cutter diameters ranging from 1/8” to 5/8”. The increased diameter comes with an increase of radial depth of cut, allowing deeper slots to be achievable. Within the most popular cutter diameters, ¼”, 3/8”, and ½” there are also deep slotting options with even greater radial depth of cuts for increased slot depths. On top of the diameters and radii, there are also multiple cutter widths to choose from to create different slots in one go. Finally, an uncoated and AlTiN coatings are available to further increase tool life and performance depending on the material that is being cut.

Opt for a Smoother Operation

A Staggered Tooth Keyseat Cutter adds versatility to a tool magazine. It can be indexed axially to expand slots to make multiple widths, allowing machinists to progress operations in a more efficient manner where tool changes are not required. Further, this tool will help to reduce harmonics and chatter, as well as minimize recutting. This works to create a smoother operation with less force on the cutter, resulting in a better finish compared to a Standard Keyseat Cutter.

For more information on Harvey Tool Staggered Tooth Keyseat Cutters and its applications, visit Harvey Tool’s Keyseat Cutter page.

Best Practices of Tolerance Stacking

Tolerance stacking, also known as tolerance stack-up, refers to the combination of various part dimension tolerances. After a tolerance is identified on the dimension of a part, it is important to test whether that tolerance would work with the tool’s tolerances: either the upper end or lower end. A part or assembly can be subject to inaccuracies when its tolerances are stacked up incorrectly.

The Importance of Tolerances

Tolerances directly influence the cost and performance of a product. Tighter tolerances make a machined part more difficult to manufacture and therefore often more expensive. With this in mind, it is important to find a balance between manufacturability of the part, its functionality, and its cost.

Tips for Successful Tolerance Stacking

Avoid Using Tolerances that are Unnecessarily Small

As stated above, tighter tolerances lead to a higher manufacturing cost as the part is more difficult to make. This higher cost is often due to the increased amount of scrapped parts that can occur when dimensions are found to be out of tolerance. The cost of high quality tool holders and tooling with tighter tolerances can also be an added expense.

Additionally, unnecessarily small tolerances will lead to longer manufacturing times, as more work goes in to ensure that the part meets strict criteria during machining, and after machining in the inspection process.

Be Careful Not to Over Dimension a Part

When an upper and lower tolerance is labeled on every feature of a part, over-dimensioning can become a problem. For example, a corner radius end mill with a right and left corner radii might have a tolerance of +/- .001”, and the flat between them has a .002” tolerance. In this case, the tolerance window for the cutter diameter would be +/- .004”, but is oftentimes miscalculated during part dimensioning. Further, placing a tolerance on this callout would cause it to be over dimensioned, and thus the reference dimension “REF” must be left to take the tolerance’s place.

stacking tolerances

Figure 1: Shape of slot created by a corner radius end mill

Utilize Statistical Tolerance Analysis:

Statistical analysis looks at the likelihood that all three tolerances would be below or above the dimensioned slot width, based on a standard deviation. This probability is represented by a normal probability density function, which can be seen in figure 2 below. By combining all the probabilities of the different parts and dimensions in a design, we can determine the probability that a part will have a problem, or fail altogether, based on the dimensions and tolerance of the parts. Generally this method of analysis is only used for assemblies with four or more tolerances.

stacking tolerances

                                                               Figure 2: Tolerance Stacking: Normal distribution

Before starting a statistical tolerance analysis, you must calculate or choose a tolerance distribution factor. The standard distribution is 3 . This means that most of the data (or in this case tolerances) will be within 3 standard deviations of the mean. The standard deviations of all the tolerances must be divided by this tolerance distribution factor to normalize them from a distribution of 3  to a distribution of 1 . Once this has been done, the root sum squared can be taken to find the standard deviation of the assembly.

Think of it like a cup of coffee being made with 3 different sized beans. In order to make a delicious cup of joe, you must first grind down all of the beans to the same size so they can be added to the coffee filter. In this case, the beans are the standard deviations, the grinder is the tolerance distribution factor, and the coffee filter is the root sum squared equation. This is necessary because some tolerances may have different distribution factors based on the tightness of the tolerance range.

The statistical analysis method is used if there is a requirement that the slot must be .500” wide with a +/- .003” tolerance, but there is no need for the radii (.125”) and the flat (.250”) to be exact as long as they fit within the slot. In this example, we have 3 bilateral tolerances with their standard deviations already available. Since they are bilateral, the standard deviation from the mean would simply be whatever the + or – tolerance value is. For the outside radii, this would be .001” and for the middle flat region this would be .002”.

For this example, let’s find the standard deviation (σ) of each section using equation 1. In this equation represents the standard deviation.

standard deviation

The standard assumption is that a part tolerance represents a +/- 3  normal distribution. Therefore, the distribution factor will be 3. Using equation 1 on the left section of figure 1, we find that its corrected standard deviation equates to:

tolerance stacking

This is then repeated for the middle and right sections:

standard deviation

After arriving at these standard deviations, we input the results into equation 2 to find the standard deviation of the tolerance zone. Equation 2 is known as the root sum squared equation.

root sum

At this point, it means that 68% of the slots will be within a +/- .0008” tolerance. Multiplying this tolerance by 2 will result in a 95% confidence window, where multiplying it by 3 will result in a 99% confidence window.

68% of the slots will be within +/- .0008”

95% of the slots will be within +/- .0016”

99% of the slots will be within +/- .0024”

These confidence windows are standard for a normal distributed set of data points. A standard normal distribution can be seen in Figure 2 above.

Statistical tolerance analysis should only be used for assemblies with greater than 4 toleranced parts. A lot of factors were unaccounted for in this simple analysis. This example was for 3 bilateral dimensions whose tolerances were representative of their standard deviations from their means. In standard statistical tolerance analysis, other variables come into play such as angles, runout, and parallelism, which require correction factors.

Use Worst Case Analysis:

Worst case analysis is the practice of adding up all the tolerances of a part to find the total part tolerance. When performing this type of analysis, each tolerance is set to its largest or smallest limit in its respective range. This total tolerance can then be compared to the performance limits of the part to make sure the assembly is designed properly. This is typically used for only 1 dimension (Only 1 plane, therefore no angles involved) and for assemblies with a small number of parts.

Worst case analysis can also be used when choosing the appropriate cutting tool for your job, as the tool’s tolerance can be added to the parts tolerance for a worst case scenario. Once this scenario is identified, the machinist or engineer can make the appropriate adjustments to keep the part within the dimensions specified on the print. It should be noted that the worst case scenario rarely ever occurs in actual production. While these analyses can be expensive for manufacturing, it provides peace of mind to machinists by guaranteeing that all assemblies will function properly. Often this method requires tight tolerances because the total stack up at maximum conditions is the primary feature used in design. Tighter tolerances intensify manufacturing costs due to the increased amount of scraping, production time for inspection, and cost of tooling used on these parts.

Example of worst case scenario in context to Figure 1:

Find the lower specification limit.

For the left corner radius

.125” – .001” = .124”

For the flat section

.250” – .002” = .248”

For the right corner radius

.125” – .001” = .124”

Add all of these together to the lower specification limit:

.124” + .248” + .124” = .496”

Find the upper specification limit:

For the left corner radius

.125” + .001” = .126”

For the flat section

.250” + .002” = .252”

For the right corner radius

.125” + .001” = .126”

Add all of these together to the lower specification limit:

.126” + .252” + .126” = .504”

Subtract the two and divide this answer by two to get the worst case tolerance:

(Upper Limit – Lower Limit)/2 = .004”

Therefore the worst case scenario of this slot is .500” +/- .004”.

University of Michigan Formula SAE Racing Team – Featured Customer

Formula SAE is a student design competition that began in 1980. The competition was founded by the SAE (Society of Automotive Engineers) branch at the University of Texas. Each year, hundreds of universities across the world spend months designing and manufacturing their best Formula style car before putting them to the test in competitions.

Alex Marshalek is the Team Captain of the University of Michigan’s Formula SAE team, MRacing. The team was originally founded in 1986, and has been very successful over the years. In the 2017 season, they finished 5th at the Formula SAE Michigan event, and took home a 1st place finish at Formula North. They are hoping to continue riding that momentum into another successful season in 2018.

Mracing

Alex reached out to Harvey Tool and Helical earlier this year, and after some conversation, the decision was made to sponsor their team’s efforts by supplying cutting tools and providing technical support. With competitions on the horizon and a new build coming over the summer, Alex was kind enough to find some time to talk with us about his experiences as a student learning the ropes in engineering, manufacturing, and design, the importance of quality tooling and maintaining a superior part finish for competition, and challenges he has faced during this process.

Hi Alex. Thanks for taking the time to talk with us today. When you were looking into college degree programs, what initially interested you in manufacturing and engineering?

I have always had an interest in Aerospace Engineering, but it was nothing more than a personal interest until I started college. My high school unfortunately did not have any machine shop or manufacturing type classes, so a lot of what I knew, I learned from my dad. My dad worked as a Mechanical Engineer at an axle manufacturing company, and he used to always be doing things around the house and showing me the basics of engineering and design.

When it came time to choose a school, I knew that Michigan had an impressive Aerospace Engineering department, and I liked the feel of the campus and community better than other schools I had toured.

How did you first get involved with the Formula SAE team?

I knew going into school that I wanted to get involved in a design team and advance my learning in that way. We have about a dozen different design teams at Michigan, but the Formula SAE team really stood out to me as a really cool project to get involved in.

I started with the team in Fall of 2016, helping out with the design and manufacturing of the vehicle’s suspension. Now, for the upcoming 2018 season, I am taking over the role of Team Captain. There will be a little bit less hands-on design and manufacturing work for me as it is more of an administrative/outreach role.

michigan racing

How does a typical FSAE season run?

So FSAE seasons are constantly running, and nearly overlapping with each other. For example, we are currently finishing up competitions from the 2018 season, but at the same time we are beginning the design of the vehicle for the 2019 season. Typically, the design work is done over the summer, and finalized in October. After that, the major manufacturing begins and lasts until about March, with spare parts and additions being added as we go. Testing begins in March, where we fine tune the vehicle and optimize the design for performance. Then, the rest of the Spring and early Summer is competition time, and the process starts all over again!

What sort of machines do you have in the shop?

Right now, we have three manual Bridgeport mills, two retro-fit CNC Bridgeport mills, 2 manual lathes, 1 retro-fit CNC lathe, and a Haas VF-2SS and Haas SL-20. For the vast majority of what we are machining, we are using the Haas. We do most of our work in Aluminum, with some parts made out of steel or titanium, and the Haas has been great for everything.

We are also using AutoDesk’s Fusion 360 software for our CAD/CAM, and we love it.

What has been the most difficult part of the build?

Time is really the biggest challenge. We are all full-time students, so time is already hard to find, but we also don’t have an overabundance of machinists so the operators can get overburdened. It all works out in the end and our machinists are great, but time management is truly the biggest challenge.

michigan formula sae

The composite materials we work with are also very challenging to machine. We constructed the vehicle’s monocoque (the structural “skin”, often seen in Formula One cars) out of carbon fiber. While we cut a lot of it on the water jet machine, we needed more precise holes than a water jet could offer, so we went to the Haas for that. We were using HSS drills and only getting 10-12 holes at a time before they wore out. However, we had Don Grandt (Harvey Performance Company Application Engineer) stop in the shop and he sent us a few Harvey Tool diamond coated drills, which should make this a much faster and more precise process!

You mentioned Don stopped in to give you guys a visit. What were some of your biggest takeaways?

Don was great. He stopped by and we gave him a tour of the facility and showed off some of the parts we were designing. We talked shop for quite a bit, and he gave us a bunch of great tips and tricks we could use to really optimize our machining. As I mentioned, he also went through the catalogs with us and helped us find exactly what we need for tooling. The Harvey Tool diamond coated drills are going to be a life saver for carbon fiber. I guess the biggest takeaway was just all of the knowledge we received from Don and how helpful that was to have someone direct from the tooling manufacturer sharing everything we knew with us.

Now that you have the Harvey and Helical tools in the shop, how have they helped you complete this project and get a leg up on your competition?

One of the most impressive things for us have been the finishing end mills we received. The Helical finishers for Aluminum are giving us some of the best finishes we have ever seen. For us, that is a point of pride. We not only want to have the fastest and most well-designed vehicle, but we also want to have the best looking parts. Subpar finishes reflect poorly on the entire build, and first impressions mean a lot in these competitions.

We have also been blown away by the Chipbreaker roughers. We absolutely love those tools and push them to the limits with great results. In fact, the first time we ran them, we used Machining Advisor Pro to dial in our speeds and feeds, and the numbers seemed insane to us. We were nervous, but we pushed the button and let it run. It was amazing to see that we could push a tool that fast without tool failure.

How has your experience been using Machining Advisor Pro?

We use Machining Advisor Pro every time we picked up the Helical end mills. MAP was actually one of the main reasons we were looking for Helical to sponsor us. We had heard a lot about MAP and your level of technical support, which was important to us as we are learning more about manufacturing and machining. Machining Advisor Pro has quickly become one of our best learning tools in the shop.

The nice thing about MAP is that is takes a look at all of the parameters. A lot of applications only give you numbers on your speeds and feeds, but MAP takes a look at the depth of cut, chip thinning, engagement angle, and all of the other parameters that are so essential to a successful run. As a result, we have been able to get very aggressive with the end mills. We are not a huge production shop, so cycle times are not as important, but we still want to get the most out of our tools in the least amount of possible time.

So, let’s break down some specs. What are you all working with on this year’s build?

Right now our car features a 4 cylinder Honda 600 CBR engine, with a Turbo and 600cc displacement. We are one of the few teams that run a turbo in competition. As we mentioned, the monocoque is completely carbon fiber, and the car features a full aero package with an undertray. The max speed is around 80 MPH, and the car weighs 420 pounds without the driver.

Once the build is complete, how does a typical competition work?

Most of the Formula SAE competitions are multi-day events, with a few static events, and then dynamic events where the car is running. For static events, we first have a Design portion. We validate and argue for our design in front of judges who are engineers in the industry. Then, we get into a Cost presentation, as one of the goals is to build the cheapest possible car with a high level of performance. That balance of cost vs. performance is a critical part of the build. The last static event is a Business presentation, where we introduce a business/manufacturing plan on how to get this design to a production level of 100 units in a year.

For the dynamic events, we have 4 different tests. First, we have the Accel Run, which is a 75 meter sprint, and the fastest cars win. From there we go to the Skip Pad event, which is centered on turning radius and the stiffness of the chassis as we do tight figure eight turns with the car.

University of Michigan FSAE

Then we have the AutoCross, a one lap race, which determines our placement in the final event; Endurance. For the Endurance event, we drive the cars around a 22km track, and the goal is to finish the race without any mechanical or design failures in the quickest time possible. Only around 50% of participants actually complete this event. If a single part falls off, or breaks, you are disqualified. Many times we see things like the suspension, powertrain, or wings falling off. It is disappointing when it happens, but it allows us to easily identify any flaws and fix them for the next event.

What is next for you after school? Any future plans or goals?

I am currently majoring in Aerospace Engineering, and would like to stay within that industry. I am leaning towards working on aircraft. Designing either aircraft structures or the aerodynamics would be very cool. I really like the size and scale of working on commercial aircraft, but I could see myself doing something more specialty like working in Defense as well.


Alex and his team had a very successful 2018 season. They recently placed 9th overall in a competition at the Michigan International Speedway. In the dynamic events, they placed 4th in Skidpad, and 7th in Autocross. The high placement in the Autocross event allowed them to race head to head against top teams in the world, and they ended up placing 4th in Endurance out of 104 cars!

The MRacing team also competed at Formula North, a competition in Ontario, Canada, where they achieved a top ranking of 2nd place overall. They passed all of the technical inspections on the first try and placed 1st in Acceleration, 2nd in Skidpad and Endurance, 3rd in Autocross, and 4th in Efficiency.

michigan fsae

Slaying Stainless Steel: Machining Guide

Stainless steel can be as common as Aluminum in many shops, especially when manufacturing parts for the aerospace and automotive industries. It is a fairly versatile material with many different alloys and grades which can accommodate a wide variety of applications. However, it is also one of the most difficult to machine. Stainless steels are notorious end mill assassins, so dialing in your speeds and feeds and selecting the proper tool is essential for machining success.

Material Properties

Stainless steels are high-alloy steels with superior corrosion resistance to carbon and low-alloy steels. This is largely due to their high chromium content, with most grades of stainless steel alloys containing at least 10% of the element.

Stainless steel can be broken out into one of five categories: Austenitic, Ferritic, Martensitic, Precipitation Hardened (PH), and Duplex. In each category, there is one basic, general purpose alloy. From there, small changes in composition are made to the base in order to create specific properties for various applications.

For reference, here are the properties of each of these groupings, as well as a few examples of the popular grades and their common uses.

Category Properties Popular Grades Common Uses
Austenitic Non-magnetic, outstanding corrosion and heat resistance. 304, 316 Food processing equipment, gutters, bolts, nuts, and other fasteners.
Ferritic Magnetic, lower corrosion and heat resistance than Austenitic. 430, 446 Automotive parts and kitchen appliances.
Martensitic Magnetic, moderate corrosion resistance – not for severe corrosion. 416, 420, 440 Knives, firearms, surgical instruments, and hand tools.
Precipitation Hardened (PH) Strongest grade, heat treatable, severe corrosion resistance. 17-4 PH, 15-5 PH Aerospace components.
Duplex Stronger mixture of both Austenitic and Ferritic. 244, 2304, 2507 Water treatment plants, pressure vessels.

Tool Selection

Choosing the correct tooling for your application is crucial when machining stainless steel. Roughing, finishing, slotting, and high efficiency milling toolpaths can all be optimized for stainless steel by choosing the correct style of end mill.

Traditional Roughing

For traditional roughing, a 4 or 5 flute end mill is recommended. 5 flute end mills will allow for higher feed rates than their 4 flute counterparts, but either style would work well for roughing applications. Below is an excellent example of traditional roughing in 17-4 Stainless Steel.

 

 

Slotting

For slotting in stainless steel, chip evacuation is going to be key. For this reason, 4 flute tools are the best choice because the lower flute count allows for more efficient chip evacuation. Tools with chipbreaker geometry also make for effective slotting in stainless steel, as the smaller chips are easier to evacuate from the cut.

stainless steel machining

Finishing

When finishing stainless steel parts, a high flute count and/or high helix is required for the best results. Finishing end mills for stainless steel will have a helix angle over 40 degrees, and a flute count of 5 or more. For more aggressive finishing toolpaths, flute count can range from 7 flutes to as high as 14. Below is a great example of a finishing run in 17-4 Stainless Steel.

 

High Efficiency Milling

High Efficiency Milling can be a very effective machining technique in stainless steels if the correct tools are selected. Chipbreaker roughers would make an excellent choice, in either 5 or 7 flute styles, while standard 5-7 flute, variable pitch end mills can also perform well in HEM toolpaths.

stainless steel

HEV-5

Helical Solutions offers the HEV-5 end mill, which is an extremely versatile tool for a variety of applications. The HEV-5 excels in finishing and HEM toolpaths, and also performs well above average in slotting and traditional roughing. Available in square, corner radius, and long reach styles, this well-rounded tool is an excellent choice to kickstart your tool crib and optimize it for stainless steel machining.

stainless steel machining

Running Parameters

While tool selection is a critical step to more effective machining, dialing in the proper running parameters is equally important. There are many factors that go into determining the running parameters for stainless steel machining, but there are some general guidelines to follow as a starting point.

Generally speaking, when machining stainless steels a SFM of between 100-350 is recommended, with a chip load ranging between .0005” for a 1/8” end mill up to .006” for a 1” end mill. A full breakdown of these general guidelines is available here.

Machining Advisor Pro

Machining Advisor Pro is a cutting edge resource designed to precisely calculate running parameters for high performance Helical Solutions end mills in materials like stainless steel, aluminum, and much more. Simply input your tool, your exact material grade, and machine setup and Machining Advisor Pro will generate fully customizable running parameters. This free resource allows you to push your tools harder, faster, and smarter to truly dominate the competition.

In Conclusion

Stainless steel machining doesn’t have to be hard. By identifying the proper material grade for each part, selecting the perfect cutting tool, and optimizing running parameters, stainless steel machining headaches can be a thing of the past.

4 Essential Corner Rounding End Mill Decisions

A Corner Rounding End Mill is typically used to add a specific radius to a workpiece, or in a finishing operation to remove a sharp edge or burr. Prior to selecting your Corner Rounding End Mill, mull the following considerations over. Choosing the right tool will result in a strong tool with a long usable life, and the desired dimensional qualities on your part. Choosing wrong could result in part inaccuracies and a subpar experience.

Selecting the Right Pilot Diameter

The pilot diameter (D1 in the image above) determines the tool’s limitations. When pilot diameters are larger, the tool is able to be run at lower speeds. But with smaller pilot diameters, the tool can be run faster because of its larger effective cutter radius. The effective cutter diameter is determined by the following equations depending on the radius to pilot ratio:

For a Radius/Pilot Ratio < 2.5, Effective Cutter Diameter = Pilot Diameter + Radius
For a Radius/Pilot Ratio ≥ 2.5, Effective Cutter Diameter = Pilot Diameter + .7x Radius

Larger pilot diameters also have more strength than smaller pilot diameters due to the added material behind the radius. A smaller pilot may be necessary for clearance when working in narrow slots or holes. Smaller pilots also allow for tighter turns when machining an inside corner.

Flared or Unflared

Putting a full radius on a part has the potential to leave a step or an over-cut on a workpiece. This can happen if the tool isn’t completely dialed in or if there is minor runout or vibration. A slight 5° flare on the pilot and shoulder blends the radius smoothly on the workpiece and avoids leaving an over-cut.

A flared Corner Rounding End Mill leaves an incomplete radius but allows for more forgiveness. Additionally, this tool leaves a clean surface finish and does not require a second finishing operation to clean leftover marks. An unflared corner radius leaves a complete radius on the workpiece, but requires more set-up time to make sure there is no step.

Front or Back

Choosing between a Corner Rounding End Mill and a Back Corner Rounding End Mill boils down to the location on the part you’re machining. A Back Corner Rounding End Mill should be utilized to put a radius on an area of the part facing the opposite direction as the spindle. While the material could be rotated, and a front Corner Rounding End Mill used, this adds to unnecessary time spent and increased cycle times. When using a Back Corner Rounding End Mill, ensure that you have proper clearance for the head diameter, and that the right reach length is used. If there is not enough clearance, the workpiece will need to be adjusted.

Flute Count

Corner Rounding End Mills are often offered in 2, 3, and 4 flute styles.  2 flute Corner Rounding End Mills are normally used for aluminum and non-ferrous materials, although 3 flutes is quickly becoming a more popular choice for these materials, as they are softer than steels so a larger chip can be taken without an impact on tool life. 4 flutes should be chosen when machining steels to extend tool life by spreading out the wear over multiple teeth. 4 flute Corner Rounding End Mills can also be run at higher feeds compared to 2 or 3 flute tools.

Corner Rounding End Mill Selection Summarized

The best corner rounding end mill varies from job-to-job. Generally speaking, opting for a tool with the largest pilot diameter possible is your best bet, as it has the most strength and requires less power due to its larger effective cutter diameter. A flared Corner Rounding End Mill is preferred for blending purposes if the workpiece is allowed to have an incomplete radius as this allows more forgiveness and can save on set up time. If not, however, an unflared Corner Rounding End Mill should be utilized. As is often the case, choosing between number of flutes boils down to user preference, largely. Softer materials usually require fewer flutes. As material gets harder, the number of flutes on your tool should increase.

Ideal Tooling for Machining Composites

Composite Materials

A material is classified as a composite if it is made up of at least two unique constituents that when combined yield beneficial physical and mechanical properties for a number of different applications. A binding agent that is the matrix material is filled with either particles or fibers of a second material that act as reinforcements. The combination of strength, weight, and rigidity make composites extremely useful for the automotive, aerospace, and power generation industry. Often the matrix material of particulate-reinforced composites is some form of plastic, and the reinforcement material is either glass or carbon particles. These are sometimes called “filled plastics,” and are typically very abrasive materials. Many composites are layered with varying fiber orientations, which increase the strength of the material and are called fiber-reinforced composites.

Common Problems When Machining Composites

  1. Delamination of composite layers
  2. Uncut Fibers
  3. Fiber tear-out
  4. Uneven tool wear
  5. Poor surface finish due to “competing” materials

These problems are all caused by unique conditions created by composite materials, and can be very tricky to correct.  The simple fact of cutting a combination of multiple materials at the same time introduces many factors that make it difficult to strike the right balance of the proper tool for the job and appropriate running parameters.  The following tool styles provide solutions for a wide array of composite concerns.  Composite Drilling Applications can face the same issues, and proper drill choice can help as well.

Straight Flute End Mill

Straight Flute Composite Cutters are designed to prevent delamination of layered materials by applying all cutting forces radially, eliminating axial forces from a typical helical cutting edge. Cutting action is improved with a high positive rake angle for shearing fibers and eccentric relief for improved edge life. Shallow ramping operations can be performed with this tool, but the largest benefits are seen in peripheral milling applications.

straight flute end mill

Compression Cutters

The Compression Cutter consists of an up cut and down cut helix. The top portion of the length of cut has right-hand cutting teeth with a left-hand spiral. The lower portion of the length of cut has right-hand cutting teeth with a right-hand spiral. This creates opposing cutting forces to stabilize the material removal process when cutting layered composites to prevent delamination, fiber pullout, and burs along the surface. Compression of the top and bottom of the workpiece keeps the layered bonded together.

compression cutter end mill

Chipbreaker Cutter

The Chipbreaker Cutter is ideally suited for roughing and profiling composites with a high percentage of fiber fill. The notch-like chipbreakers shear fibers and shorten chips for improved material evacuation. This specialized geometry is great for keeping chips small and avoiding “nesting” of stringy fibrous chips around the cutter.

chipbreaker for composite materials

Diamond Cut End Mill

Diamond Cut Composite Cutters come in two different geometries: End Mill Style and Drill Mill Style. Although the end mill style tool is center cutting, the drill mill style has a 140° point angle, making it more suitable for plunge cutting. This is great for clearing out pockets in the middle of composite sheets.

diamond cut end mill for composites

End Mills for Composites – Diamond Cut – End Mill Style

 

diamond cut drill mill for composites

End Mills for Composites – Diamond Cut – Drill Mill Style

Both the end mill and drill mill style share the same downcut geometry on the outside diameter. This diamond cut tool receives its name from the combination of left-hand and right-hand teeth. The tool is predominantly a downcut style – a geometry that allows for these tools to effectively rough and profile high fiber reinforced or filled composites, breaking up chips and shearing through fibers.

Diamond Cut vs. Chipbreaker Style

The diamond cut tools have a higher flute count, which some may intuitively think would lead to a better finish, but this is not the case as this line of tools contains right-hand and left-hand teeth. There is a trade-off between an increased ability to shear fibers and leaving a poorer finish. The chipbreaker style tool, although not as effective as shearing fibers, is ultimately designed for the same purpose but leaves a better finish as all of the flutes are facing the same direction.

Composite Finisher

The Composite Finisher has optimized geometry for finishing in composite. A slow helix and high flute count for more contact points ultimately renders a smooth finish by minimizing fraying of fiber-reinforced and layered materials.

finishing end mill for composites

Coating or No Coating?

Composite materials, especially those with glass or carbon fiber, can be particularly abrasive and have a tendency to wear down the cutting edge of carbide tools. If one is looking to achieve the best tool life and maintain a sharp cutting edge, then choosing an Amorphous Diamond coated tool is the best option. This thin coating improves lubricity and wear resistance over its uncoated counterpart. Using a tool with CVD diamond coating can be very beneficial in extreme cases, when fiber fill percentage is very large. This is a true diamond coating, and offers the best abrasion resistance, but a slightly less sharp cutting edge as it is a thicker coating. PCD diamond tooling offers the best tool life. If it a solid diamond wafer brazed to a carbide shank, and can maintain the sharpest edge of any diamond tooling. However, PCD is limited to straight flutes, and can come at a higher price.

Composite materials are being increasingly utilized in today’s manufacturing world for their impressive strength to weight ratio. This growth has stimulated innovative techniques of cutting composites seen in the tool choices above. Harvey Tool’s variety of geometries helps any machine shop tackle composite cutting applications and will continue to offer groundbreaking solutions to these types of manufacturing problems.

Tips for Machining Gummy Materials

Machinists face many problems and challenges when manufacturing gummy materials. These types of materials include low carbon steels, stainless steels, nickel alloys, titanium, copper, and metals with high chromium content. Gummy materials have a tendency to produce long, stringy chips, and are prone to creating built-up edge. These common problems can impact surface finish, tool life, and part tolerances.

Continuous Chip With a Built-Up Edge

Continuous chips are long, ribbon-like chips that are formed when the tool cuts through a material, separating chips along the shear plane created by the tool’s cutting edge. These chips slide up the tool face at a constant flow to create a long and stringy chip. The high temperatures, pressures, and friction produced when cutting are all factors that lead to the sticky chips that adhere to the cutting edge. When this built up edge becomes large enough, it can break off leaving behind some excess material on the workpiece, or gouge the workpiece leaving a poor surface finish.

Coolant

Using large amounts of coolant can help with temperature control and chip evacuation while machining gummy materials. Temperature is a big driving force behind built-up edge. The higher the temperature gets, the easier and faster a built-up edge can form. Coolant will keep local temperatures lower and can prevent the material from work hardening and galling. Long, stringy chips have the potential to “nest” around the tool and cause tool failure. Coolant will help break these chips into smaller pieces and move them away from the cutting action by flash cooling them, resulting in fracturing of the chip into smaller pieces. Coolant should be applied directly to the contact area of the tool and workpiece to have the maximum effect.

Tool Engagement

Running Parameters

The tool should be constantly fed into the workpiece. Allowing the tool to dwell can cause work hardening and increase the chance of galling and built up edge. A combination of higher feed rates and lower speeds should also be used to keep material removal rates at a reasonable level. An increase in feed rates will raise the temperature less than an increase in speed. This relates to chip thinning and the ability of a tool to cut the material rather than rub against it.

Climb Milling

Climb milling is the preferred method as it directs more heat into the chip than the tool. Using climb milling, the largest chip cross section is created first, allowing the tool to cut through the material much easier. The heat generated from friction when the tool penetrates the workpiece is transferred to the chip rather than the tool because the thickest part of the chip is able to hold more heat than the thinnest.

climb milling

Initial Workpiece Engagement

Sudden, large changes in force, like when a tool initially engages a workpiece, have a negative impact on tool life. Using an arc-in tool path to initially engage the material allows for increased stability with a gradual increase in cutting forces and heat. A gradual tool entry such as this is always the preferred method over an abrupt straight entry.

Tool Selection

A tool with a sharp and robust cutting edge should be selected to machine gummy materials. Helical has tooling specifically designed for Titanium and Stainless Steel to make your tool selection process easy.

Additionally, choosing a tool with the correct coating for the material you are machining will help to protect the cutting edge and result in a far lower chance of built up edge or galling than an uncoated tool. A tool with a higher flute count can spread tool wear out over multiple cutting edges, extending tool life. Tool wear is not always linear in gummy materials; as soon as a little bit of wear appears, tool failure will happen relatively quickly. Changing the tool at the first sign of wear may be necessary to ensure that parts are not scrapped.

Gummy Materials Summarized

Every material machines somewhat differently, but understanding what is happening when the tool cuts the workpiece and how this affects tool life and finish will go a long way to successfully completing any job.  Built-up edge and excess heat can be minimized by selecting the correct tool and coating for the material, and following the tips and techniques mentioned above. Finally, be sure to check your machine’s runout and ensure maximum rigidity prior to beginning your machining operation.

Shining a Light on Diamond End Mills

Diamond tooling and diamond-coated end mills are a great option when machining highly abrasive materials, as the coating properties help to significantly increase tool life relative to uncoated carbide tools. Diamond tools and diamond-like coated tools are only recommended for non-ferrous applications, including highly abrasive materials ranging from graphite to green ceramics, as they have a tendency to break down in the presence of extreme heat.

Understanding the Properties of Diamond Coatings

To ensure proper diamond tooling selection, it’s critical to understand the unique properties and makeup of the coatings, as there are often several diamond coating variations to choose from. Harvey Tool, for example, stocks Amorphous Diamond, CVD Diamond, and PCD Diamond End Mills for customers looking to achieve significantly greater tool life when working in non-ferrous applications.

Diamond, the hardest known material on earth, obtains its strength from the structure of carbon molecules. Graphite, a relatively brittle material, can have the same chemical formula as diamond, but is a completely different material; while Graphite has a sp2 bonded hexagonal structure, diamond has a sp3 bonded cubic structure. The cubic structure is harder than the hexagonal structure as more single bonds can be formed to interweave the carbon into a stronger network of molecules.

diamond tool coatings

Amorphous Diamond Coating

Amorphous Diamond is transferred onto carbide tools through a process called physical vapor deposition (PVD). This process spreads a mono-layer of DLC coating about 0.5 – 2.5 microns thick onto any given tool by evaporating a source material and allowing it to condense onto that tool over the course of a few hours.

amorphous diamond coating

Chemical Vapor Deposition (CVD)

Chemical Vapor Deposition (CVD) is a coating process used to grow multiple layers of polycrystalline diamond onto carbide tooling. This procedure takes much longer than the standard PVD coating method. During the coating process, hydrogen molecules are dissociated from the carbon molecules deposited onto the tool, leaving a diamond matrix under the right temperature and pressure conditions. Under the wrong conditions, the tool may be simply coated in graphite. 6% cobalt carbide blanks allow for the best adhesion of diamond and a substrate. CVD diamond coated end mills have a typical thickness of coating that is between 8 and 10 microns thick.

CVD Diamond Coating

Polycrystalline Diamond (PCD)

Polycrystalline Diamond (PCD) is a synthetic diamond, meaning it is grown in a lab and contains mostly cubic structures. Diamond hardness ranges from about 80 GPa up to about 98 GPa. PCD end mills have the same diamond structure as CVD diamond tools but the binding technique is different. The diamond starts in a powdery form that is sintered onto a carbide plate using cobalt as a solvent metal substrate. This is done at an extreme temperature and pressure as the cobalt infiltrates the powder, causing the grains to grow together. This effectively creates a thick diamond wafer, between 010” and .030” in width, with a carbide base. This carbide base is then brazed onto the head an end mill and sharpened.

PCD Diamond CoatingHow Diamond Coatings Differ

Coating Hardness & Thickness

Polycrystalline tools (CVD or sintered) have a much higher hardness, thickness, and max working temperature than Amorphous Diamond oated tools. As mentioned previously, a PCD tool consists of a diamond wafer brazed to a carbide body while a CVD tool is a carbide end mill with a relatively thick layer of polycrystalline diamond grown into it. This grown layer causes the CVD tools to have a rounded cutting edge compared to PCD and Amorphous Diamond coated tools. PCD tools have the thickest diamond layer that is ground to a sharp edge for maximum performance and tool life. The difference between PCD tools and CVD coated tools lies in the thickness of this coat and the sharpness of the cutting edge. Amorphous Diamond tools maintain a sharper edge than CVD coated tools because of their thin coating.

Flute Styles

Harvey Tool’s line of PCD end mills are all straight fluted, CVD coated tools are all helically fluted, and Amorphous Diamond tools are offered in a variety of options. The contrast between straight fluted and helically fluted can be seen in the images below, PCD (top) and CVD (bottom). Electrical discharge machining, grinding or erosion are used cut the PCD wafer to the specifications. The size of this wafer limits the range of diameters that can be achieved during manufacturing. In most situations a helically fluted tool would be preferred over a straight fluted tool but with true diamond tooling that is not the case. The materials that PCD tools and CVD coated tools are typically used to cut produce a powdery chip that does not require the same evacuation that a metallic or plastic chip necessitates.

PCD Diamond end mill

PCD Ball End Mill

CVD Diamond end mill

CVD Ball End Mill

Proper Uses

CVD tools are ideally suited for abrasive material not requiring a sharp cutting edge – typically materials that produce a powdery chip such as composites and graphite. Amorphous Diamond tools have a broad range of non-ferrous applications spanning from carbon fiber to precious metals but ceramics are typically outside their range as they can be too abrasive and wear away the coating. PCD tools overlap their CVD and DLC coated counterparts as they can be used for any non-ferrous abrasive material.

Cut to the Point

Harvey Tool carries physical vapor deposition diamond-like carbon coated tools, chemical vapor deposition diamond tools and polycrystalline diamond tools. PCD tools are composed of the thickest diamond wafer brazed onto a carbide shank and are ground to a sharp edge. CVD coated tools have the diamond grown into a carbide end mill. Amorphous Diamond coated tools have the DLC coated onto them through the PVD process. For more information on the diamond coating best suited for your operation, contact a Harvey Tool Tech Team Member for immediate help.