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Reducing Tool Runout

Tool runout is a given in any machine shop, and can never be 100% avoided. Thus, it is important to establish an acceptable level of runout for any project, and stay within that range to optimize productivity and prolong tool life. Smaller runout levels are always better, but choice of machine and tool holder, stick-out, tool reach, and many other factors all have an influence on the amount of runout in every setup.

Defining Tool Runout

Tool runout is the measurement of how far a cutting tool, holder, or spindle rotates off of its true axis. This can be seen in low quality end mills where the cutting diameter is true to size when measured while stationary, but measures above tolerance while rotating.

The first step to minimizing runout is understanding what individual factors cause runout in every machine setup. Runout is seen in the accuracy of every cutting tool, collet, tool holder, and spindle. Every added connection between a machine and the workpiece it is cutting will introduce a higher level of runout. Each increase can add to the total runout further and further. Steps should be taken with every piece of tooling and equipment to minimize runout for best performance, increased tool life, and quality finished products.

Measuring Runout

Determining the runout of your system is the first step towards finding how to combat it. Runout is measured using an indicator that measures the variation of a tool’s diameter as it rotates. This is done with either a dial/probe indicator or a laser measuring device. While most dial indicators are both portable and easy to use, they are not as accurate as the available laser indicators, and can also make a runout measurement worse by pushing on a tool. This is mostly a concern for miniature and micro-tooling, where lasers should be strictly used due to the tool’s fragile nature.  Most end mill manufacturers recommend using a laser runout indicator in place of a dial indicator wherever possible.

Z-Mike Laser

Z-Mike laser measurement devices are common instruments used to measure levels of tool runout.

Runout should be measured at the point where a tool will be cutting, typically at the end of the tools, or along a portion of the length of cut. A dial indicator may not be plausible in these instances due to the inconsistent shape of a tool’s flutes. Laser measuring devices offer another advantage due to this fact.

High Quality Tools

The amount of runout in each component of a system, as-manufactured, often has a significant impact on the total runout of a given setup. Cutting tools all have a restriction on maximum runout allowed when manufactured, and some can have allowances of .0002” or less. This is often the value that should be strived for in a complete system as well. For miniature tooling down to .001” diameter, this measurement will have to be held to an even smaller value. As the ratio of tool runout to tool diameter becomes larger, threats of tool failure increase. As stated earlier, starting with a tool that has minimal runout is pivotal in keeping the total runout of a system to a minimum. This is runout that cannot be avoided.

Precision Tool Holders

The next step to minimizing runout is ensuring that you are using a high quality, precision tool holder. These often come in the form of shrink-fit, or press-fit tool holders offering accurate and precise tool rotation.  Uniform pressure around the entire circumference of a shank is essential for reducing runout. Set screw based holders should be avoided, as they push the tool off-center with their uneven holding pressure.  Collet-based tool holders also often introduce an extra amount of runout due to their additional components. Each added connection in a tool holding system allows more methods of runout to appear. Shrink-fit and press-fit tool holders are inherently better at minimizing runout due to their fewer components.

tool runout

Included in your tool holding considerations should be machine tool cleanliness. Often, chips can become lodged in the spindle, and cause an obstruction between two high-precision surfaces in the system. Ensuring that your tool holder and spindle are clean and free of chips and debris is paramount when setting up for every job.

Shank Modifications

Apart from equipment itself, many other factors can contribute to an increasing amount of tool runout. These can include how long a tool is, how rigid a machine setup is, and how far a tool is hanging out of its holder.  Shank modifications, along with their methods of tool holding can have a large impact. Often thought of as an older, obsolete technology, Weldon flats are found guilty of adding large amounts of runout in many shops. While many shops still use Weldon flats to ensure a secure grip on their tools, having a set screw pushing a tool to one side can push it off center, yielding very high levels of runout. Haimer Safe Lock™ is another option increasing in popularity that is a much higher performance holding technology. The Safe-Lock™ system is designed with the same tolerances as shrink fit and other high precision tool holders. It is able to minimize runout, while firmly holding a tool in place with no chance of pull-out.

haimer safe lock

The Haimer Safe-Lock™ system is one option to greatly reduce tool runout.

Runout will never be completely eliminated from a machining system. However, steps can (and should) be taken to keep it to a minimum using every method possible. Keeping a tool running true will extend tool life, increase performance, and ultimately save your shop time and money. Runout is a common concern in the metalworking industry, but it is often overlooked when it could be main issue causing part rejections and unacceptable results. Every piece of a machine tool plays a part in the resultant runout, and none should be overlooked.

6 Uses of Double Angle Shank Cutters

A Double Angle Shank Cutter is often referred to as the “Swiss Army Knife of Machining” due to its extreme versatility. This singular tool can be used for chamfering, back chamfering, V-groove milling, deburring, and countersinking. Below, we’ll learn the nuances of each operation, and why a Double Angle Shank Cutter might is an excellent tool to have on hand in any machine shop.


1. Thread Milling

Both in purpose and look, a Double Angle Shank Cutter is very similar to that of a single-form thread mill. Single-form thread mills are more versatile than multi-form thread mills, as they are not locked into a fixed pitch. Double Angle Shank Cutters that have a 60° angle can create internal and external 60° Unified National (UN) and metric threads. Double Angle Shank Cutters with a 55° angle can be used to thread 55° British Standard Pipe Threads (BSPT). To determine the thread sizes that various Double Angle Shank Cutters can produce, it’s helpful to consult thread fit charts, which pair appropriate cutter diameters to the thread size needed.


2. Chamfering

Depending on the requirements of your chamfering operation, and the angle of the chamfer you’re creating on your part, a Double Angle Shank Cutter might be appropriate. The angle of the top or bottom of the cutting face of the tool (called out below in as a B1 dimension), will determine the angle of your part’s chamfer. The area marked in red in Figures 2 and 3 below indicate the cutting portion for your chamfering and back chamfering (leaving a chamfer on the bottom of a part) operation.

For more information on the angles of Double Angle Shank Cutters, view Harvey Tool’s helpful guide: “Angles Untangled.”


3. Back Chamfering

Consider a through-hole that has a burr or tear-out caused from drilling the back of a workpiece. Reorienting the workpiece and relocating the hole is time-consuming, and it may be difficult to accurately finish the hole. In a case like this, back chamfering the burred hole without changing the setup is a preferred method. Put simply, the ability to accurately chamfer not only the top – but also the bottom of a part without needing to refasten the workpiece in your machine will save valuable time and money.

For best results when chamfering with Double Angle Shank Cutters, use a stepping over technique with diminishing passes as the radial engagement increases. This strategy helps to manage the amount of contact along the angle and can significantly avoid tool deflection.


4. Machining V-Grooves

A Double Angle Shank Cutter is commonly applied for machining V-groove profiles because of its cutting head, which is perpendicular to the tool centerline. This provides effective cutting action, even at a low spindle speed. A low tip speed can lead to issues with other tools, such as Chamfer Cutters, where the pointed profile is on-center of the tool.


5. Deburring

The task of hand-deburring parts can be tiresome for you, and cost inefficient for your shop. It can also lead to inaccuracies in parts that require precise dimensions. Double Angle Shank Cutters can be used to debur a part right in your CNC machine. By doing so, the process of finishing a part is made simple, fast, and accurate. Of course, ensuring proper clearance prior to machining the bottom of a machined hole is pivotal.

Other useful and versatile tools to have on-hand for quick CNC deburring include deburring end mills, back deburring mills, undercutting end mills, and chamfer cutters.


6. Countersinking

Countersinking a part  is done so a screw, nail, or bolt is able to sit flush with the part surface. Using specialty profile tooling can help enlarge the rim of a drilled hole and bevel the sides for a screw to sit accurately. A Double Angle Shank Cutter can also perform this operation by using the bottom portion of its cutting face.


Because of its ability to perform six different operations, Double Angle Shank Cutters are an ideal tool to keep in your tool carousel. In a bind, these tool forms can mill threads, chamfer, back chamfer, machine v-grooves, deburr in your CNC machine, and countersink. This versatility makes it a machining favorite and can offer shops boosted productivity by eliminating the need to flip parts, deburr by hand, or carry multiple tool forms.

For more on Harvey Tool Double Angle Shank Cutters, Click Here.

KeyBar – Featured Customer

KeyBar® is a manufacturing company based in Savannah, Georgia that prides itself on American-made products. Mike Taylor, the CEO, Owner, and Founder of KeyBar®, first got the idea for this company while working as the chief engineer at an upscale hotel in Savannah, Georgia. As a part of this position, he carried around countless keys attached to his belt. One day he realized that there must be an easier way to carry his keys, so that they made less noise and were easier to access. Mike used a multi-tool daily, and it occurred to him that he could apply the same concept to keys to create the KeyBar®, a patented key organizer that promises to “Stop the Noise”® of jangling keys, kill the clutter of a handful of keys, and make the key ring obsolete.

In 2014, Mike and his wife, Jessica, left their full-time jobs to take a chance on their new business, and it paid off. Mike, now 34, has built a thriving online store, retailers all over the country are carrying KeyBars, and they have an entire team of employees working at their Savannah, Georgia machine shop; quite the achievement for a young entrepreneur.

KeyBar® also offers other products, including the newly released Quick-Draw, which is a revolver-inspired, rotating desktop pen holder that recently raised over $25,000 in a Kickstarter campaign.

keybar

KeyBars are made of many different materials, ranging from aluminum and copper to brass, titanium, and carbon fiber, and end mills from Harvey Tool and Helical Solutions play a crucial part in the creation of each one.

We spoke with Mike for this Featured Customer profile, and talked about his experiences starting his own shop and the way Harvey Tool and Helical products have impacted his shop’s overall performance.

What made you get into machining?

We actually started manufacturing KeyBars by outsourcing our parts to some of my machinist friends. After watching several YouTube videos, I decided that machining our own parts in-house was something I wanted to achieve. I am new to machining, so every day is a challenge. I am truly learning as I go, but I learn more every single day in the shop and every day is a huge payoff.

Would you recommend a career as a machinist to young people trying to find a career path?

Absolutely! In this day and age of smart phones and computers, young people would be great in CNC machining and manufacturing.

How did you first hear about the Harvey Tool & Helical brands?

I first heard about both Harvey Tool and Helical from your Instagram pages. KeyBar® really took off when I started posting the finished product on Instagram, so I have always been an active user and firm believer in the power of social media.

keybar

What made you decide to go with these brands for your cutting tool needs?

I was told that Harvey made the best tool for cutting carbon fiber, which we do a lot of while manufacturing KeyBars, so it was a no-brainer.

How easy was the purchase process?

With only a quick email or phone call, I usually have my tools within 1-2 days, which is important for us to keep up our production and never lose a single second of time in the shop waiting for a tool.

Did you receive any help from our customer service teams? How was that experience?

It was great. I needed some initial speeds and feeds for all my composites, and in just a few minutes they had me all squared away. Time is money, and the customer service team saved me lots of time when we first started working with composite materials.

Tell us about your favorite product that Harvey Tool or Helical products helped to create.

We are currently producing a run of custom KeyBars with inlays. The Harvey end mills for composite materials allowed us to achieve a perfect fit and made the project a success.

keybar

What is your favorite operation to work on with Helical end mills?

I really like working on 1/4″ roughing passes with a Helical chipbreaker.

What was your first impression of these brands’ tools?

“Damn! That worked pretty good!”

You use a lot of Harvey Tool miniature drills in your work. Why is high quality drill performance important to you?

We drill a lot of holes, and every second counts in production. Most importantly, being able to depend on a tool and get consistent results is worth more than anything else.

How have the Harvey Tool and Helical products impacted your overall performance?

I never have to worry about getting a less than superior finish on our composite products. Harvey Tool products do an excellent job with composite materials– like I said, this is a huge part of our manufacturing process and so it is very important to our performance.

If you were stranded on a desert island with only one Harvey Performance tool, which would it be, and why?

I would choose the Harvey Tool 933316-C6 (1/4″ Corner Radius End Mill for Hardened Steels up to 55 Rc) because you never know what you are going to run in to, and there isn’t much that a 1/4″ end mill can’t do!

keybar

Would you like to be considered for a future “Featured Customer” blog? Click here to submit your information.

Photos courtesy of KeyBar

3 Ways to Help Solve the Machinist Shortage

The manufacturing industry is on the rise, but there is a shortage in the workforce that is limiting the abilities of machine shops to find great talent and fulfill their needs. As manufacturing continues to move back to the US, the shortage will only grow larger. With nearly 70% of the machinist workforce over the age of 45, there has to be an injection of youth in the industry over the next 20 years to keep American manufacturing alive and well. Currently employed machinists are the best source to encourage today’s youth to join the profession, so the community will be an integral part of solving this machinist shortage.

1. Reach Out and Get Involved

The best thing machinists can do to make an immediate impact is to begin reaching out to their local communities, sharing their craft with families and students in the area. If we want to solve the machinist shortage, we have to get students excited about the industry. One great way to get students interested is to hold an open house at your machine shop and open your doors to local schools for visits. Since machining is a very visual craft, students will appreciate seeing finished projects in-person and watching the machines at work. Shops could also open their doors to vocational schools and have a “Career Night,” where students who are interested in the trades can come with their families and learn more about what it is like to be a machinist. It is important to get the families of interested youth involved, as colleges will do the same at their open houses, and it gives the family a better sense of where they may be sending their son or daughter after graduation.

machinist shortage

As great as it is to get students and families inside the machine shop, it is equally important for machinists to branch out and attend career days at local schools, as the trades are often underrepresented at these events. Bringing in a few recent projects and videos or photos of more advanced machining processes will be sure to open a few eyes, and might inspire a student who had never considered machining to do some research on the profession.

2. Join Communities on Social Media

According to a report from the Pew Internet Research Center, 92% of high school students use social media daily – a staggering number that must be taken into consideration when it comes to inspiring the younger generations. One easy way machinists can share their work is by using social media apps like Instagram, Facebook, Twitter, and YouTube. Instagram in particular has a great community of machinists, who are constantly sharing videos, tips and tricks, photos of their finished work, and talking to each other about best practices. Many machinist-related Instagram accounts have thousands of followers, and every machine shop should be jumping on this trend not only for their own marketing efforts, but also to get in front of the younger audience present in that space.

machinist shortage

Machinists love sharing their work with the community on social media, like this example from Reboot Engineering (@rebooteng) on Instagram.

If Instagram is not an option, there are several Facebook groups with tens of thousands of machinists talking about the trade, and quite a few influential machinists on YouTube who have substantial followings and are working to raise awareness about their trade. The machinist community on Twitter is smaller than the others, but it is growing and could be a valuable resource going forward.

3. Share Your Knowledge

New machinists will be more likely to embrace the profession and stick around if they are welcomed with open arms and in-depth, hands-on training from the senior machinists in a shop. This will decrease turnover, and keep younger machinists connected to the trade from the start. A machine shop full of veteran machinists can be an intimidating environment for a new hire, so this is a vital step in solving the machinist shortage.

It is also a great idea to share knowledge and stories with younger relatives. Nieces and nephews, younger cousins, grandchildren, and sons and daughters may find inspiration to follow in the footsteps of someone they look up to, but they’ll never know unless those experiences are shared with them.

If you already know someone who is considering a career as a machinist, share our “How to Become a Machinist” blog post with them, which is a great resource for all machine shops looking to hire young talent. This article could be handed out at open houses, career days, or school visits, and is part of Harvey Performance Company’s ongoing effort to improve the manufacturing industry and help solve the machinist shortage.

You can also share our new infographic, which outlines the current state of the industry, and provides a visual representation of how you can help solve this shortage as a current machinist. Use the hashtag #PlungeIntoMachining and share to your Facebook, Instagram, Twitter, and LinkedIn pages to help us start a movement!

Solving the Machinist Shortage

How to Become a Machinist

Machining is one of the fastest growing occupations in the US, with thousands of open positions listed all across various job boards and websites. Because graduating students are more likely to head to college than join the trades, there is currently a major shortage in the workforce for machinists. As the “Baby Boomer” generation inches closer to retirement, this shortage will only continue to grow. According to American Machinist, nearly 70% of the current machinist workforce is over the age of 45, which means there is a great need for younger workers over the next two decades. The Bureau of Labor Statistics (BLS) is predicting a 10% increase in the machinist workforce with opportunities for 29,000 additional skilled machinists by 2024, so it is certainly an exciting time to start thinking about the available career opportunities in the machining industry.

Getting Started

One of the best things about becoming a machinist is that there is a fairly low barrier to entry level positions. Many machinists start working right out of high school, with 12-18 months of on-the-job training or a 1-2 year apprenticeship. This path generally does not require any experience past a high school education, but prospective machinists are encouraged to take math classes including geometry and trigonometry, and participate in metalworking, drafting, and blueprint reading classes if possible. Chris Metayer, a CNC Operator with Helical Solutions, took this same route to begin his career. “I didn’t know anything about machining when I started, but I trained side by side with other employees. I am a hands-on learner, so it was a perfect learning experience for me.” said Metayer. In the end, most of an entry-level machinists’ learning will be done hands-on in the machine shop while getting paid to learn the craft.

machinist

Others may take a two-year machining-based program at a community college or technical school, where they can learn more advanced skills like Computer Numerical Control (CNC) Machining and Computer Aided Design (CAD) or Computer Aided Manufacturing (CAM) programming.  They would then enter the workforce following the completion of an associate’s degree. These machinists tend to earn higher salaries and are more apt to advance to a management role, but they will also need to pay for the costs of their continued education and will still require some hands-on training before they can jump into their new positions. However, there are added benefits to continuing your education. Jake Barnes, another member of the CNC team at Helical, earned his associates degree in Integrated Manufacturing Technology at Southern Maine Community College, and has worked in various departments since joining Helical. Jake started as a manual grinder, then moved to inspection before landing with the CNC team. “I personally recommend going to a trade school” said Barnes, “You will get exposure to many different classes, which opens up new career opportunities across the industry.”

Some machinists who want to work in more advanced industries like aerospace or tech may attend a four-year college and take advanced courses in calculus, physics, and engineering. All of these options are widely accepted in the machining community, so it is more a matter of personal preference and an individual’s specific situation that determine which path to take.

Location Matters

While there are open jobs for machinists all over the country, there are certainly a few areas that would be considered machinist “hot spots.” These areas of the country have increased job openings in the industry and often pay better wages, since machining skills are in higher demand. The Great Lakes Region (Michigan, Ohio, Illinois, Indiana, Upstate New York, Pennsylvania), and the Southeast (The Carolinas, Louisiana, Georgia, Alabama, Mississippi) are great places to look for work, with over 150,000 currently employed machinists. Most of the work in the Great Lakes Region is dominated by the automotive industry, especially in Michigan. In the Southeast US, there has been a recent influx of manufacturing jobs after plants owned by Apple, Boeing, General Electric, Haier, and LeNovo all opened in the area. In fact, Mississippi offers the highest annual salaries for machinists of any state in the country.

Texas, California, and Washington (especially Seattle) are also hot spots for machining jobs. The west coast holds some of the world’s largest aerospace manufacturing plants, so these areas have plenty of job opportunities for machining and manufacturing.

Salary Expectations

A career as a machinist can be rewarding and fun, especially when it comes to working with different materials and creating amazing and intricate parts. But in the end, compensation matters as well. What is often misunderstood most about this industry is that the salary range for machinists is above the national median.

The Bureau of Labor Statistics (BLS) reported in 2016 that those in the workforce with a high school diploma earned an annual median salary of $36,000, while those with an associate’s degree earned $42,000 across all occupations. The BLS also reported the median salaries for machinists in 2016, with median earnings at $43,200, across all levels of education.

The top 10% of machinists earn over $62,500, and depending on what projects they work on, those wages can go even higher. For example, someone working in the aerospace industry or tech industry can expect to make a higher salary as a machinist, but will likely need to have a more extensive education, which can get costly. Experience also matters, as salaries are likely to increase as machinists get more years under their belts. However, many entry level machinist jobs require little to no educational cost and no experience, so the return on investment can be very high once hired into the industry.

Machinist Career Paths

There are quite a few career paths that a machinist can take once they begin working on their craft. Some machinists will work their way up the shop ladder, going from an entry level CNC operator, to a full-on CNC machinist, and possibly finding themselves in a shop management position at some point in their careers. Others may transition away from machining and begin to work with CAD/CAM or CNC Programming applications, working with the machinists on the floor to program and troubleshoot the machines and design new parts to be created. Many machinists also move into careers in inspection, quality control, or production planning, which can be an excellent way to move up the corporate ladder.

machinist

Working in Inspection is a possible career path for a machinist.

Those who do earn an associate’s degree in a machining-based program should consider a path in engineering. The experiences learned as a machinist translate well to this field, and having an associate’s degree allows for the flexibility of going back to school to finish up a Bachelor’s degree in mechanical engineering. For those who may be unable to go to school full-time, there are many online and part-time courses available. These courses make it possible to work full-time or part-time to advance your skills and attain hands-on experience while earning a degree. Both Barnes and Matayer talked about heading back to school to complete an engineering program at some point, taking advantage of the Harvey Performance Company tuition reimbursement program to advance their education and careers.

The skills learned as a machinist also lay a foundation for becoming an entrepreneur or starting a business. Some machinists will open their own machine shops, manufacturing outsourced parts from other companies, while others will take their skills and create a unique product to fulfill a need they identify in the market.

Do Your Research

As the manufacturing industry continues to grow in America, the shortage of machinists in the workforce will become an incredible source of opportunity for our youth. Breaking into the industry now can set young machinists up for great career opportunities. The skills learned as a machinist also translate well to many different jobs, especially in manufacturing and engineering.

machinist

However, not every machine shop should be treated equal. Potential machinists will want to research shops in their area to find the right fit. As Matayer puts it, “Finding the right shop matters. You want to find a place with newer equipment, great benefits, and clean air in a safe environment.” Poor air quality or unsafe working conditions can directly affect a machinist’s long-term health, so doing the proper research before accepting a position can prevent any serious issues.

If you are curious and want to learn more, reach out to your local trade school or college, talk to a machinist, check out some online forums, and read about the profession. You should also check out the machinist community on Instagram, which is full of amazing customer projects, helpful tips and tricks, and videos that will give you a better idea of what is possible in this field! Machinists are always more than happy to share their experiences, but the biggest thing you can do is try. Get out there, start creating, and see where it takes you – the possibilities are endless!

Multi-Start Thread Reference Guide

A multi-start thread consists of two or more intertwined threads running parallel to one another. Intertwining threads allow the lead distance of a thread to be increased without changing its pitch. A double start thread will have a lead distance double that of a single start thread of the same pitch, a triple start thread will have a lead distance three times longer than a single start thread of the same pitch, and so on.

By maintaining a constant pitch, the depth of the thread, measured from crest to root, will also remain constant. This allows multi-start threads to maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation. A common example is a cap on a plastic water bottle. The cap will screw on in one quick turn but because a multi start thread was used there are multiple threads fully engaged to securely hold the cap in place.

multi-start thread

Figure 1 displays a triple start thread with each thread represented in a different shade. The left side of the image represents a triple start thread with just one of the three threads completed. This unfinished view shows how each individual thread is milled at a specific lead distance before the part is indexed and the remaining threads are milled. The right side of the image displays the completed triple start thread with the front view showing how the start of each thread is evenly spaced. The starting points of a double start thread begin 180° apart and the starting points of a triple start thread begin 120° apart.

multi-start thread

Figure 2 displays the triangle that can be formed using the relationship between the lead distance and the circumference of a thread. It is this relationship that determines the lead angle of a thread. The lead angle is the helix angle of the thread based on the lead distance. A single start thread has a lead distance equal to its pitch and in turn has a relatively small lead angle. Multi-start threads have a longer lead distance and therefore a larger lead angle. The graphic depicted on the right is a view of the lead triangle if it were to be unwound to better visualize this lead angle. The dashed lines represent the lead angle of a single start thread and double start thread of the same pitch and circumference for comparison. The colors represent each of the three intertwined threads of the triple start thread depicted in Figure 1.

Lead Angle Formula

multi-start thread

The charts below display the information for all common UN/Metric threads as well as the lead and lead angle for double and triple start versions of each thread. The lead angle represented in the chart is a function of a thread’s lead and major diameter as seen in the equation above. It is important to be aware of this lead angle when manufacturing a multi-start thread. The cutting tool used to mill the thread must have a relief angle greater than the lead angle of the thread for clearance purposes. All Harvey Tool Single Form Thread Milling Cutters can mill a single, double, and triple start thread without interference.

Machining a Multi-Start Thread

  1. Use the table or equation to determine the pitch, lead, and lead angle of the multi-start thread.
  2. Use a single form thread mill to helically interpolate the first thread at the correct lead. *The thread mill used must have a relief angle greater than that of the multi-start thread’s lead angle in order to machine the thread.
  3. Index to the next starting location and mill the remaining parallel thread/threads.

Click here for the full chart – starting on Page 2.

multi-start thread

 

 

 

 

Corner Engagement: How to Machine Corners

Corner Engagement

During the milling process, and especially during corner engagement, tools undergo significant variations in cutting forces. One common and difficult situation is when a cutting tool experiences an “inside corner” condition. This is where the tool’s engagement angle significantly increases, potentially resulting in poor performance.

Machining this difficult area with the wrong approach may result in:

  • Chatter – visible in “poor” corner finish
  • Deflection – detected by unwanted “measured” wall taper
  • Strange cutting sound – tool squawking or chirping in the corners
  • Tool breakage/failure or chipping

Least Effective Approach (Figure 1)

Generating an inside part radius that matches the radius of the tool at a 90° direction range is not a desirable approach to machining a corner. In this approach, the tool experiences extra material to cut (dark gray), an increased engagement angle, and a direction change. As a result, issues including chatter, tool deflection/ breakage, and poor surface finish may occur.

Feed rate may need to be lessened depending on the “tool radius-to-part radius ratio.”

corner engagement

More Effective Approach (Figure 2)

Generating an inside part radius that matches the radius of the tool with a sweeping direction change is a more desirable approach. The smaller radial depths of cut (RDOC) in this example help to manage the angle of engagement, but at the final pass, the tool will still experience a very high engagement angle.  Common results of this approach will be chatter, tool deflection/breakage and poor surface finish.

Feed rate may need to be reduced by 30-50% depending on the “tool radius-to-part radius ratio.”

corner engagement

Most Effective Approach (Figure 3)

Generating an inside part radius with a smaller tool and a sweeping action creates a much more desirable machining approach. The manageable RDOC and smaller tool diameter allow for management of the tool engagement angle, higher feed rates and better surface finishes. As the cutter reaches full radial depth, its engagement angle will increase, but the feed reduction should be much less than in the previous approaches.

Feed rate may need to be heightened depending on the “tool-to-part ratio.” Utilize tools that are smaller than the corner you are machining.

corner engagement

Ramping to Success

Poor tool life and premature tool failure are concerns in every machining application. Something as simple as tool path selection – and how a tool first enters a part – can make all the difference. Tool entry has a great deal of influence on its overall success, as it’s one of the most punishing operations for a cutter. Ramping into a part, via a circular or linear toolpath, is one of the most popular and oftentimes the most successful methods (Figure 1). Below, learn what ramping is, its benefits, and in which situations it can be used.

ramping

What is Ramping?

Ramping refers to simultaneous radial and axial motion of a cutting tool, making an angular tool path. Oftentimes, this method is used to approach a part when there is a need to create closed forms such as pockets, cavities, engravings, and holes. In doing so, the need to plunge with an end mill or drill to create a starting point is eliminated. Ramping is particularly important in micromachining where even the slightest imbalance in cutting forces can cause tool failure.

There are two types of ramping toolpaths: Linear and Circular (Figure 2 ).

ramping

Linear Ramping involves moving a cutting tool along two axes (the z-axis and one of the x, y axes). This method has significant more radial engagement with complementary increased cutting forces distributed across only two axes.

Circular Ramping (Helical Interpolation) has a spiral motion of the cutting tool that engages all three axes (x, y, and z axes). This method typically has less radial engagement on the cutting tool, with the cutting forces distributed across the three different axes. This is the recommended method, as it ensures the longest tool life.

Suggested Starting Ramp Angles:

Soft/Non-Ferrous Materials: 3° – 10°

Hard/Ferrous Materials 1° – 3°

Benefits of Ramping

When a tool enters the part via a Ramping method, it gradually increases in depth, preventing any shock loading on end mills. This reduces costs resulting from unnecessary tool breakage. Ramping produces smaller chips when compared to plunging, which makes chip evacuation faster and easier. As a result, cycle time can be decreased by running the end mill at faster parameters. Ramping also creates an extra space in the tool changer that would otherwise be occupied by a drill purposed with machining a starter hole.

Arcing

Similar to ramping in both method and benefit, arcing is another technique of approaching a workpiece (See Figure 3).

While ramping enters the part from the top, arcing enters from the side. The end mill follows a curved tool path (or arc) when milling, thus gradually increasing the load on the tool as the tool enters the part, as well as gradually decreasing the load as the tool exits the part. In this way, shock loading and possible tool breakage are avoided.

For more information on ramping, arcing, and other tool entry methods, please see Helical Solutions’ “Types of Tool Entry.” 

Climb Milling vs. Conventional Milling

There are two distinct ways to cut materials when milling: Conventional Milling (Up) and Climb Milling (Down). The difference between these two techniques is the relationship of the rotation of the cutter to the direction of feed. In Conventional Milling, the cutter rotates against the direction of the feed. During Climb Milling, the cutter rotates with the feed.

Conventional Milling is the traditional approach when cutting because the backlash, or the play between the lead screw and the nut in the machine table, is eliminated (Figure 1). Recently, however, Climb Milling has been recognized as the preferred way to approach a workpiece since most machines today compensate for backlash or have a backlash eliminator.

 


Key Conventional and Climb Milling Properties:

Conventional Milling (Figure 2)

  • Chip width starts from zero and increases which causes more heat to diffuse into the workpiece and produces work hardening
  • Tool rubs more at the beginning of the cut causing faster tool wear and decreases tool life
  • Chips are carried upward by the tooth and fall in front of cutter creating a marred finish and re-cutting of chips
  • Upwards forces created in horizontal milling* tend to lift the workpiece, more intricate and expansive work holdings are needed to lessen the lift created*

climb milling

 

Climb Milling (Figure 3)

  • Chip width starts from maximum and decreases so heat generated will more likely transfer to the chip
  • Creates cleaner shear plane which causes the tool to rub less and increases tool life
  • Chips are removed behind the cutter which reduces the chance of recutting
  • Downwards forces in horizontal milling is created that helps hold the workpiece down, less complex work holdings are need when coupled with these forces
  • Horizontal milling is when the center line of the tool is parallel to the work piece

climb milling


When to Choose Conventional or Climb Milling

Climb Milling is generally the best way to machine parts today since it reduces the load from the cutting edge, leaves a better surface finish, and improves tool life. During Conventional Milling, the cutter tends to dig into the workpiece and may cause the part to be cut out of tolerance.

However, though Climb Milling is the preferred way to machine parts, there are times when Conventional Milling is the necessary milling style. One such example is if your machine does not counteract backlash. In this case, Conventional Milling should be implemented. In addition, this style should also be utilized on casting, forgings or when the part is case hardened (since the cut begins under the surface of the material).

 

 

Dodging Dovetail Headaches: 7 Common Dovetail Mistakes

Cutting With Dovetails

While they are specialty tools, dovetail style cutters have a broad range of applications. Dovetails are typically used to cut O-ring grooves in fluid and pressure devices, industrial slides and detailed undercutting work. Dovetail cutters have a trapezoidal shape—like the shape of a dove’s tail. General purpose dovetails are used to undercut or deburr features in a workpiece. O-ring dovetail cutters are held to specific standards to cut a groove that is wider at the bottom than the top. This trapezoidal groove shape is designed to hold the O-ring and keep it from being displaced.

Avoiding Tool Failure

The dovetail cutter’s design makes it fragile, finicky, and highly susceptible to failure. In calculating job specifications, machinists frequently treat dovetail cutters as larger than they really are because of their design, leading to unnecessary tool breakage. They mistake the tool’s larger end diameter as the critical dimension when in fact the smaller neck diameter is more important in making machining calculations.

As the tools are downsized for micro-applications, their unique shape requires special considerations. When machinists understand the true size of the tool, however, they can minimize breakage and optimize cycle time.

Miniature Matters – Micro Dovetailing

As the trend towards miniaturization continues, more dovetailing applications arise along with the need for applying the proper technique when dovetailing microscale parts and features. However, there are several common misunderstandings about the proper use of dovetails, which can lead to increased tool breakage and less-than-optimal cycle times.

There are seven common mistakes made when dovetailing and several strategies for avoiding them:

1. Not Taking Advantage of Drop Holes

Many O-ring applications allow for a drop hole to insert the cutter into the groove. Take advantage of a drop hole if the part design allows it, as it will permit usage of the largest, most rigid tool possible, minimizing the chance of breakage (Figure 1).

dovetail cutters
Figure 1. These pictured tools are designed to mill a groove for a Parker Hannifin O-ring groove No. AS568A-102 (left). These O-rings have cross sections of 0.103″. There is a large variation in the tools’ neck diameters. The tool at right, with a neck diameter of 0.024″, is for applications without a drop hole, while the other tool, with a neck diameter of 0.088″, is for drop-hole applications. The drop-hole allowance allows application of the more rigid tool.

2. Misunderstanding a Dovetail’s True Neck Diameter.

The dovetail’s profile includes a small neck diameter behind a larger end-cutting diameter. In addition, the flute runs through the neck, further reducing the tool’s core diameter. (In the example shown in Figure 2, this factor produces a core diameter of just 0.014″.) The net result is that an otherwise larger tool becomes more of a microtool. The torque generated by the larger diameter is, in effect, multiplied as it moves to the narrower neck diameter. You must remember that excess stress may be placed on the tool, leading to breakage. Furthermore, as the included angle of a dovetail increases, the neck diameter and core diameter are further reduced. O-ring dovetail cutters have an included angle of 48°. Another common included angle for general purpose dovetails is 90°. Figure 3 illustrates how two 0.100″-dia. dovetail tools have different neck diameters of 0.070″ vs. 0.034″ and different included angles of 48° vs. 90°.

dovetail cutters
Figure 2. The dovetail tool pictured is the nondrop-hole example from Figure 1. The cross section illustrates the relationship between the end diameter of the tool (0.083″) and the significantly smaller core diameter (0.014″). Understanding this relationship and the effect of torque on a small core diameter is critical to developing appropriate dovetailing operating parameters.
dovetail cutters
Figure 3: These dovetail tools have the same end diameter but different neck diameters (0.070″ vs. 0.034″) and different included angles (48° vs. 90°).

3. Calculating Speeds and Feeds from the Wrong Diameter.

Machinists frequently use the wrong tool diameter to calculate feed rates for dovetail cutters, increasing breakage. In micromachining applications where the margin for error is significantly reduced, calculating the feed on the wrong diameter can cause instantaneous tool failure. Due to the angular slope of a dovetail cutter’s profile, the tool has a variable diameter. While the larger end diameter is used for speed calculations, the smaller neck diameter should be used for feed calculations. This yields a smaller chip load per tooth. For example, a 0.083″-dia. tool cutting aluminum might have a chip load of approximately 0.00065 IPT, while a 0.024″-dia. mill cutting the same material might have a 0.0002-ipt chip load. This means the smaller tool has a chip load three times smaller than the larger tool, which requires a significantly different feed calculation.

4. Errors in Considering Depth of Cut.

In micromachining applications, machinists must choose a depth of cut (DOC) that does not exceed the limits of the fragile tool. Typically, a square end mill roughs a slot and the dovetail cutter then removes the remaining triangular-shaped portion. As the dovetail is stepped over with each subsequent radial cut, the cutter’s engagement increases with each pass. A standard end mill allows for multiple passes by varying the axial DOC. However, a dovetail cutter has a fixed axial DOC, which allows changes to be made only to the radial DOC. Therefore, the size of each successive step-over must decrease to maintain a more consistent tool load and avoid tool breakage (Figure 4).

dovetail cutters
Figure 4: In microdovetailing operations, increased contact requires diminishing stepover to maintain constant tool load.

5. Failing to Climb Mill.

Although conventional milling has the benefit of gradually loading the tool, in low-chip load applications (as dictated by a dovetail cutter’s small neck diameter) the tool has a tendency to rub or push the workpiece as it enters the cut, creating chatter, deflection and premature cutting edge failure. The dovetail has a long cutting surface and tooth pressure becomes increasingly critical with each pass. Due to the low chip loads encountered in micromachining, this approach is even more critical to avoid rubbing. Although climb milling loads the tool faster than conventional milling, it allows the tool to cut more freely, providing less deflection, finer finish and longer cutting-edge life. As a result, climb milling is recommended when dovetailing.

6. Improper Chip Flushing.

Because dovetail cuts are typically made in a semi-enclosed profile, it is critical to flush chips from the cavity. In micro-dovetailing applications, chip packing and recutting due to poorly evacuated chips from a semi-enclosed profile will dull the cutter and lead to premature tool failure. In addition to cooling and lubricating, a high-pressure coolant effectively evacuates chips. However, excessive coolant pressure placed directly on the tool can cause tool vibration and deflection and even break a microtool before it touches the workpiece. Take care to provide adequate pressure to remove chips without putting undue pressure on the tool itself. Specific coolant pressure settings will depend upon the size of the groove, the tool size and the workpiece material. Also, a coolant nozzle on either side of the cutter cleans out the groove ahead of and behind the cutter. An air blast or vacuum hose could also effectively remove chips.

7. Giving the Job Away.

As discussed in item number 3, lower chip loads result in significantly lower material-removal rates, which ultimately increase cycle time. In the previous example, the chip load was three times smaller, which would increase cycle time by the same amount. Cycle time must be factored into your quote to ensure a profitable margin on the job. In addition to the important micro-dovetailing considerations discussed here, don’t forget to apply the basics critical to all tools. These include keeping runout low, using tools with application-specific coatings and ensuring setups are rigid. All of these considerations become more important in micro-applications because as tools get smaller, they become increasingly fragile, decreasing the margin of error. Understanding a dovetail cutter’s profile and calculating job specifications accordingly is critical to a successful operation. Doing so will help you reach your ultimate goal: bidding the job properly and optimizing cycle time without unnecessary breakage.

This article was written by Peter P. Jenkins of Harvey Tool Company, and it originally appeared in MicroManufacturing Magazine.