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8 Unique Facts About Thread Forming Taps

Unlike most CNC cutting tools, Thread Forming Taps, otherwise known as Form Taps, Forming Taps, or Roll Taps, work by molding the workpiece rather than cutting it. Because of this, Form Taps do not contain any flutes, as there is no cutting action taking place, nor are there any chips to evacuate. Below are 8 unique facts of Thread Forming Taps (and some may surprise you).

1. Chips Aren’t Formed

When using a Form Tap, chips are not formed, nor is any part material evacuated (Yes, you read that right). With thread forming, the tool is void of any flutes, as chip evacuation is not a concern. Form Taps quite literally mold the workpiece, rather than cut it, to produce threads. Material is displaced within a hole to make way for the threads being formed.

2. Cutting Oils Allow for Reduced Friction & Heat Generation

Did you know that Thread Forming Taps require good lubrication? But why is that the case if chips are not being evacuated, and how does lubrication enter the part with such a limited area between the tool and the perimeter of the hole being threaded? Despite the fact that chips aren’t being formed or evacuated, cutting oils aid the Form Tap as it interacts with the part material, and reduces friction and heat generation. Lube vent grooves are narrow channels engineered into the side of Forming Taps that are designed to provide just enough room for lubricant to make its way into – and out of – a part.

titan thread forming tool

Not all materials are well suited for Thread Forming Taps. In fact, attempting to use a tap in the wrong material can result in significant part and tool damage. The best materials for this unique type of operation include aluminum, brass, copper, 300 stainless steel, and leaded steel. In other words, any material that leaves a stringy chip is a good candidate for cold forming threads. Materials that leave a powdery chip, such as cast iron, are likely too brittle, resulting in ineffective, porous threads.

4. Threads Produced Are Stronger Than Conventional Tapping Threads

Thread forming produces much stronger threads than conventional tapping methods, due to the displacements of the grain of the metal in the workpiece. Further, cutting taps produce chips, which may interfere with the tapping process.

5. Chip Evacuation is Never a Concern With Thread Forming

In conventional tapping applications, as with most machining applications, chip evacuation is a concern. This is especially true in blind holes, or holes with a bottom, as chips created at the very bottom of the hole oftentimes have a long distance to travel before being efficiently evacuated. With form taps, however, chip removal is never a concern.

6. Form Taps Offer Extended Tool Life

Thread Forming Taps are incredibly efficient, as their tool life is substantial (Up to 20x longer than cutting taps), as they have no cutting edges to dull. Further, Thread Forms can be run at faster speeds (Up to 2x faster than Cutting Taps).

Pro Tip: To prolong tool life even further, opt for a coated tool. Titan USA Form Taps, for example, are fully stocked in both uncoated and TiN coated styles.

titan thread forming tools

7. A Simple Formula Will Help You Find the Right Drill Size

When selecting a Tap, you must be familiar with the following formula, which will help a machinist determine the proper drill size needed for creating the starter hole, before a Thread Forming Tap is used to finish the application:

Drill Size = Major Diameter – [(0.0068 x desired % of thread) / Threads Per Inch]
Drill Size (mm) = Major Diameter – [(0.0068 x desired % of thread x pitch (mm)]

8. Thread Forming Taps Need a Larger Hole Size

  1. Thread Form Taps require a larger pre-tap hole size than a cutting tap. This is because these tools impact the sides of the hole consistently during the thread forming process. If the pre-tap hole size is too small, the tool would have to work too hard to perform its job, resulting in excessive tool wear, torque, and possible breakage.

As an example, a ¼-20 cut tap requires a #7 drill size for the starter hole, whereas a ¼-20 roll tap requires a #1 drill size for 65% thread.

R & S Machining – Featured Customer

Located in St. Louis, Missouri, R & S Machining specializes in 4 & 5 axis machining and manufacturing of aerospace components. Since R & S was founded in 1992, they have instilled a spirit of hard work and determination to exceed customer expectations. Equipped with up-to-date machines and automation, R & S Machining has high-quality equipment to keep them as efficient as possible to stay ahead of the competition. The highly skilled men and women operating the manufacturing facility are committed to a high quality standard to meet all customer requirements. Because of this commitment, R & S Machining has been able to expand its facilities in the past four years by more than 225,000 square feet.

We were able to get in touch with Matthew Roderick, the lead programmer for R & S Machining. Matthew took some time out of his busy schedule to answer some questions about R & S Machining, and how the company continues to grow.

Can you tell us a little about R & S Machining?

R & S Machining is dedicated to continual improvement and growth. We strive to buy very high quality machines and tooling. We also equip most of our machines with automation. Whether it is a bar feeder, pallet changer, FMS, or robot, nearly all our machines have some form of automation to increase our lights out production. In the past 4 years, we have built a new facility and purchased a new facility. We have grown by more than 225,000 square feet and 35 employees in this timespan. With the backing of our ownership, continued success and relationships with our customers, very dedicated employees, and high-quality reliable manufacturing equipment, we are in a league of our own and continue to strive towards our goal of becoming the powerhouse manufacturing company of the Midwest.

R & S Machining currently uses Hermie, Okuma, Makino, and Kenichi machines in the facility, while utilizing CAM/CAD software such as Siemens NX, Catia, and Mastercam.

How did R & S get into Aerospace and Defense Manufacturing?

Our president worked at Boeing for 10 years. When he left to start his own company, we were given an opportunity with the Boeing Company to manufacture aerospace and defense components based on the quality of work that our President produced during his time with them. We continued to produce high quality products with an emphasis on on-time delivery and the rest is history.

What sets R & S apart from the rest of the competitors?

We take on all the work that our competitors no quote or refuse to do. The complexity of parts that flow through this shop is like no other place. We believe there is no other company that can produce the complexity level of parts that we make in the time frames we are given by our customers.

Customer satisfaction is maintained through effectively applying the quality system. Continued training and process review enable R & S Machining to meet customers’ ever-changing requirements. 

What is your favorite project you have had come through the shop?

We manufacture Inlet Ducts for a variety of Fighter Jets. The complexity of these parts is unmatched and the creativity in programming the parts in the CAM system has to be at its peak. Some of these parts require programs of 600+ toolpaths with a majority of them being full 5axis simultaneous paths. Then, when you get to see the machine throwing a 1,100 pound block around like it’s nothing at 2000 IPM in full 5axis simultaneous motion, it’s pretty humbling.

What is your connection with the Missouri SkillsUSA Competition?

SkillsUSA is a nonprofit national education association that serves middle school, high school, and college/postsecondary students preparing for careers in trade, technical, and skilled service (including health) occupations. SkillsUSA’s mission is to empower its members to become world class workers, leaders, and responsible American citizens. It emphasizes total quality at work—high ethical standards, superior work skills, lifelong education, and pride in the dignity of work.

Over the past 4 years, we have had many of our employees participate and win in the competition. We have had 5 employees win the district championship, 5 employees win the state championship, and 3 employees win the national championship.

Why is high quality tool performance important to you?

We rely on high quality tool performance to meet the tolerancing demands of our customers. Our tolerances range from hole tolerances of +.002″/-.001″, thickness tolerances of +-.01″, profile tolerances of .03″, critical hole tolerances of +-.0002″, and critical hole true position tolerances of .007″. We also rely heavily on lights-out run time overnight, so having a high quality tool that you know is still going to be cutting effectively in the morning and throughout the night is critical to our operation.

We had a 50+ quantity stainless steel job that we were only getting 2-3 parts per tool using tools from a different manufacturer. We changed our tool to a Helical endmill and left everything else the same and made over 30 parts before having to change out the tool.

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

There are tons of cool and flashy things out there, but you can not skip the fundamentals. They are the building block to your entire career and they are the concepts you will use every single day. Use the technology to further your skills, not the basis of your skills. At the end of the day, you always have to know feeds and speeds, depth of cuts, work holding, and what you can get away with.

Is there anything else you would like to share with the In The Loupe community?

Helical tooling is unmatched in the HEM hard metal category. These tools have changed the way we manufacture parts and give us the confidence we need to accomplish our high precision and complex parts.

If you want to see what is next for R & S Machining or reach out and ask them some questions, you can follow them on Instagram @randsmachine.

Defiant CNC – Featured Customer

Twenty years ago, Jeremy Taylor worked as a Tool and Die Apprentice and was well on his way to earning his Journeyman Certification, when he fell in with the wrong crowd and found himself in trouble, criminally. As a result, he found himself facing a lengthy prison sentence but was determined to make his time incarcerated as constructive as possible. During his sentence, he earned his undergraduate and MBA degrees, taught himself Spanish and Italian, and used his limited access to computers to stay updated on all things CNC machining, including the evolution of tool making and advanced manufacturing.

Today, Taylor owns Defiant CNC, a 2-year-old machine shop located in Orlando, Florida, that specializes in performing a wide variety of machining operations, including CNC Milling, CNC turning, laser engraving, finishing, quality control, CAM/CAD, inventory management, technical drawings, and ERP services. Defiant CNC machines everything from components for underwater welding robots to tools for helicopter repair kits, to even tools for pastry decorating and jewelry making.

Along with owning his business, Taylor also spends his time working with The Community, a company that focuses on preparing prisoners to reenter society.

We spoke with Taylor to learn more about how he changed his life’s trajectory; his new business; the ERP system he built, himself; and what he values most in CNC tooling, among other topics.

How did you first get started in machining?

I started off as a Tool and Die Apprentice. I was making tremendous progress towards my Journeyman Certification until I got myself into trouble. I had done a great job of learning very sophisticated toolmaking techniques and CNC programming/machining. Unfortunately, when I was a few months away from obtaining my journeyman’s card, I was incarcerated for 14 years. However, I utilized that time to significantly change my life trajectory. While in prison, I taught myself Spanish and Italian, kept as up to speed as I could (given very limited access to computers) on the evolution of tool making, CNC machining, advanced manufacturing, computer hardware, and software, completed both an undergraduate degree and an MBA via a mixture of mail and online access.

Today I am a completely different person than the one who wasted the great opportunities I had before my imprisonment. Somewhere along the line during the time when I was 18-19 or so, I fell in with the wrong people and took a path that led to me wasting what should have been the best years of my life. Rather than give up, I used that time while confined to continue my education and prepare myself for a productive role in society after my release. Getting back into machining played a huge role in my current success. Defiant CNC has only been in business for a little over two years, but the best is yet to come.

What machines are in your shop?

Defiant CNC currently has 4 mills: Doosan DNM 4500, Chevelier QP 2040, Toyoda Stealth 1365, and a Manual Bridgeport Mill. We use Fusion 360 on all of our milling machines. We also have 5 lathes: Emco Maier 365 Y, Miyano BND-51S, Miyano BND-20S5, Miyano BND-34S. and a Miyano BND-42S. Finally, we have our two support machines, a Cosen MH-1016JA Bandsaw and a Boss FMS Laser for Desktop Fiber Marking.

What industries have you worked with?

We have worked with a large variety of industries, including aerospace, defense, automotive, commercial, and medical. Working in these industries allows us to machine in all different materials: Aluminum (7075, 6061, and 2024), Stainless Steel (303, 304, and 316), and Steel (1018, 4140, and 1045).

What sets Defiant CNC apart from the competition?

We provide an array of machining-related services including milling, turning, CAD design, engineering, and laser engraving in-house. We also provide a number of services through vetted partners such as heat treating, welding, and plating. However, what sets us apart from the rest of the competition is the Enterprise Resource Planning (ERP) system that I built, which is customized specifically for our shop. Not only does it allow us to streamline our operations, but it also allows us to give that something extra to our customers. I create portals and give our customers access to all their past and present jobs with us. They can check the status of any of their jobs as they move through the production process. We take just as much care managing every aspect of the business as we do machining parts.

Typically in small-to-medium-sized shops, the data structure is to create a series of customer-job-part revision folders, and put the customer data there. This data structure is rarely planned for growth. I created an Enterprise Resource Planning (ERP) system using Airtable, along with other API-friendly applications, because the software has Product Data Management (PDM) built into it. PDM is the architecture of the data storage system which, in a nutshell, is the organization, storage, and retrieval of any data that might be tied to a manufacturing process. Since Airtable has a built-in PDM system, we are able to store all our CAM files, G-code, setup documents, tool data (where we log important data about our Helical and Harvey tools), fixture data, and any other data that needs to be tied to a step for making a part. We now have a place to bring together product data (images, instructions, inventory, links, etc), customer information (CRM data), data on sales, marketing development and deployment, a schedule, and more, all in one place. All of the integrations and automations that I built saves hours of manual work and prevents a multitude of mistakes.

What is your favorite job you have worked on?

I just finished a production run on a job where I completed 12 pieces of two different parts out of hardened 17-4 stainless from start to finish. The cycle time was just over four hours. Each part required three operations after the stock was sawed and heat treated. I designed, modeled, and made two sets of fixtures for each operation in order to load one set while the other was being machined.

When have Harvey or Helical products helped your business?

A majority of the endmills that we stock are Harvey Tool and Helical products. We utilize Fusion 360, which has a tool library full of Harvey Tool and Helical products. About a week ago, we purchased some Harvey Tool flat bottom endmills which saved substantial time on a large production run because we no longer had to circular interpolate a hole. Whenever we are in a pinch and need a tool quickly, Helical Solutions and Harvey Tool always come through.

Why is high quality tooling important to you?

High quality tools allow us to spend more time machining and less time changing tools. Our go-to tool is Helical’s 3 flute – 40-degree helix with ZPlus, whether we need 1/8 end mills or 5/8 endmills, they get the job done.

What advice do you have for others who want to try High Efficiency Milling?

Consider the material that you are cutting. Consult with your tooling vendor and/or documentation on their website to obtain a starting point and go from there. Helical Solutions has great information on their website and on their social media accounts, with regard to their products. It is worth consulting these sources when utilizing their tools.

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

Learning needs to be continuous. Don’t just expect to learn everything that you need to know in one place. Constantly increment your skills in every aspect of machining.

Is there anything else you would like to share with the “In The Loupe” community?

I am grateful for the opportunity to talk about my experiences with Harvey Tool and Helical products and my business. I use Harvey Tool and Helical products because they work well. I will continue to document my usage of their products on my website DefiantCNC.com, as well as my company’s social media accounts (@defiantcnc on Instagram, LinkedIn, and Facebook). Be sure to check them out.

CNC Machining & 3D Printing: A Hybrid Approach to Precision Manufacturing

With recent advancements in 3D printing capabilities, it is becoming easier for manufacturers to use additive manufacturing to create parts from a wide variety of materials, including polymers like ABS, TPE, and PLA as well as carbon fiber composites, nylon, and polycarbonates. Even pricey metals like Titanium, Stainless Steel, and Inconel are becoming increasingly common in the world of additive manufacturing as well.

There is no doubt that the additive manufacturing space will continue to develop and grow in the coming years, but will it render subtractive manufacturing methods like CNC Machining obsolete? Absolutely not. In fact, precision CNC machining is likely more important to the additive manufacturing process than you may think, as a new process called “hybrid manufacturing” is quickly taking hold in the industry.

3d printing metal
3D printing of metal parts is becoming more common, but subtractive manufacturing is an important part of manufacturing precision additive parts.

Additive Manufacturing vs. Subtractive Manufacturing

Before implementing a hybrid manufacturing approach, it is important to understand the pros and cons of each method. Here is a quick breakdown of both additive and subtractive manufacturing, and the benefits and drawbacks of each.

Additive ManufacturingSubtractive Manufacturing
Adds material layers to create partsRemoves material layers to create parts
Slower process, better for small production runsFaster process, better for large production runs
Better for smaller partsBetter for larger parts
Rough surface finish that requires significant post-operation finishingMore definied surface finish with minimal post-operation finishing required
Less precise part tolerancesAble to hold extremely precise part tolerances
Cheaper material costsMore expensive material costs
Less material wasteMore material waste
Intricate details easier to createIntricate details can require complex programs and additional capabilities (5 axis)

Using CNC Machining to Create Precise 3D Printed Parts

Looking at the chart above, you will notice that one of the key differences between additive manufacturing and subtractive manufacturing is the surface finish and tolerances that can be achieved with each method. This is where a hybrid approach to additive manufacturing can be extremely beneficial.

As parts come off the printer, they can be quickly moved into a CNC machine with a program designed for part completion. The CNC machine will be able to get 3D printed parts down to the tight tolerances required by many industries and reach the desired surface finish. Advanced finishing tools and long reach, tapered tools from brands like Harvey Tool can easily machine the tight geometries of 3D printed parts, while extremely sharp diamond-coated tooling and material-specific tools designed for plastics and composites can work to create a beautiful, in-tolerance finished part regardless of the material.

long reach end mill
Long reach tools can easily machine hard to reach, intricate part details on 3D printed parts.

By designing a workflow like this in your shop, you can spend less time worrying about the precision of printed parts by adding in subtractive operations to keep material costs low, create less waste, and keep parts in tight tolerances for precision machining excellence.

Using 3D Printing to Increase CNC Machining Efficiency

If your shop is focused completely on subtractive manufacturing methods, you are probably thinking that there is no need for an additive option in your shop. Can’t a CNC machine create everything a 3D printer can, and in less time? Not necessarily. Again, by using the two methods together and taking a hybrid approach, you may be able to lower your manufacturing and material costs.

For example, you could machine the bulk of a part with typical subtractive machines, which would likely take a very long time using additive methods. Then you can go back to that part with a 3D printer to add intricate features to the part that may take complex programming and hours of planning on a subtractive machine. An impeller is a great example, where the bulk of that part can be machined, but the tricky fins and blades could be printed onto the part, and then finished back on the CNC machine.

3d printed metal parts
3D printed impeller waiting for finishing operations

The ability of additive machines to literally “add-on” to a part can also make for a cheaper approach to part design. Instead of using expensive materials like Inconel or Titanium to machine an entire part, portions of the part that do not require extreme heat resistance could be machined out of cheaper steel, while the heat resistant portions using expensive materials can be added later through additive methods.

Hybrid Manufacturing Machines

As hybrid manufacturing workflows become more popular, so do new hybrid manufacturing machines. These hybrid machines are all-in-one machines where both additive and subtractive manufacturing can be performed in a single setup. Many of these machines offer metal 3D printing as well as multi-axis machining capabilities, ready for even the most complex parts thrown their way. With a bit of customization, large-scale 3D printing machines or CNC mills can be retrofit to allow for hybrid manufacturing with add-ons from companies like Hybrid Manufacuring Technologies.

hybrid manufacturing machines
Example of a hybrid machine add-on from Hybrid Manufacturing Technologies, featuring 3D printing spindles and milling tools in the same machine carousel.

As manufacturing and design techniques get progressively “smarter” with CAM/CAD programs offering generative design and artificial intelligence, these hybrid machines could become a new standard in high-end machine shops working in advanced manufacturing industries like aerospace, medical, defense, and the mold, tool & die market.

Overall, in 2021 we are still early on in this new revolution of hybrid machining and advanced design methods, but it is important to understand the role that adding a CNC machine could have in your additive-focused shop, and vice versa. By combining additive and subtractive together, shops can mitigate the cons of each method and take full advantage of the benefits of having both options available on the shop floor.

Workshops for Warriors – Featured Customer

In 2008, Hernán Luis y Prado, a United States Navy officer, noticed his fellow service members looking for a successful path in life after service. Hernán decided he needed to make a change. He set out to make a difference for his fellow service members by starting Workshops for Warriors, a state-licensed, board governed, fully audited, nonprofit school. Its mission is to provide quality training, accredited educational programs, and opportunities for its students to earn third-party nationally recognized credentials to enable Veterans, transitioning service members, and others to be successfully trained and placed in their chosen advanced manufacturing career field.

We had the honor of speaking with Marine Veteran Scott Leoncini, an instructor at Workshops for Warriors, about the accomplishments and amazing work Workshops for Warriors does for our Veterans.

What Does Workshops for Warriors Offer for Our Veterans?

Workshops for Warriors offers two primary tracks of training, both taught by Veterans: welding and machining, Scott explained. After choosing a track, students become a part of the 16-week accelerated program. Those with only a minimum of four months and one nationally-recognized certification can walk across the shipyards and gain employment. Workshops for Warriors remains committed to providing free training to Veterans who do not have access to living-wage jobs. U.S. Veterans often face challenges as they transition to civilian life, including significant barriers to civilian employment. In addition to the hard technical skills, our students are also learning soft skills such as attitude, communication, work ethic, teamwork, time management, problem-solving, critical thinking, and conflict resolution.

A proven path into a rewarding career can eliminate problems like unemployment, homelessness, broken families, and suicide. The problem of Veteran unemployment does not have easy, short-term solutions. Workshops for Warriors is uniquely positioned to expand proven innovative techniques to give Veterans marketable employment that will allow them to build careers and families. 

How Did You Find Workshops for Warriors and Become an Instructor?

After I left the Marines in 2009, after serving two tours in Iraq as a combat engineer, I desired an action-packed career. I thought my best option was to start a career in law enforcement. I got a job at a security company and worked there for a few years. During this time, a close friend of mine tragically passed away in a helicopter crash, leaving behind his pregnant wife. This made me reevaluate my current life with my wife and two children. I decided I didn’t need that action-packed career, and that my family comes before anything.

Another friend of mine actually told me about Workshops for Warriors and how it was giving him career skills in welding, and he talked about a machining program. When I showed up, I had no idea what was in store for me. I started learning all about CNC machines, and how to program and run these things. It was eye-opening and I was having a great time. After my first semester, I was asked to become a teacher’s assistant and I’ve been teaching here now for almost five years.

Where Does Your Passion for Teaching Come From?

I love teaching Veterans and helping them transition so they don’t have to go through the same five years I did of, “What am I going to do with my life?” I’ve gone through the same situation a lot of the people coming to us are currently in.

I think that there are three fundamentals that anyone looking for a career or path can apply to their lives and be successful. You have to show up on time, you have to work hard, and you have to be willing to learn. I didn’t know anything about machinery when I first got into this field. When I went through it as a student myself, I applied those three things to my work habits, and now I’m an instructor. I had pigeonholed myself for a long time. But you have to recognize that there’s always something else, something up next and that’s what I want to help teach the Veterans who come through here.

What Courses Does Workshops for Warriors Provide?

We offer many different courses, including CAD courses in Solidworks and CAM courses in Mastercam, and we offer welding courses for Gas Metal and Flux Cored Arc Welding. We also offer advanced training in Flowmaster Programming and Waterjet Operation, 3D Printing, and Robotics. With these courses, we offer many credentials to start a real career. The machining program is accredited by the National Institute for Metalworking Skills (NIMS). NIMS is recognized by the United States Department of Education. The welding program is accredited by the American Welding Society (AWS), which is the worldwide leader in certification programs for the welding industry.

Thanks to private donors, Veterans and transitioning service members are able to become trained and certified in our advanced manufacturing programs. Students can apply to enter one of our programs, or take specific classes that meet their needs.

What Jobs Have You Seen Veterans Acquire After Workshops for Warriors?

We have seen many success stories from Veterans once they leave Workshops for Warriors. One Veteran, in particular, visited us in search of direction in 2019. The machining program had one spot left for the semester, so he took it. He is now certified in machining and welding. He entered a job market that was struggling after his graduation. But he still had a job lined up with 5th Axis Machining in San Diego. His future plans are to own his own business to support his family.

How Could People Help Support Workshops for Warriors?

They can donate directly to us on our website, or on our Facebook page. Or, people looking to help support us can reach out to us by email, [email protected], or by calling us at 619-550-1620, with any questions. We also accept equipment donations for each program, welding, and machining. You can also support us by following on Facebook, Instagram, Twitter, LinkedIn, YouTube, or our newsletter.

What Advice Would you Give to Anyone Looking to Start a Career Path?

After leaving the service, I fell into a depression. I kept thinking, “I’ll never be as good as I was back then.” It was hard to not have “Marine” be the primary part of my identity, so I became blinded by my obsession with still being the superhero kicking down doors. Don’t paint yourself into a corner. Be flexible and make sure to show up on time, work hard, and be willing to have an open mind and ready to learn. Test your comfort zone. When I left the service, I only knew how to be the man with the gun. Workshops for Warriors gave me a chance to be more than that – it gave me a direction in life. I now get to do what I love and help my fellow Veterans.

To learn more about Workshops for Warriors and their mission you can visit their website or follow them on Instagram, Facebook, LinkedIn or Twitter.

The Secret Mechanics of High Feed End Mills

A High Feed End Mill is a type of High-Efficiency Milling (HEM) tool with a specialized end profile that allows the tool to utilize chip thinning to have dramatically increased feed rates. These tools are meant to operate with an extremely low axial depth so that the cutting action takes place along the curved edge of the bottom profile. This allows for a few different phenomena to occur:

  • The low lead angle causes most of the cutting force to be transferred axially back into the spindle. This amounts to less deflection, as there is much less radial force pushing the cutter off its center axis.
  • The extended curved profile of the bottom edge causes a chip thinning effect that allows for aggressive feed rates.

The Low Lead Angle of a High Feed End Mill

As seen in Figure 1 below, when a High Feed End Mill is properly engaged in a workpiece, the low lead angle, combined with a low axial depth of cut, transfers the majority of the cutting force upward along the center axis of the tool. A low amount of radial force allows for longer reaches to be employed without the adverse effects of chatter, which will lead to tool failure. This is beneficial for applications that require a low amount of radial force, such as machining thin walls or contouring deep pockets.

high feed mill roughing
Figure 1: Isometric view of a feed mill engaged in a straight roughing pass (left), A snapshot front-facing view of this cut (right)

Feed Mills Have Aggressive Feed Rates

Figure 1 also depicts an instantaneous snapshot of the chip being formed when engaged in a proper roughing tool path. Notice how the chip (marked by diagonal lines) thins as it approaches the center axis of the tool. This is due to the curved geometry of the bottom edge. Because of this chip thinning phenomenon, the feed of the tool must be increased so that the tool is actively engaged in cutting and does not rub against the workpiece. Rubbing will increase friction, which in turn raises the level of heat around the cutting zone and causes premature tool wear. Because this tool requires an increased chip load to maintain a viable cutting edge, the tool has been given the name “High Feed Mill.”

high feed end mill ad

Other Phenomena Due to Curved Geometry of Bottom Edge

The curved geometry of the bottom edge also sanctions for the following actions to occur:

  • A programmable radius being added to a CAM tool path
  • Scallops forming during facing operations
  • Different-shaped chips created during slotting applications, compared to HEM roughing

Programmable Radius

Helical Solutions’ High Feed End Mills has a double radius bottom edge design. Because of this, the exact profile cannot be easily programmed by some CAM software. Therefore, a theoretical radius is used to allow for easy integration.  Simply program a bullnose tool path and use the theoretical radius (seen below in Figure 2) from the dimensions table as the corner radius.

high feed mill programmable radius
Figure 2: Programmable radius of a double radius profile tool

Managing Scallops

A scallop is a cusp of material left behind by cutting tools with curved profiles. Three major factors that determine the height and width of scallops are:

  1. Axial Depth of Cut
  2. Radial Depth of Cut
  3. Curvature of Bottom Edge or Lead Angle

Figure 3 below is a depiction of the scallop profile of a typical roughing cut with a 65% radial step over and 4% axial depth of cut. The shaded region represents the scallop that is left behind after 2 roughing passes and runs parallel to the tool path.

roughing cut scallop profile
Figure 3: Back view of roughing cut with a 65% radial step over

Figures 4 and 5 show the effects of radial and axial depth of cuts on the height and width of scallops. These figures should be viewed in the context of Figure 3. Percentage by diameter is used rather than standard units of measurement to show that this effect can be predicted at any tool size. Figure 4 shows that a scallop begins to form when the tool is programmed to have a radial step over between 35% and 40%. The height increases exponentially until it is maximized at the axial depth of cut. Figure 5 shows that there is a linear relationship between the radial step over and scallop width. No relationship is seen between scallop width and axial depth of cut as long as ADOC and the radius of curvature of the bottom cutting edge remains consistent.

graph of scallop height versus depth of cut
Figure 4: Graph of Scallop Height vs. Depth of Cut
graph of scallop width versus depth of cut
Figure 5: Scallop Width vs. Depth of Cut

From the graphs in Figures 4 and 5 we get the following equations for scallop dimensions.

Notes regarding these equations:

  • These equations are only applicable for Helical Solutions High Feed End Mills
  • These equations are approximations
  • Scallop height equation is inaccurate after the axial depth of cut is reached
  • RDOC is in terms of diameter percentage (.55 x Diameter, .65 x Diameter, etc…)

Shop Helical Solutions’ Fully Stock Selection of High Feed End Mills

Curvature of the Bottom Edge of High Feed End Mills

The smaller the radius of curvature, the larger the height of the scallop. For example, the large partial radius of the Helical Solutions High Feed End Mill bottom cutting edge will leave a smaller scallop when compared to a ball end mill programmed with the same tool path. Figure 6 shows a side by side comparison of a ball end mill and high feed mill with the same radial and axial depth of cut. The scallop width and height are noticeably greater for the ball end mill because it has a smaller radius of curvature.

feed mill versus ball end mill
Figure 6: Scallop diagram of High Feed Mill and Ball End Mill with the same workpiece engagement

Full Slotting

When slotting, the feed rate should be greatly reduced relative to roughing as a greater portion of the bottom cutting edge is engaged. As shown in Figure 7, the axial step down does not equate to the axial engagement. Once engaged in a full slot, the chip becomes a complex shape. When viewing the chip from the side, you can see that the tool is not cutting the entirety of the axial engagement at one point in time. The chip follows the contour on the slot cut in the form of the bottom edge of the tool. Because of this phenomenon, the chip dips down to the lowest point of the slot and then back up to the highest point of axial engagement along the side. This creates a long thin chip that can clog up the small flute valleys of the tool, leading to premature tool failure. This can be solved by decreasing the feed rate and increasing the amount of coolant used in the operation.

high feed mill chip formation
Figure 7: Formation of a chip when a feed mill is engaged in a full slotting operation.

In summary, the curved profile of the bottom edge of the tool allows for higher feed rates when high feed milling, because of the chipping thinning effect it creates with its low lead angle. This low lead angle also distributes cutting forces axially rather than radially, reducing the amount of chatter that a normal end mill might experience under the same conditions. Machinists must be careful though as the curved bottom edge also allows for the formation of scallops, requires a programmable radius when using some CAM packages, and make slotting not nearly as productive as roughing operations.

Causes & Effects of Built-Up Edge (BUE) in Turning Applications

In turning operations, the tool is stationary while the workpiece is rotating in a clamped chuck or a collet holder. Many operations are performed in a lathe, such as facing, drilling, grooving, threading, and cut-off applications. it is imperative to use the proper tool geometry and cutting parameters for the material type that is being machined. If these parameters are not applied correctly in your turning operations, built-up edge (BUE), or many other failure modes, may occur. These failure modes adversely affect the performance of the cutting tool and may lead to an overall scrapped part.

When inspecting a cutting tool under a microscope or eye loupe, there are several different types of turning tool failure modes that can be apparent. Some of the most common modes are:

  • Normal Flank Wear: The only acceptable form of tool wear, caused by the normal aging of a used cutting tool and found on the cutting edges.
    • This abrasive wear, caused by hard constituents in the workpiece material, is the only preferred method of tool wear, as it’s predictable and will continue to provide stable tool life, allowing for further optimization and increased productivity.
  • Cratering: Deformations found on the cutting face of a tool.
    • This tool mode is a chemical and heat failure, localized on the rake face area of the turning tool, or insert. This failure results from the chemical reaction between the workpiece material and the cutting tool and is amplified by cutting speed. Excessive Crater Wear weakens a turning tool’s cutting edge and may lead to cutting edge failure.
  • Chipping: Breaking of the turning tool along its cutting face, resulting in an inaccurate, rough cutting edge.
    • This is a mechanical failure, common in interrupted cutting or non-rigid machining setups. Many culprits can be to blame for chipping, including machine mishaps and tool holder security.
  • Thermal Mechanical Failure (Thermal Cracking): The cracking of a cutting tool due to significant swings in machining temperature.
    • When turning, heat management is key. Too little or too much heat can create issues, as can significant, fast swings in temperature (repeated heating and cooling on the cutting edge). Thermal Mechanical Failure usually shows in the form of evenly spaced cracks, perpendicular to the cutting edge of the turning tool.
  • Built-Up Edge (BUE): When chips adhere to the cutting tool due to high heat, pressure, and friction.

Effects of Built-Up Edge in Turning Application

A built-up edge is perhaps the easiest mode of tool wear to identify, as it may be visible without the need for a microscope or an eye loupe. The term built-up edge means that the material that you’re machining is being pressure welded to the cutting tool. When inspecting your tool, evidence of a BUE problem is material on the rake face or flank face of the cutting tool.

built up cutting edge on turning tools
Image Source: Carbide inserts Wear Failure modes. | machining4.eu, 2020

This condition can create a lot of problems with your machining operations, such as poor tool life, subpar surface finish, size variations, and many other quality issues. The reason for these issues is that the centerline distance and the tool geometry of the cutting edge are being altered by the material that’s been welded to the rake or flank face of the tool. As the BUE condition worsens, you may experience other types of failures or even catastrophic failure.                     

Causes of Built-Up Edge in Turning Applications

Improper Tooling Choice

Built-Up Edge is oftentimes caused by using a turning tool that does not have the correct geometry for the material being machined. Most notably, when machining a gummy material such as aluminum or titanium, your best bet is to use tooling with extremely sharp cutting edges, free cutting geometry, and a polished flank and rake face. This will not only help you to cut the material swiftly but also to keep it from sticking to the cutting tool.

various turning tools

Using Aged Tooling

Even when using a turning tool with correct geometry, you may still experience BUE. As the tool starts to wear and its edge starts to degrade, the material will start building up on the surface of the tool. For this reason, it is very important to inspect the cutting edge of a tool after you have machined a few parts, and then randomly throughout the set tool life. This will help you identify the root cause of any of the failure modes by identifying them early on.

Insufficient Heat Generation

Built-up edge can be caused from running a tool at incorrect cutting parameters. Usually, when BUE is an issue, it’s due to the speed or feed rates being too low. Heat generation is key during any machining application – while too much heat can impact a part material, too little can cause the tool to be less effective at efficiently removing chips.

4 Simple Ways to Mitigate BUE in Turning Applications

  1. When selecting a tool, opt for free cutting, up sharp geometries with highly polished surfaces. Selecting a tool with chipbreaker geometry will also help to divide chips, which will help to remove it from the part and the cutting surface.
  2. Be confident in your application approach and your running parameters. It’s always important to double-check that your running parameters are appropriate for your turning application.
  3. Make sure the coolant is focused on the cutting edge and increase the coolant concentration amount.
  4. Opt for a coated Insert, as coatings are specifically engineered for a given set of part materials, and are designed to prevent common machining woes.
solid carbide turning tool

Heavy Duty Racing – Featured Customer

Heavy Duty Racing is a manufacturing company based in Stafford, VA, that specializes in motocross, off-road motorcycle suspension, and 2-stroke engine modification. Its owner, Pete Payne, grew up racing motorcycles. Later in life, he even taught classes on how to race. Simply, Motocross and motorcycles became Pete’s passion.

Pete always looked for ways to enhance his motorcycle’s engine, but quickly realized that no shops in his area could design what he was looking for. To get access to the parts he would need, he would have to rely upon companies from far away, and would oftentimes be forced to wait more than three weeks for them to arrive. Because of this, Pete decided he would need to take part manufacturing into his own hands. He purchased a manual lathe, allowing him to make modifications to his two-stroke engines exactly how he wanted them. Quickly thereafter, Heavy Duty Racing was born.

Pete discussed with us his love of racing, how he first got into machining, the parts his shop has designed, and tips and tricks for new machinists.

Pete Payne Heavy Duty Racing

How did you get started in machining?

Since I was a kid I have been riding motorcycles and racing motocross. I went to a tech school in the ’80s and learned diesel technologies. When I realized nobody in this area could help design the engines I wanted to make, I decided I needed to learn how to do it myself. I have a friend, George, who is a retired mold and die maker that also worked on motorcycle engines, I asked him for some advice on how to get started. George ended up teaching me all about machining and working on engines. I really learned from failures, by trying new things, and doing it every day. I started Heavy Duty Racing in 1997 and we have been modifying and designing the highest performing engines since then.

turning motorcycle part on lathe

What machines and softwares are you using in your shop?

We currently have a Thormach PCNC 1100 and a Daluth Puma CNC Lathe (we call it The Beast, it’s angry and grumpy but it gets the job done). We also have a Bridgeport Mill, Manual Lathe, and a Tiggwell. When we were choosing software to use, they had to be easy and quick to learn. We weighed our options and decided to use Autodesk Fusion 360 about 5 years ago. We mostly machine cast iron and steel since most engines are made from those materials.

What sets Heavy Duty Racing apart from competitions?

We have a small hands-on approach and treat every part with care. We don’t have a cookie-cutter process so we are very flexible when it comes to customer needs. Since each part is different, we don’t have set prices and have custom quoting on each part. We value our customers and tailor every build to the rider, based on the weight, fuel, and skill level of the rider. We make unique components for each rider so they can have the best experience when they hop on their bike. We are just focused on letting people do what they love.

metal racing parts made by Heavy Duty Racing

What is the coolest project you have worked on?

In 2016, MX Tech Suspension in Illinois gave us the opportunity to build an engine for them to display at their event. We got to go to California to watch them demo the engine in front of thousands of people. It was very nerve-racking to watch it live but the experience was amazing. The engine was later featured on the cover of Motocross Action magazine. It was very cool to see something we dedicated so much hard time toward get that much recognition.

Why is high quality tooling important to you?

We are making really difficult machine parts so we need tools that can last. Micro 100 tooling lasts and does the job. The thread mills we use are 3-4 mm and 14 mm and they last longer than any competition out there. The thread mills do not chip like the competition and the carbide is super strong. Breaking a tool is not cheap, so to keep one tool in the machine for how long we have has really saved me in the long run. We found Micro 100 one day looking through our distributor’s catalog and decided to try some of their boring bars. After about 5 holes, we realized that these tools are the best we have ever used! Micro has had everything I’ve been looking for in stock and ready to ship, so we have yet to need to try out their custom tools.

Most engine tolerances are no more than .0005” taper. You need the tooling to hold tight tolerances, especially in engines. Just like with tooling, minimizing vibration is key to getting the engine to last longer. We need tight tolerances to maintain high quality and keep engines alive.

machined metal racing part

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

The same advice I’ve given to my son: Don’t be ashamed to start from the bottom and learn from the ground, up. Everybody wants to make cool projects, but you need to learn what is going on around you to master the craft. Learn the processes and follow the steps. It’s very easy to break a tool, ruin a part, or even hurt yourself. Don’t be scared of quality tools! Buying the cheap stuff will help you with one job, but the quality tools last and will save you in multiple situations.

Follow Heavy Duty Racing on Instagram, and go check out their website to see more about them!

Hybrid Machining – Featured Customer

Located in Holland, MI, Hybrid Machining uses machining skills combined with 3 different 3D printing technologies to manufacture complex projects. Hybrid Machining is a manufacturing company that can take the customer’s design from start to finish, allowing customers to dictate their path. Rather than focusing on a single product, Hybrid has listened to customer needs and presented solutions that, in many cases, customers didn’t know were possible. Jeff Robinson, the owner, took some time out of his day to answer some questions about Hybrid Machining.

How did you get into manufacturing?  

I started working in an architectural shop during my high school years.  I quickly realized that there was a more advanced part of the industry that I was missing out on. Therefore, I started researching CNC Routing.  I fell in love with the technology and have been studying it ever since. 

What sort of machines and materials do you use in your shop?

We currently run a Datron Neo, Fanuc Robodrill, and a CR Onsrud 5-axis Router. We work primarily with wood, plastic, and non-ferrous materials. We currently use Autodesk Fusion 360, FeatureCAM, Powermill, Vectric Aspire, and AlphaCAM for CAM.  For CAD, we run Fusion 360, Inventor, and Solidworks.

hybrid machining datron neo

When did you start using 3D printing and how has it benefitted you?

I have been 3D printing for just over a year.  It was the first technology that we initiated here at Hybrid Machining, and it has allowed us to provide the best solution to the customer no matter what the requirements are. By expanding into 3D printing, we can help the customer decide which technology will work the best for their part. Many times, we take the “Hybrid” approach and use both additive and subtractive technologies together.

How have you adapted during the Covid-19 outbreak and how has it changed your business?

We started by stopping normal production to form a non-profit called 3DC19 with other local, small business owners with the sole purpose of 3D printing and assembling plastic face shields.  Hybrid Machining became the distribution center for the efforts.  Collectively, we produced and donated 75K articles of PPE to local hospitals, nursing homes, doctor offices, and first responders.  You can learn more about the efforts at www.3DC19.com. We have also been machining a lot of acrylic face guards for customers so that we can help them to get their office staff back to work safely. 

fanuc robodrill machine

What sets Hybrid Machining apart from the rest of the manufacturing community? 

We have a serious passion for educating our youth and local businesses on the rapid changes currently happening in the manufacturing industry and preparing them for the impact that Industry 4.0 will have on our lives in the future.  We want to produce knowledgeable people just as much as we produce products, and we do this in our unique Learning Lab.  We team up with local schools, vocational schools, and community colleges to help them spread the word about manufacturing.  We also intend to do ‘Lunch and Learns’ with local businesses to help them understand what other manufacturing methods and advanced materials are available on the market today.

What is the coolest project you have had come through the shop?

Many years ago, at my previous shop, we worked on the presidential handrail that the last three presidents stood behind during the inauguration.

hybrid machining metal business card

Are you using HEM techniques to improve cycle times? 

Yes, we use a couple of the fastest and most nimble machines on the market: the Datron NEO and the Fanuc Robodrill.  We leverage the machine’s tools’ high accelerations and deceleration rates, along with HEM, to drastically reduce cycle times for our customers.  This allows us to be competitive against over-seas importers.

What do you have to lose other than cycle time? You purchased the entire tool, not just the tip, so use it!  You will be surprised how the different the machine will sound and you can get parts done faster with less tool wear.

Why is high quality tool performance important to you?

The tooling is super important to the success of a project because the tool is what is doing the work.  I like to tell people, “Why would you buy a high-end sports car with all bells and whistles and then put crappy tires on it?  All that power and handling is worthless unless you have good tires.”  The same goes for tooling.  You can have a half-million-dollar machine that is super-fast and accurate and yet still produce a terrible part with cheap tooling. 

When was a time that Harvey Tool, Helical Solutions, or Micro 100 saved the day?

Harvey Tool helped me get through some tough composite projects in the past.  Their technical support team was extremely knowledgeable on the subject matter and helped me pick the right tool and parameters to get the job done. 

machined metal part from hybrid machining

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

NEVER STOP LEARNING.  Things may be going great at first and you think you have it all figured out, but then a new technology comes and swipes you off your feet.  Spend your spare time studying industry trends, talking to other business leaders, new and old, and preparing for the future.

 Is there anything else you would like to share with the “In The Loupe” community?

We are extremely thankful that Harvey Tool spends a lot of time developing ‘material-specific’ tooling.  We spend 90% of our time in that section of the catalog.  We recently tested out the new wood cutters and are extremely happy. We pushed these tools at speeds and feeds that are unbelievable.  We also use the Harvey Tool plastic cutters on a regular basis. 

Here at Hybrid Machining, we are blending the lines between routing and milling.  For many decades, the line had been fairly clear. There were certain types of jobs you ran on certain types of machines.  We are blurring those lines and are using the best tools for the jobs.  For instance, we use the 24K RPM spindle on the Robodrill to run it more like a router than a mill.  Therefore, we call it the “RoboRouter”.  We can produce wood and plastic parts at unbelievable speeds while achieving surface finishes that are off the charts.  This is not conventional practice, but the team at Hybrid Machining is willing to blaze the path forward for others to follow.

To check out more about Hybrid Machining go to their website or follow them on social media!

Achieving Success in CNC Woodworking

Developing a Successful Cutting Direction Strategy

There are a number of factors that can affect the machining practices of wood in woodworking. One that comes up a lot for certain hardwoods is the cutting direction, specifically in relation to the grain pattern of the wood. Wood is an anisotropic material. This means that different material properties are exhibited in different cutting directions. In terms of lumber, there are different structural grades of wood related to grain orientation. If the average direction of the cellulose fibers are parallel to the sides of the piece of lumber, then the grains are said to be straight. Any deviation from this parallel line and the board is considered to be “cross-grain”. Figure 1 below depicts a mostly straight grain board with arrows indicating the different axes. Each of these axes exhibits different sets of mechanical properties. Because of these differences, one must be conscious of the tool path in woodworking and minimize the amount of cutting forces placed on the cutter in order to maximize its tool life.

straight grain wood board with woodworking axes
Figure 1: Mostly straight grain board with arrows indicating different axes

Cutting perpendicular to the grain is known as cutting “across the grain” in woodworking. In Figure 1 above, this would be considered cutting in the radial or tangential direction. Cutting parallel to the grain is known as cutting “along the grain” (longitudinally in terms of Figure 1). The closer you are to cutting at 90° to the grain of the wood in any direction, the larger the cutting force will be. For example, a tool with its center axis parallel to the tangential direction and a tool path along the longitudinal direction would have less wear than a tool with the same center axis but moving in the radial direction. The second type of tool orientation is cutting across more grain boundaries and therefore yields greater cutting forces. However, you must be careful when cutting along the grain as this can cause tear-outs and lead to a poor surface finish.

The Proper Formation of Wood Chips With CNC Woodworking

When cutting wood parallel to the grain, there are three basic types of chips that are formed. When cutting perpendicular to the grain, the chip types generally fall into these same 3 categories, but with much more variability due to the wide range in wood properties with respect to the grain direction.

Type 1 Chips

Type 1 chips are formed when wood splits ahead of the cutting edge through cleavage until failure in bending occurs as a cantilever beam. A large force perpendicular to the shear plane is produced, causing the wood ahead of the cutting edge to split, forming this tiny cantilever beam. When the upward force finally exceeds the strength of this tiny beam, it breaks off.  These types of chips cause comparatively little wear compared to types 2 and 3, as the material is splitting before coming in contact with the pointed edge. End mills with either extremely high rake or very low rake angles often produce type 1 chips. This is especially true when machining against grain slopes that are greater than 25°. Woods with moisture content less than 8%form discontinuous chips and are at a higher risk of tear-out.

Type 2 Chips

Type 2 chips are the most desirable of the three types in terms of surface finish. They are a result of material failure along a diagonal shear plane, extending from the cutting edge to the workpiece surface. Type 2 chips form when there is a proper balance between the properties of the wood, cutting parameters, and cutter geometry. Woods with a moisture content between 8% and 20%have a much higher chance of forming continuous type 2 chips while leaving a good surface finish.

Type 3 Chips

The last type of chip forms when the rake angle of a cutter is much too low. In this scenario, the cutting force is almost parallel to the direction of travel. This causes a soft material, such as wood, to be crushed rather than sheared away, leaving a poor surface finish. Generally, the surface left behind looks like tiny bundles of wood elements, a surface defect commonly known as “fuzzy grain.” This type of chip occurs more frequently in softwoods as the crushing situation is compounded in low-density woods.

types of wood chips in woodworking
Figure 2: Different types of wooden chips

Extending Tool Life When Woodworking

Speeds & Feeds Rules of Thumb

There are several different categories of tool wear that occur when cnc woodworking. General rules of machining still apply as RPM has the greatest influence on wear rate. Over-feeding can increase tool wear exponentially and also cause tool breakage. As with most machining operations, a balance between these two is essential. If you are looking to increase your productivity by increasing your speed, you must increase your feed proportionally in order to maintain a balance that keeps the tool properly engaged in the material.

Proper Management of Heat

When cutting tools are exposed to high heat, they begin to wear even faster, due to corrosion. The cobalt binder within most carbide tools on the market begins to oxidize and break free of the cutting edge. This sets off a chain reaction, as when the binder is removed, the tungsten carbide breaks away, too. Different species of wood and types of engineered wood have different corrosive behaviors at high temperatures. This is the most consistent type of wear that is observed when machining MDF or particleboard. The wear is due to the chlorine and sulfate salts found in adhesives as this accelerates high-temperature corrosion.  As with aluminum, when the silica content of a wood increases, so too does its corrosiveness.

Generally, increased tool wear is observed in wood with high moisture content. This trait is due to the increased electro-chemical wear caused by the extractives in wood., Moisture content in wood includes substances such as resins, sugars, oils, starches, alkaloids, and tannins in the presence of water. These molecules react with the metallic constitutes of the cutting tool and can dull the cutting edge. Carbide is more resistant to this type of wear compared to high-speed steel.

Best Coatings for Extended Tool Life in Wood

If you want a longer-lasting tool that will maintain its sharp cutting edge (and who doesn’t), you may want to consider an Amorphous Diamond coating. This is an extremely abrasive resistant coating meant for non-ferrous operations in which the temperature of the cutting zone does not exceed 750 °F. This coating type is one of Harvey Tool’s thinnest coatings, therefore minimizing the risk of any edge rounding and maximizing this edge’s durability.

Avoiding Common Woodworking Mishaps

Tear Out

Tear out, sometimes called chipped grain or splintering, is when a chunk of the wood material being machined tears away from the main workpiece and leaves an unappealing defect where it used to be. This is one of the most common defects when machining wood products. There are many different reasons that tear out occurs. Material characteristics are something to be considered. Tear out is more likely to occur if the grain orientation is less than 20°relative to the tool path, the moisture content of the wood is too low, or the density of the wood is too low. Figure 4 shows the grain orientation angle relative to the tool path. In terms of machining parameters, it can also occur if either the chip load, depth of cut, or rake angle is too high.

woodworking grain in relation to tool path
Figure 4: Example of grain orientation angle relative to the tool path

Fuzzy Grain Finish

Fuzzy grain looks like small clumps of wood attached to the newly machined face and occurs when the wood fibers are not severed properly. Low rake or dull cutting tools indent fibers until they tear out from their natural pattern inside, causing type 3 chips to form, resulting in a poor finish. This can be exacerbated by a low feed or depth of cut as the tool is not properly engaged and is plowing material rather than shearing it properly. Softer woods with smaller and lesser amounts of grains are more susceptible to this type of defect. Juvenile wood is known to be particularly liable for fuzzy grain because of its high moisture content.

fuzzy grain wood finish
Figure 5: Example of a fuzzy grain finish

Burn Marks

Burn Marks are a defect that is particularly significant in the case of machining wood, as it is not generally a concern when machining other materials. Dwelling in a spot for too long, not engaging enough of the end mill in a cut, or using dull tools creates an excessive amount of heat through friction, which leaves burn marks. Some woods (such as maple or cherry) are more susceptible to burn marks, therefore tool paths for these types should be programmed sensibly. If you are having a lot of trouble with burn marks in a particular operation, you may want to try spraying the end mill with a commercial lubricant or paste wax. Be careful not to use too much as the excess moisture can cause warping. Increasing your tool engagement or decreasing RPM may also combat burn marks.

burn marks from wood cutter
Figure 6: Example of burn marks

Chip Marks

Chip marks are shallow compressions in the surface of the wood that have been sprayed or pressed into the surface. These defects can swell with an increase in moisture content, worsening the finish even more. This type of blemish is generally caused by poor chip evacuation and can usually be fixed by applying air blast coolant to the cutting region during the operation.

Raised Grain

Raised grain, another common defect of woods, is when one or more portions of the workpiece are slightly lower than the rest. This blemish is particularly a problem when machining softer woods with dull tools as the fibers will tear and deform rather than be cleanly sheared away. This effect is intensified when machining with slow feeds and the wood has a high moisture content. Variations in swelling and shrinking between damaged and undamaged sections of wood exacerbate this flaw. It’s for this reason that raised grain is a common sight on weather-beaten woods. Work holding devices that are set too tight also have a chance of causing raised grain.

Differentiating Harvey Tool Wood Cutting & Plastic Cutting End Mills

Machinists oftentimes use Plastic Cutting End Mills for woodworking, as this tool has very similar internal geometries to that of an End Mill for Wood. Both tools have large flute valleys and sharp cutting edges, advantageous for the machining of both plastic and wood. The main difference between the Harvey Tool plastic cutters and the woodcutters is the wedge angle (a combination of the primary relief and rake angle). The woodcutter line has a lower rake but still has a high relief angle to maintain the sharpness of the cutting edge. The lower rake is designed to not be as “grabby” as the plastic cutters can be when woodworking. It was meant to shear wood and leave a quality surface finish by not causing tear-out.

Harvey Tool’s offering of End Mills for Wood includes both upcut and downcut options. The upcut option is designed for milling natural and engineered woods, featuring a 2-flute style and a wedge angle engineered for shearing wood fiber materials without causing tear out or leaving a fuzzy grain finish. The downcut offering is optimized for milling natural and engineered woods and helps prevent lifting on vacuum tables.

For more help on achieving a successful machining operation, or more information on Harvey Tool’s offering of End Mills for Wood, please contact Harvey Tool’s team of engineers at 800-645-5609.