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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.

Low Lead Angle

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)

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.”

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…)

Curvature of Bottom Edge

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.

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 the competitors?

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!

Schon DSGN – Featured Customer

In 2012, engineer Ian Schon wanted to put his skill for design to the test. He decided to challenge himself by designing a normal, everyday item: a pen. His goal was to take the pen from the design concept to manufacturing it within his own shop. Ian designed his pen how he thought a pen should be: durable, reliable, compact, leak-proof, and easy to use. Most of all, though, he wanted the pen to be of a superior quality, not something easily lost or thrown away.

With the design concept in place, Ian started his work on engineering and manufacturing his new pen. He made many prototypes, and with each discovered new features and additions to better his design. Today, Ian manufacturers his pens through local fabrications in Massachusetts, using local supplies. He makes them from 6061 Aluminum, unique in that it molds to its users’ hand, over time. His pens are designed to outlast its user and be passed on through generations.

Ian was kind enough to take time out of his busy schedule to answer some questions about his manufacturing success.

Schon DSGN silver wrist watch with black band

What sets Schon DSGN apart from competition?

I think I have a unique approach to designing and manufacturing. I design things that I like, and make them the way that I want to.  I don’t rush things out the door. I’m not thinking about scale, growth, making a big shop, etc. I just want to live a simple life where I make cool objects, sell them, and have enough time in the week to sneak out into the woods and ride my bike. This ethos takes the pressure off a lot, and that makes the workflow freer without as much stress as I had in my past career as a product development engineer.

This workflow isn’t for everyone. it’s not a winning combo for massive business success, per se, and if you audited me you would tell me I’m holding back by not scaling and hiring, but I like it. I see myself as a hybrid between artist and entrepreneur. I love doing things start to finish, blank paper to finished part on the machine. Owning that entire workflow allows for harmony of engineering, machining, tooling, finishing, R+D, marketing, etc. Further, it ensures that I don’t miss critical inflection points in the process that are ripe for process evolution and innovation, resulting in a better product in the end.

I’m sure the way I do things will change over time, but for now I’m still figuring things out and since I work largely alone (I have one amazing helper right now assisting with assembly, finishing, and shipping) I have lots of flexibility to change things and not get stuck in my ways.

Also, by working alone, I control the music. Key!

schon dsgn turning metal on lathe

Where did your passion for pens come from?

My friend Mike had a cool pen he got from a local shop and I was like “man I like that,” so I made one with some “improvements.” At the time, in my mind, they were improvements, but I have learned now that they were preferences, really. I made a crappy pen on a lathe at the MIT MITERS shop back in 2010, and that summer I bought a Clausing lathe on craigslist for $300 and some tooling and started figuring it all out. I made a bunch of pens, wrote with them, kept evolving them, and eventually people asked me to make pens for them.  I didn’t really intend to start a business or anything, I just wanted to make cool stuff and use it. Bottle openers, knives, bike frames, etc. I made lots of stuff. Pens just stuck with me and I kept pushing on it as a project for my design portfolio. Eventually it became something bigger. Turns out my pen preferences were shared with other people.

Schon dsgn gold and copper metal pens

What is the most difficult product you have had to make and why?

Making watch cases – wow. What an awful part to try and make on a desktop Taig 3 axis mill and a Hardinge lathe in my apartment! I started working on machining watch cases in 2012, and I finished my first one in my apartment in 2015 (to be fair, I was working on lots of other stuff during that time! But yeah, years…). What a journey. Taught me a lot. Biting off more than you can chew is a great way to learn something. 

What is the most interesting product you’ve made?

When I worked at Essential Design in Boston I worked on the front end of a Mass Spectrometer. The requirements on the device were wild. We had high voltage, chemical resistance, crazy tolerances, mechanism design, machining, injection molding – truly a little bit of everything! It was a fun challenge that I was fortunate to be a part of. Biomolecule nanoscale analysis device. Try saying that ten times fast.

I have something fountain pen related in the works now that I find more interesting, and very, very complex, but it’s under wraps a bit longer. Stay tuned. 

Schon dsgn gold and copper metal pens

Who is the most famous contact that you have worked on a project with?

I have made watches for some incredible customers, but I unfortunately cannot talk about who they are. Most of my watch work outside of my own parts is also under NDA which is a bummer, but hey it was great work regardless.

Same thing with the pens. I know that some of my pen are in the touring cases of a few musicians, one of which is in the rock and roll hall of fame. But I have to keep it tight!

Before leaving to work for myself, I was part of a design team at IDEO in Cambridge that designed the new Simplisafe Home Security System. As an engineer and designer, I got listed on the patents. That wasn’t machining and was more design and engineering of injection molded plastic assemblies,  but it was still cool, though! Cutting my teeth in the design industry before machining helps me a lot with the creative process in the workshop. Lots of overlap.

What capabilities does your shop have?

I utilize Citizen L series sliding headstock machines to run my company. These are Swiss Machines (though made in Japan) with twin spindles and have live tooling for milling operations. I got into this type of machining after getting advice from friends in the industry and subcontracting my work to shops with these style of machines for 7 years.

Beyond the Swiss Machines, I have a new Precision Matthews Manual Mill, a Southbend Model A, a Hardinge Cataract Lathe, and a bunch of smaller Derbyshire lathes and mills. Most of these are for maintenance related tasks – quick mods and fixtures and my watchmaking/R&D stuff. I also have a Bantam Tools Desktop CNC machine on the way, a nice machine for quick milled fixtures in aluminum and nonferrous materials. I tested this machine during their development phases and was really impressed.

What CAM/CAD software are you using?

I use Fusion 360 for quick milled stuff, but most of my parts are programmed by hand since the lathe programming for Swiss work can be done without much CAM. I’m sure I could be doing things better on the programming side, but hey, every day I learn something new. Who knows what I’ll be doing a year or two from now?

schon dsgn turning wrist watch on lathe

What is your favorite material to work with and why?

Brass and Copper. The chips aren’t stringy, it’s easy to cut quickly and the parts have this nice hefty feel to them. Since I make pens, the weight is a big piece of the feeling of a pen. The only downside is I’m constantly figuring out ways to not dent the parts as they are coming off the machines! My brass parts are like tiny brass mallets and they LOVE to get dinged up in the ejection cycles. I ended up making custom parts catchers and modifying the chutes on the machines to navigate this. I might have some conveyors in my future….yeah. Too many projects!

schon dsgn disassembled wrist watch

Why is high quality tool performance important to you?

It’s not just important, it’s SUPER important. As a solo machinist running my own machines, being able to call a tooling company and get answers on how I should run a tool, adjust its RPM, feed, DOC, or cutting strategy to get a better result is invaluable. I find that as much as I’m paying for tool performance, I’m also paying for expertise, wisdom and answers. Knowing everything is cool and all (and I know some of you out there know everything under the sun), but since I don’t know everything, it’s so nice to be able to pick up a phone and have someone in my corner. These tech support people are so crucial. Being humble and letting support guide me through my tooling challenges has helped me grow a lot. It’s like having a staff of experienced machinists working at my company, for free! Can’t beat that. Micro 100 and Helical have helped me tons with their great support.

schon dsgn multicolored fountain pens

When was a time that Harvey, Helical or Micro product really came through and helped your business?

The Helical team (shout out to Dalton) helped me nail some machining on some very wild faceted pens I was working on this month. When I switched to Helical, my finishes got crazy good. I just listened to recommendations, bought a bunch of stuff, and kept trying what Dalton told me to. Eventually, that led to a good recipe and manageable tool wear. It was great!

I also like how representatives from the Harvey/Helical/Micro family often cross reference each other and help me find the right solution, regardless of which company I’m getting it from. Nice system.

The quiet hero in my shop is my Micro 100 quick change system. It just works great. Fast to swap tools, easy to setup, cannot argue with it! Too good. 

Schon DSGN silver wrist watch with black band

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

Find a mentor who supports you and challenges you. Find a good tooling company, or good tooling companies, and make good relationships with their tech support so you can get answers. Make good relationships with service technicians who can help you fix your machines. Be a good person. Don’t let yourself become a hot head under the pressure of this industry (since it can be hard at times!), cooler heads prevail, always. Be open to seeing things from other viewpoints (in life and in machining), don’t be afraid to flip a part around and start over from square one.

To learn more about Ian and Schon DSGN, follow them @schon_dsgn and @the_schon on Instagram and check out his website. And, to learn more about how Ian got his start in the manufacturing industry, check out this video.

New Dublin Ship Fittings – Featured Customer

New Dublin Ship Fittings was established in 2017 by Lucas Gilbert, and is located on the scenic south shore of Nova Scotia, Canada.  Lucas began his career with a formal education in machining and mechanical engineering. In the early 2000’s, Lucas got into the traditional shipbuilding industry made famous in the region he grew up in, Lunenburg County, Nova Scotia. It is then when Lucas identified the need for quality marine hardware and began making fittings in his free time. After some time, Lucas was able to start New Dublin Ship Fittings and pursue his lifelong dream of opening a machine shop and producing custom yacht hardware.

Lucas was our grand prize winner in the #MadeWithMicro100 Video Contest! He received the $1,000 Amazon gift card, a Micro-Quik™ Quick Change System with some tooling, and a chance to be In the Loupe’s Featured Customer for February. Lucas was able to take some time out of his busy schedule to discuss his shop, how he got started in machining, and the unique products he manufactures.

How did you start New Dublin Ship Fittings?

I went to school for machine shop and then mechanical engineering, only to end up working as a boat builder for 15 years. It was during my time as a boat builder that I started making hardware in my free time for projects we were working on. Eventually, that grew into full-time work. Right now, we manufacture custom silicon bronze and stainless fittings only. Eventually, we will move into a bronze hardware product line.

New Dublin Ship Fittings shop

Where did your passion for marine hardware come from?

I’ve always loved metalworking. I grew up playing in my father’s knife shop, so when I got into wooden boats, it was only a matter of time before I started making small bits of hardware. Before hardware, I would play around making woodworking tools such as chisels, hand planes, spokeshaves, etc.

What can be found in your shop?

The shop has a 13”x 30” and 16”x 60” manual lathe, a Bridgeport Milling Machine, Burgmaster Turret Drill Press, Gang Drill, Bandsaw, 30-ton hydraulic press, #2 Hossfeld Bender, GTAW, and GMAW Welding Machines, as well as a full foundry set up with 90 pounds of bronze pour capacity. We generally only work in 655 silicon bronze and 316 stainless steel.

cnc machined boat parts

What projects have you worked on at New Dublin Ship Fittings that stand out to you?

I’ve been lucky to work on several amazing projects over the years. Two that stand out are a 48’ Motorsailer Ketch built by Tern Boatworks, as well as the 63’ Fusion Schooner Farfarer, built by Covey Island Boatworks. Both boats we built most of the bronze deck hardware for.

I’ve made many interesting fittings over the years. I prefer to work with bronze, so I generally have the most fun working on those. I’m generally the most interested when the part is very
challenging to make and custom work parts are often very challenging. I’m asked to build or machine a component that was originally built in a factory and is difficult to reproduce with limited machinery and tooling, but I enjoy figuring out how to make it work. cnc milled boat cleat

Why is high-quality tooling important to you?

When I first started I would buy cheaper tooling to “get by” but the longer I did it, the more I realized that cheaper tooling doesn’t pay off. If you want to do quality work in a timely fashion, you need to invest in good tooling.

What Micro 100 Tools are you currently using?

Currently, we just have the Micro 100 brazed on tooling but we have been trying to move more into inserts so we are going to try out Micro’s indexable tooling line. After receiving the Micro-Quik™ Quick Change System, we are looking forward to trying out more of what (Micro 100) has to offer. This new system should help us reduce tool change time, saving us some money in the long run.

cnc machined rigging

What makes New Dublin Ship Fittings stand out from the competition?

I think the real value I can offer boat builders and owners over a standard job shop is my experience with building boats. I understand how the fitting will be used and can offer suggestions as to how to improve the design.

If you could give one piece of advice to a new machinist what would it be?

The advice I would give to new machinists is to start slow and learn the machines and techniques before you try to make parts quickly. There is a lot of pressure in shops to make parts as fast as possible, but you’ll never be as fast as you can be if you don’t learn the processes properly first. Also, learn to sharpen drill bits well!

5 Things to Know About Helical’s High Feed End Mills

Helical Solutions‘ High Feed End Mills provide many opportunities for machinists, and feature a special end profile to increase machining efficiencies. A High Feed End Mill is a High Efficiency Milling (HEM) style tool with specialized end geometry that utilizes chip thinning, allowing for drastically increased feed rates in certain applications. While standard end mills have square, corner radius, or ball profiles, this Helical tool has a specialized, very specific design that takes advantage of chip thinning, resulting in a tool that can be pushed harder than a traditional end mill.

Below are 5 things that all machinists should know about this exciting Helical Solutions product offering.

1. They excel in applications with light axial depths of cut

A High Feed End Mill is designed to take a large radial depth of cut (65% to 100% of the cutter diameter) with a small axial depth of cut (2.5% to 5% diameter) depending on the application. This makes them perfect for face milling, roughing, slotting, deep pocketing, and 3D milling. Where HEM toolpaths involve light radial depths of cut and heavy axial depths of cut, these utilize high radial depths of cut and smaller axial depths of cut.

2. This tool reduces radial cutting forces

The end profile of this tool is designed to direct cutting forces upward along the axis of the tool and into the spindle. This reduces radial cutting forces which cause deflection, allowing for longer reach tools while reducing chatter and other issues that may otherwise lead to tool failure. The reduction of radial cutting forces makes this tool excellent for use in machines with lower horsepower, and in thin wall machining applications.

3. High Feed End Mills are rigid tools

The design and short length of cut of these tools work in tandem with the end geometry to produce a tool with a strong core, further limiting deflection and allowing for tools with greater reach lengths.

4. They can reduce cycle times

In high RDOC, low ADOC applications, these tools can be pushed significantly faster than traditional end mills, saving time and money over the life of the tool.

5. High Feed End Mills are well suited for hard materials

The rigidity and strength of High Feed End Mills make them excellent in challenging to machine materials. Helical’s High Feed End Mills come coated with Tplus coating, which offers high hardness and extended tool life in high temp alloys and ferrous materials up to 45Rc.

In summary, these tools with specialized end geometry that utilizes chip thinning and light axial depths of cut to allow for significantly increased feed rates in face milling, slotting, roughing, deep pocket milling, and 3D milling applications. The end profile of a High Feed End Mill applies cutting forces back up into the spindle, reducing radial forces that lead to deflection in long reach applications. Combining this end geometry with a stubby length of cut results in a tool that is incredibly rigid and well suited for harder, difficult to machine materials.

Benefits & Drawbacks of High and Low Helix Angles

While many factors impact the outcome of a machining operation, one often overlooked factor is the cutting tool’s helix angle. The Helix angle of a tool is measured by the angle formed between the centerline of the tool and a straight line tangent along the cutting edge.

A higher helix angle, usually 40° or more, will wrap around the tool “faster,” while a “slower” helix angle is usually less than 40°.

When choosing a tool for a machining operation, machinists often consider the material, the tooling dimensions and the flute count. The helix angle must also be considered to contribute to efficient chip evacuation, better part finish, prolonged tool life, and reduced cycle times.

Helix Angles Rule of Thumb

One general rule of thumb is that as the helix angle increases, the length of engagement along the cutting edge will decrease. That said,
there are many benefits and drawbacks to slow and high helix angles that can impact any machining operation.

Slow Helix Tool <40°

Benefits

  • Enhanced Strength – A larger core creates a strong tool that can resist deflection, or the force that will bend a tool under pressure.
  • Reduced Lifting – A slow helix will decrease a part from lifting off of the worktable in settings that are less secure.
  • Larger Chip Evacuation – The slow helix allows the tool to create a large chip, great for hogging out material.

Drawbacks

  • Rough Finish – A slow helix end mill takes a large chip, but can sometimes struggle to evacuate the chip. This inefficiency can result in a sub-par part finish.
  • Slower Feed Rate – The increased radial force of a slow helix end mill requires running the end mill at a slower feed rate.

High Helix Tool >40°

Benefits

  • Lower Radial Force – The tool will run quieter and smoother due to better shearing action, and allow for less deflection and more stability in thin wall applications.
  • Efficient Chip Evacuation – As the helix angle increases, the length of cutting edge engagement will decrease, and the axial force will increase. This lifts chips out and away, resulting in efficient chip evacuation.
  • Improved Part Finish – With lower radial forces, high helix tools are able to cut through material much more easily with a better shearing action, leaving an improved surface finish.

Drawbacks

  • Weaker Cutting Teeth – With a higher helix, the teeth of a tool will be thinner, and therefore thinner.
  • Deflection Risk – The smaller teeth of the high helix tool will increase the risk of deflection, or the force that will bend a tool under pressure. This limits how fast you can push high helix tools.
  • Increased Risk of Tool Failure – If deflection isn’t properly managed, this can result in a poor finish quality and tool failure.

Helix Angle: An Important Decision

In summary, a machinist must consider many factors when choosing tools for each application. Among the material, the finish requirements, and acceptable run times, a machinist must also consider the helix angle of each tool being used. A slow helix end mill will allow for larger chip formation, increased tool strength and reduce lifting forces. However, it may not leave an excellent finish. A high helix end mill will allow for efficient chip evacuation and excellent part finish, but may be subject to increased deflection, which can lead to tool breakage if not properly managed.

Axis CNC Inc. – Featured Customer

Axis CNC Inc was founded in 2012 in Ware, Massachusetts, when Dan and Glenn Larzus, a father and son duo, decided to venture into the manufacturing industry. Axis CNC Inc has provided customers with the highest quality manufacturing, machining, and programming services since they’ve opened. They specialize in manufacturing medical equipment and have a passion for making snowmobile parts.

We sat down with Axis CNC Inc to discuss how they got started and what they have learned over there years in the manufacturing world. Watch our video below to see our full interview.

Show Us What You #MadeWithMicro100

Are you proud of the parts you #MadeWithMicro100? Show us with a video of the parts you are making, the Micro 100 Tool used, and the story behind how that part came to be, for a chance to win a $1,000 Amazon gift card grand prize!

With the recent addition of the Micro 100 brand to the Harvey Performance Company family, we want to know how you have been utilizing its expansive tooling offering. Has Micro 100’s Micro-Quik™ system helped you save time and money? Do you have a favorite tool that gets the job done for you every time? Has Micro 100 tooling saved you from a jam? We want to know! Send us a video on Instagram and show us what you #MadeWithMicro100!

How to Participate

Using #MadeWithMicro100 and @micro_100, tag your video of the Micro 100 tools machining your parts on Instagram or Facebook. Remember, don’t share anything that could get you in trouble! Proprietary parts and trade secrets should not be on display.

Official Contest Rules

Contest Dates:

  • The contest will run between December 5, 2019 to January 17, 2020. Submit as many entries as you’d like! Entries that are submitted before or after the contest period will not be considered for the top prizes (But we’d still like to see them!)

The Important Stuff:

  1. Take a video of your Micro 100 tool in action, clear and visible.
  2. Share your video on social media using #MadeWithMicro100 and tagging @Micro_100.
  3. Detail the story behind the project (tool number(s), operation, running parameters, etc.)

Prizes

All submissions will be considered for the $1,000 Amazon gift card grand prize. Of these entries, the most impressive (10) will be put up to popular vote. All entries put up to vote will be featured on our new customer testimonial page on our website with their name, social media account, and video displayed for everybody to see.

We’ll pick our favorites, but the final say is up to you. Public voting will begin on January 21, 2020, and a winner will be announced on January 28, 2020.

The top five entries will be sent Micro 100’s Micro-Quik™ tool change system with a few of our quick change tools. The top three entries will be offered a spot as a “Featured Customer” on our “In The Loupe” blog!

The Fine Print:

  • Please ensure that you have permission from both your employer and customer to post a video.
  • All entries must be the original work of the person identified in the entry.
  • No purchase necessary to enter or win. A purchase will not increase your chances of winning.
  • On January 28, 2020, the top 5 winners will be announced to the public. The Top 5 selected winners will receive a prize. The odds of being selected depend on the number of entries received. If a potential winner cannot be contacted within five (5) days after the date of first attempt, an alternative winner may be selected.
  • The potential winners will be notified via social media. Each potential winner must complete a release form granting Micro 100 full permission to publish the winner’s submitted video. If a potential winner cannot be contacted, or fails to submit the release form, the potential winner forfeits prize. Potential winners must continue to comply with all terms and conditions of these official contest rules, and winning is contingent upon fulfilling all requirements.
  • Participation in the contest constitutes entrants’ full and unconditional agreement to and acceptance of these official rules and decisions. Winning a prize is contingent upon being compliant with these official rules and fulfilling all other requirements.
  • The Micro 100 Video Contest is open to residents in US and Canada who are at least 18 years old at the time of entry.

Selecting the Right Chamfer Cutter Tip Geometry

A chamfer cutter, or a chamfer mill, can be found at any machine shop, assembly floor, or hobbyist’s garage. These cutters are simple tools that are used for chamfering or beveling any part in a wide variety of materials. There are many reasons to chamfer a part, ranging from fluid flow and safety, to part aesthetics.

Due to the diversity of needs, tooling manufacturers offer many different angles and sizes of chamfer cutters, and as well as different types of chamfer cutter tip geometries. Harvey Tool, for instance, offers 21 different angles per side, ranging from 15° to 80°, flute counts of 2 to 6, and shank diameters starting at 1/8” up to 1 inch.

After finding a tool with the exact angle they’re looking for, a customer may have to choose a certain chamfer cutter tip that would best suit their operation. Common types of chamfer cutter tips include pointed, flat end, and end cutting. The following three types of chamfer cutter tip styles, offered by Harvey Tool, each serve a unique purpose.

Three Types of Harvey Tool Chamfer Cutters

Type I: Pointed

This style of chamfer cutter is the only Harvey Tool option that comes to a sharp point. The pointed tip allows the cutter to perform in smaller grooves, slots, and holes, relative to the other two types. This style also allows for easier programming and touch-offs, since the point can be easily located. It’s due to its tip that this version of the cutter has the longest length of cut (with the tool coming to a finished point), compared to the flat end of the other types of chamfer cutters. With only a 2 flute option, this is the most straightforward version of a chamfer cutter offered by Harvey Tool.

Type I Chamfer Cutter overview

Type II: Flat End, Non-End Cutting

Type II chamfer cutters are very similar to the type I style, but feature an end that’s ground down to a flat, non-cutting tip. This flat “tip” removes the pointed part of the chamfer, which is the weakest part of the tool. Due to this change in tool geometry, this tool is given an additional measurement for how much longer the tool would be if it came to a point. This measurement is known as “distance to theoretical sharp corner,” which helps with the programming of the tool. The advantage of the flat end of the cutter now allows for multiple flutes to exist on the tapered profile of the chamfer cutter. With more flutes, this chamfer has improved tool life and finish. The flat, non-end cutting tip flat does limit its use in narrow slots, but another advantage is a lower profile angle with better angular velocity at the tip.

Type II Chamfer Cutter overview

Type III: Flat End, End Cutting

Type III chamfer cutters are an improved and more advanced version of the type II style. The type III boasts a flat end tip with 2 flutes meeting at the center, creating a center cutting-capable version of the type II cutter. The center cutting geometry of this cutter makes it possible to cut with its flat tip. This cutting allows the chamfer cutter to lightly cut into the top of a part to the bottom of it, rather than leave material behind when cutting a chamfer. There are many situations where blending of a tapered wall and floor is needed, and this is where these chamfer cutters shine. The tip diameter is also held to a tight tolerance, which significantly helps with programing it.

Type III Chamfer Cutter overview

In conclusion, there could be many suitable cutters for a single job, and there are many questions you must ask prior to picking your ideal tool. Choosing the right angle comes down to making sure that the angle on the chamfer cutter matches the angle on the part. One needs to be cautious of how the angles are called out, as well. Is the angle an “included angle” or “angle per side?” Is the angle called off of the vertical or horizontal? Next, the larger the shank diameter, the stronger the chamfer and the longer the length of cut, but now, interference with walls or fixtures need to be considered. Flute count comes down to material and finish. Softer materials tend to want less flutes for better chip evacuation, while more flutes will help with finish. After addressing each of these considerations, the correct style of chamfer for your job should be abundantly clear.

How Boring Bar Geometries Impact Cutting Operations

Boring is a turning operation that allows a machinist to make a pre-existing hole bigger through multiple iterations of internal boring. It has a number of advantages over traditional drilling methods:

  • The ability to cost-effectively produce a hole outside standard drill sizes
  • The creation of more precise holes, and therefore tighter tolerances
  • A greater finish quality
  • The opportunity to create multiple dimensions within the bore itself

boring bar dimension explanation

Solid carbide boring bars, such as those offered by Micro 100,  have a few standard dimensions that give the tool basic functionality in removing material from an internal bore. These include:

Minimum Bore Diameter (D1): The minimum diameter of a hole for the cutting end of the tool to completely fit inside without making contact at opposing sides

Maximum Bore Depth (L2): Maximum depth that the tool can reach inside a hole without contact from the shank portion

Shank Diameter (D2): Diameter of the portion of the tool in contact with the tool holder

Overall Length (L1): Total length of the tool

Centerline Offset (F): The distance between a tool’s tip and the shank’s centerline axis

Tool Selection

In order to minimize tool deflection and therefore risk of tool failure, it is important to choose a tool with a max bore depth that is only slightly larger than the length it is intended to cut. It is also beneficial to maximize the boring bar and shank diameter as this will increase the rigidity of the tool. This must be balanced with leaving enough room for chips to evacuate. This balance ultimately comes down to the material being bored. A harder material with a lower feed rate and depths of cut may not need as much space for chips to evacuate, but may require a larger and more rigid tool. Conversely, a softer material with more aggressive running parameters will need more room for chip evacuation, but may not require as rigid of a tool.

Geometries

In addition, they have a number of different geometric features in order to adequately handle the three types of forces acting upon the tool during this machining process. During a standard boring operation, the greatest of these forces is tangential, followed by feed (sometimes called axial), and finally radial. Tangential force acts perpendicular to the rake surface and pushes the tool away from the centerline. Feed force does not cause deflection, but pushes back on the tool and acts parallel to the centerline. Radial force pushes the tool towards the center of the bore.

boring bar geometry chart

Defining the Geometric Features of Boring Bars:

Nose Radius: the roundness of a tool’s cutting point

Side Clearance (Radial Clearance): The angle measuring the tilt of the nose relative to the axis parallel to the centerline of the tool

End Clearance (Axial Clearance): The angle measuring the tilt of the end face relative to the axis running perpendicular to the centerline of the tool

Side Rake Angle: The angle measuring the sideways tilt of the side face of the tool

Back Rake Angle: The angle measuring the degree to which the back face is tilted in relation to the centerline of the workpiece

Side Relief Angle: The angle measuring how far the bottom face is tilted away from the workpiece

End Relief Angle: The angle measuring the tilt of the end face relative to the line running perpendicular to the center axis of the tool

boring bar geometric features

Effects of Geometric Features on Cutting Operations:

Nose Radius: A large nose radius makes more contact with the workpiece, extending the life of the tool and the cutting edge as well as leaving a better finish. However, too large of a radius will lead to chatter as the tool is more exposed to tangential and radial cutting forces.

Another way this feature affects the cutting action is in determining how much of the cutting edge is struck by tangential force. The magnitude of this effect is largely dependent on the feed and depth of cut. Different combinations of depth of cuts and nose angles will result in either shorter or longer lengths of the cutting edge being exposed to the tangential force. The overall effect being the degree of edge wear. If only a small portion of the cutting edge is exposed to a large force it would be worn down faster than if a longer portion of the edge is succumb to the same force. This phenomenon also occurs with the increase and decrease of the end cutting edge angle.

End Cutting Edge Angle: The main purpose of the end cutting angle is for clearance when cutting in the positive Z direction (moving into the hole). This clearance allows the nose radius to be the main point of contact between the tool and the workpiece. Increasing the end cutting edge angle in the positive direction decreases the strength of the tip, but also decreases feed force. This is another situation where balance of tip strength and cutting force reduction must be found. It is also important to note that the angle may need to be changed depending on the type of boring one is performing.

Side Rake Angle: The nose angle is one geometric dimension that determines how much of the cutting edge is hit by tangential force but the side rake angle determines how much that force is redistributed into radial force. A positive rake angle means a lower tangential cutting force as allows for a greater amount of shearing action. However, this angle cannot be too great as it compromises cutting edge integrity by leaving less material for the nose angle and side relief angle.

Back Rake Angle: Sometimes called the top rake angle, the back rake angle for solid carbide boring bars is ground to help control the flow of chips cut on the end portion of the tool. This feature cannot have too sharp of a positive angle as it decreases the tools strength.

Side and End Relief Angles: Like the end cutting edge angle, the main purpose of the side and end relief angles are to provide clearance so that the tools non-cutting portion doesn’t rub against the workpiece. If the angles are too small then there is a risk of abrasion between the tool and the workpiece. This friction leads to increased tool wear, vibration and poor surface finish. The angle measurements will generally be between 0° and 20°.

Boring Bar Geometries Summarized

Boring bars have a few overall dimensions that allow for the boring of a hole without running the tool holder into the workpiece, or breaking the tool instantly upon contact. Solid carbide boring bars have a variety of angles that are combined differently to distribute the 3 types of cutting forces in order to take full advantage of the tool. Maximizing tool performance requires the combination of choosing the right tool along with the appropriate feed rate, depth of cut and RPM. These factors are dependent on the size of the hole, amount of material that needs to be removed, and mechanical properties of the workpiece.