by Peter Jacobs, via OSG USA blog

​There are almost as many distinct variations of CNC tools as there are finished products that could be milled. If you are familiar with the functions these tools perform, it will be much more straightforward for you to select the ones appropriate for the project you are working on.

​When it comes to the amount of time it takes and the quality of the work to be produced, choosing the appropriate cutting tool for your CNC milling machine, the material, and the type of milling can have a significant impact.

So here is a list of prominent milling tools utilized for CNC cutting.

Different types of CNC milling tools make it feasible to achieve the highest level of product customization. While cutting into and shaping different types of materials, several tools are employed.

The tool that should be utilized to cut also gets decided by the finalized design of the cut. Aside from these factors, specialists choose their tools based on how well they match the required speed with the desired finish.

​Depending on the ultimate purpose of the completed product, one of these two considerations might take precedence over the other.

The top 7 milling tools for CNC cutting are: 

There are numerous kinds of end mills, each of which is designed for a particular kind of cutting. All end mills cut at an angle of ninety degrees. 

A center-cutting end mill is what's required to make a vertical cut. These mills can cut both the center and the margins of the workpiece.

Non-center cutting end mills feature a hole in the middle of the tool and only contain cutting edges mostly along the ends of the mill. Since roughing end mills have fewer flutes than standard end mills, they are the tools of choice for making the initial cuts in a workpiece.

You will need finishing end mills with additional flutes to obtain a design similar to the part you want to produce. It will enable you to deliver a component that is cut with immense precision.

The tool employed on a project will vary depending on several factors, the most important of which is the number of flutes and the material of its composition.

​The production of end mills typically involves the use of cobalt, high-speed steel, and carbide as raw materials. More details about the different types of mills (as per their material) are given below.

• Cobalt: Cobalt mills only contain eight percent cobalt, with the remaining construction built of steel.  Cobalt mills can run at a pace that is 10 percent quicker than their counterparts.
• Carbide: The use of carbide end mills is recommended for finishing procedures.
• High-Speed Steel (HSS): It is the go-to material for mills of all kinds. It strikes an optimal balance between tool cost and service life. Since HSS has sufficient flexibility, it can be utilized for cutting iron and other materials.

End mills may perform a wide variety of cuts, the type of tool used depends on the type of cut being made:

• Face Milling - It is the process of just cutting into one surface of a material.

• Side Milling - It is used when chamfer mills are being employed to create beveled edges. To penetrate and smooth off the corner, you move the mill along the material's edge.

• Ramping - Ramping is a way of cutting at an angle into a surface, usually a diagonal cut through the material. It produces an angled toolpath while concurrently milling in the radial and axial directions. Toolpaths for ramping can be either circular or linear.

• Plunge Milling - It causes the end mill to plunge vertically into the workpiece. Like ramping, plunge milling necessitates using a center-cutting end mill to clean out the material from the hole's inside and perimeter.

• Slot Milling - Slot milling creates slots using an end mill to carve a groove in a material while cutting the edges on both sides simultaneously.

This tool is primarily used to create a level surface on a solid portion of the material. As the first step in milling, this is often performed on the top of the stock to smooth it out. The cutter inserts in a face mill's sole body can be changed for specialized cutting tasks. You would require more cutters to remove metal at a faster rate.

Drill bits resemble end mills in that they have a conical cutting tip on the end of a shaft with one or even more flutes. Twist drills are often made from solid carbide or High-Speed Steel (HSS). The drill's hardness, wear resistance, and lifespan can be improved by applying a gold-colored coating, such as TiN.

Fly cutters are considered the best to create a fantastic surface finish.  The clockwise motion of these cutting tools produces a mirror-like finish on the material.

These stocky tools first construct a precise conical hole to avoid the drill bit from drifting during a cutting operation and end up drilling the hole at an incorrect site. Screw clearance holes and counterbores can be drilled with the same tool thanks to multi-function drills that spot and countersink.

Reamers are mainly utilized to enlarge the existing holes in compliance with the tolerance while providing a superior surface finish. They help you ensure the accuracy of the roundness and diameter of a drilled hole.

​For reamers to work, a pilot hole of roughly the same diameter as the final product must first be bored.

Taps are tools used to cut threads into the interior of a material. Yet not every thread is produced by a cutting procedure. By applying pressure, Roll Form taps get inserted into holes, and the surrounding material is shaped to fit them.
​
Thread mills are similar but can be employed to cut internal or external threads.

The key to successfully machining products and components is selecting the appropriate CNC tool. Learn how each one functions, and keep in mind the use of the most beneficial ones in your manufacturing facility.

Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general.

In the aerospace industry, aluminium structural parts, such as wing parts and frame elements are generally milled from solid material. A buy-to-fly ratio of 22 (95 %) is not uncommon here.

New machine generations that have sufficient drive power and the necessary spindle speeds make the high-performance machining of aluminum parts cost effective. MAPAL has developed a new range of aluminium roughing mills especially for these machines.

The OptiMill-SPM (structural part machining) high performance mill is equipped with a cutting edge that makes up 60%-80% of its diameter. This represents the maximum contact depth for the high-performance milling of aluminum.

Thanks to a highly positive cutting edge geometry and optimised chip flutes, the cutting force of PCD mills is reduced by up to 15%. Even when milling on standard machines, this reduction in cutting force results in more efficient machining parameters, and hence in improved performance.

​The bottleneck form of the mill prevents the tool from bending during the machining process. Another advantage of this stable design 
is the clearance that is created between the wall of the part and the mill shank. This prevents chips from scratching the wall of the part, particularly if it has deep pockets.

OptiMill-SPM tools with internal cooling are available in a solid carbide design with a diameter range of 6 to 32 mm or in a PCD design with a diameter range of 6 to 50 mm as part of the standard range. The range of products also includes variants with the well-known CFS replaceable head system.

Alpha Granite & Tile in Austin, TX, has grown steadily since its opening in 2003, adding and diversifying machinery, materials and service offerings along the way, eventually earning the title “Accredited Natural Stone Company” from the Natural Stone Institute. They’ve expanded to deliver a range of custom residential and commercial stone surfaces, from wall cladding to kitchen countertops, in more than 150 colors of granite, marble, onyx, quartz, quartzite and ultra-compact sintered surfaces.

To keep up, Alpha Granite has invested in several advanced CNC machines, diminishing or altogether eliminating many of the laborious and time-consuming processes. Despite the technological advances, there was still a bottleneck that frustrated owners Denis and Sonia Phocas.

“Measuring tools in the stone industry was always a very laborious process,” explained Denis Phocas. “It’s archaic. You get wet, dirty and it takes a really long time. In reality, the process destroys tools because employees know the time and effort involved, so they tend to skip the necessary measuring intervals [ultimately cutting tool life roughly in half].

Dressing of the tools is also skipped, as this process needs to be done after a set amount of linear feet of work. In essence, the tools need to be measured and sharpened at set intervals to increase life.”

The traditional measuring process is manual. Measuring height and diameter to set up and inspect tools requires handheld instruments like calipers. Phocas explains how important accurate and sharp tools are to cutting stone profiles.

Since each profile requires several passes by six or seven different tools, each dependent on the accuracy, and more delicate than the one before. In other words, if the first tool isn’t dialed in right, the profile shape will be deformed, tools wear faster and the hours spent preparing them are wasted.

“Finding the center of one tool is hard enough,” he said. “Finding the center in relation to six others is very difficult.”

Phocas had heard about tool presetters, essentially a powerful microscope with a high-resolution monitor and basic computing power. It allows for precise inspection and measurement of tool edges. The process is relatively new to the stone industry and mostly limited to larger fabricators. As he explored further, Phocas began to understand why — only the big guys could afford them.

​The presetters he saw from his distributers were big, expensive and, frankly, had more bells and whistles than a family-owned independent shop like Alpha Granite would need. Phocas recalled thinking, “It was such a major expense. Who needs to spend $60,000 on something you don’t need fully automated? There had to be a smaller solution.”

Phocas approached suppliers about entry-level options, but they continued pushing more expensive options. He got creative and found a metalworking supplier, Big Kaiser Precision Tooling in Hoffman Estates, IL, that might be able to help. The Speroni STP Essentia they offered featured a compact bench-top design, could work with any brand of router tools and handle the more complex tool profiles in stone cutting with ease. Most importantly, it was much less expensive than the other options he had found.

After working closely with a representative from Big Kaiser, even trying out an Essentia in his shop, Phocas was convinced and decided to purchase one. While there are significantly fewer types of tools used for profile cutting, this new capability and process would be an adjustment at first, starting with installation.

“I had never worked with one of these,” said Phocas. “It’s a precision tool. I wouldn’t call it daunting, but the process was interesting. We installed it in the workshop manager’s office because we wanted to keep it in a clean environment and because it’s got a computer hooked up to it. In the end, the installation process was pretty straightforward.”

by, Bernard Martin

As carbide end mills gain higher and higher speeds and metal removal rates there has also been a trend by round tool manufacturers to tighten up the tolerances on both the cutting diameter and the shank diameter to improve concentricity. At the same time, shrink fit holders have become more and more popular because they hold a tighter concentricity as well.  To achieve this both the shank and the bore now have similar surface finishes and this has led to a problem  The tools pull out in the cut.

Shrink fit holders are the most accurate for TIR as the toolholder engages completely around round shank tools with a bore tolerance of -0.0001" to  -0.0003".  As high performance end mills have tightened shank tolerances to the same range of -0.0001" to  -0.0003" they have used finer and finer grain grinding wheels which give the shanks a 'shiny' appearance. 

Shiny means that the superfinished shank has a lower coefficient of friction. So, although the TIR is tighter, the shank is more "slippery".   End mills traditionally had surface finish of about 8 μin on the tool shank. But that's changed.  It's been recommended that tool shanks used in shrink fit holders should not have a finish finer than 16 μin. for optimum holding power, but tell that to the guy who just superfinished the end mill to a super cocncentric tolerance that you don't want it looking that good.

Everyone knows that the last thing you want is for the end mill to slip in the middle of a heavy cut or on the finishing pass of a high tolerance part.  These 'hi performance' end mills, often times have higher helix angles which are great for ejecting chips but also create a higher pull out force on that slippery shank. And reducing the helix angle is not the answer.

We  already know that the gripping pressure is a function of the interference between the tool shank  and the shrink fit toolholder bore. Most shrink fit holders have a already bore surface finish of between 12 μin. and 16 μin.  So they are ground to a very high tolerance and have about the same surface finish as the toolholder shank.

End mill manufacturers and machinist have tried a variety of methods over the years to stop the tools from pulling out. This has ranged from grit blasting the shank to rubbing chalk on the shank, but most everyone in the industry has felt that the problem really needs to be addressed by the longer life toolholder rather than the replaceable cutting tool.

That's the problem that Techniks wanted to address. Techniks claims that their "proprietary non-slip TTG594 compound virtually fuses the tool shank with the shrink fit toolholder."

ShrinkLOCKED Toolholders eliminate cutting tool pull-out and provide 4X the friction drive force compared to un-treated shrink holders.

It’s not just a rougher bore finish that enhances the holding power. TTG-594 is a compound that has a much higher Brinell hardness than carbide so it can “bite” into the tool shank. But this does not affect the ability to perform tool changes.

Techniks arrived at their 4x the holding power comes from torsion testing vs. a standard shrink fit toolholder. They used a ¾” carbide gage pin in a standard holder and found the torque at which the tool will spin in the bore.

They then tested the ShrinkLOCKED holder using the same test.

According to Greg Webb, at Techniks,
"We actually could not find the point at which the tool would spin in the ShrinkLOCKED holder as we broke the carbide gage pins at 4x+ times the torque of the standard holder. The holding power is greater, we just have not found a way to measure this, so we kept our claims conservative at 4x."

With this innovative centering tool from Big Kaiser, spindles and tools can be centered quickly and easily.  It's ideal for limited spaces within small lathes.  The Centering Tool is a static dial gauge for easy centering.

• Reduce setup time
• Centering the tool holder is simplified since the dial gauge position is static and in front
• Easy setting with a fine adjustment mechanism
• Magnetic base allows for flexible mounting positions

Check out the technical video below to learn how to get center on your CNC Lathe.

Precision Cutting Tools already holds one of the highest tolerances on shank diameter in the industry for their end mills.  All PCT End Mills Shanks hold an h6 tolerance! That means that 
1/8" - 1/4": -0.0001"/-0.0003"
1/4" - 1/2": -0.0001"/-0.0003"
1/2' - 1": -0.0001"/-0.0004"

A tighter grind tolerance often times will mean a much shinier polished shank.  A polished shank is more apt to have lower coefficient of friction which makes it more prone to slip particularly while being held in a collet type toolholder.  

We are very excited to announce that we are now able to offer on-site technical training to YOUR machinists at YOUR location!  This is offered at no charge  to customers who use any of the manufacturer's whom we represent in California and Nevada.  

However, just because you don't purchase things from us, don't feel left out! We also offer on-site topic specter training on any of the following topics for $150/hour.  

Each presentation lasts about 2 hours.  The presentations last approximately 45-60 minutes with the remaining time for Q&A and discussion about unique applications in your facility.

Since the introduction of the XT Series 4 flute, 5 flute and the new 279 series 4 flute ball nose end mills they have proven to be a huge success in the machining of Titanium and stainless steels.   These tools have already made their impact in the machining of many other areas such as all steels and super alloys.
 
MA Ford's spotlight focus is on some other materials that are widely used in the market.  17-4 PH stainless many feel is somewhat difficult to machine and performance may vary depending on the material hardness.  That is not the case with the new XT series end mills.  These tools do not seem to care what hardness is presented to them!  28-42 RC is primary range for this series of stainless steel.  

Example: A customer had a very difficult 17-4 PH medical component with lots of contouring both roughing and finishing.  A 1/2" 279 Series was used for roughing the profile at 600 SFM with a depth of .015 and .025 step over at 80 IPM.  The customer had to double the speeds and feeds as well as increase the step over to get the desired finish required!

The 277 Series 4 flute can full slot up to 1X dia. depth at speeds as high as 260 to 340 SFM. The chip loads will be lighter than profile milling dependent on the tool diameter and fixture set up. The slotting depth can be increased even beyond 1X depth (which generally requires a reduction in speeds and feeds).
 
The 278 Series 5 flute can slot up to 1X depth effectively but slotting is more suited for the  4 flute 277 Series if a lot of slotting is to be done.  The speeds and feeds are the same as the 277, but calculations must be made for the additional cutting edge.  It is not recommended to slot over 1X the tool diameter with this 5 flute tools as it is best suited for profile milling both conventional and high speed machining.
 
The new 279 Series 4 flute ball nose end mill is an excellent choice for both conventional and high speed machining of stainless steels.  With the added radial relief and a thicker cross section in the center of the tools it can withstand extreme speeds and feeds both roughing and contouring.