How do you pick the best end mill for the job when there are hundreds to choose from?
Let’s start with the basics and work our way down the list.
HSS vs. Carbide End Mills
Carbide has come a long way. For the price, high speed steel is usually not worth considering anymore. You now get at least 3 times the performance from a carbide end mill and 2 – 5 times the lifespan of HSS.
High Performance vs. General Purpose End Mills
You should now define your specific needs before you shop for an end mill. Your needs should dictate how much you end up spending. For example, if you only have a few parts to produce, or if lowering your cutting cycle time is not a priority, or if you have a very low tooling budget, you may be better off with a less expensive general purpose end mill.
General Purpose (GP) End Mills – Standard 2, 3, or 4 flute geometry end mills
- Least expensive style of end mill
- Can be used on a wide variety of materials
- Can often be resharpened locally
- Mills at slower speeds and feeds than HP end mills, thus longer cycle times
- May leave a mediocre surface finish or chatter easily
- Has a shorter life than an HP mill, and need changed more frequently
High Performance (HP) End Mills – Specialized geometries for specific material being cut
- When shorter cycle times are critical, the HP end mills can mill at higher speeds and feeds than GP tools
- Leaves a superior surface finish, often eliminating chatter by utilizing variable flute geometries
- Offers a longer tool life than GP end mills, meaning less tool changes
- In some cases, they can deliver ten times the performance of previously used GP tools
- Usually a more expensive style of tooling
- Can only be used to mill very specific materials
- Cannot usually be resharpened
2 Flute End Mills:
2 flute end mills are usually reserved for plunging applications or in some cases for side milling in materials that require deeper flute gullets to improve chip evacuation. They are used mostly in soft gummy materials like aluminum and plastics. 2 flute end mills smaller than 1/8 in diameter are considered “miniatures” and are more common in 2 flutes than 4 flutes in order to allow the flutes to deliver proper chip evacuation, even in steels.
3 Flute End Mills
3 flute end mills are usually used for a higher efficiency option than 2 flute end mills in aluminum & plastics. The extra flute allows for faster feed rates in these materials while still allowing sufficient chip evacuation, however 3 flute end mills cannot plunge efficiently like 2 flute end mills can.
4 Flute End Mills
4 flute end mills are generally for steels. A 4 flute general purpose carbide end mill can be used to cut any grade of steel. 4 flute high performance end mills are generally used for very specific grades of steel.
5 Flute End Mills
End mills with 5 flutes and higher are most often high performance end mills with a very specific milling application and usually for a specific grade of steel.
Length of Cut
Choosing length of cut (LOC) again depends on your needs. If your tooling budget is low and cycle time is not critical, you may opt for a longer length of cut in order to use the same tool on a variety of jobs in the future, but be careful, this could make your current job more difficult to mill efficiently.
The safest choice is to choose the shortest LOC needed to complete your current job. The shorter the LOC, the more rigid the end mill is and faster it will cut, yielding the best results and surface finish. You may end up accumulating more end mills this way but you will avoid many headaches during the actual milling process. A large collection of tooling is an investment in your future machining efficiency.
Always verify which coating is suitable for the material you are cutting. Coatings generally can add 15%-25% to your speeds, feeds, and tool life, providing you have picked the proper coating. The most common coatings used today are AlTiN and it’s many variations for use in steels. ZrN is currently the best choice for most aluminums. TiAlN, AlTiN, and uncoated tools can also be used for aluminums but TiAlN & AlTiN should only be used in aluminum if you are using flood coolant. Running these coatings dry in aluminum will cause aluminum buildup or galling. Using coolant will provide sufficient lubrication to prevent this from happening.
Who Should I Buy End Mills From?
Aren’t end mills all the same? They look similar, how much difference can there be? The answer is, a lot. Here are some of the determining factors.
There are over thirty geometry settings and angles that must be chosen by the programmer to create any given end mill, and they all work in harmony. Change one by just a few thousandths or a half degree and it changes the performance of the tool.
The grade, quality, and consistency of the carbide blank is crucial. Was it from a reputable carbide manufacturer, or was it the carbide blank that was the cheapest price this month?
The CNC Grinder
Is it old or a low end grinder without the newest programming software? Are they using the best diamond wheels? These things will affect how the end mill cuts for you.
Coolant and Filtration
Is the grinder’s filtration system up to snuff? It takes very expensive sub-micron filtration systems to consistently manufacture a high quality end mill. The less money spent on filtration, the lower the final quality, consistency and performance of the end mill.
All coating facilities are not the same. The coaters have control over their own coating “recipe” making it important that the tool manufacturer uses a reputable, consistent coater for their tools.
“But these are all things I won’t know about the manufacturer,” you say?
Correct, but bottom line is that you get what you pay for in the end mill market. It’s safest to stick with a manufacturer that has a good reputation among other machine shops and if the price is too good to be true, there is a reason. Choosing the right tool for the job will help yield the best milling experience and end result.
Thanks to Lakeshore Carbide for contributing to this article on selecting the right end mill! See more at http://www.lakeshorecarbide.com/
Lakeshore Carbide is a company devoted to manufacturing and distributing the highest quality USA made carbide end mills at the lowest prices possible. Before we place an end mill line on our site it must withstand aggressive testing. Our endmills continue to outperform our competitors in the machining of tool steels, stainless steels, carbon alloys and aluminum alloys. Our end mills achieve this due to the use of premium American carbide blanks held to an H6 tolerance, unique geometries, and high quality coatings. The end result is a high performance endmill that delivers solid reliability at a value price.