End mill selection

Joe P.

Joe P.

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I know there are many variables and considerations to take into account, but... are the any general guide lines in choosing what type of end mill to use. For instance number of flutes, coated vs. uncoated, helix, etc. Looking at the selection of end mills in catalogs and on websites can be very intimidating.


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Let me start by saying I'm no expert, so start with that. For hobby work I use high speed steel cutters usually 4 flute, for most jobs except slotting, where 2 flute are better due to chip removal. If the material being cut is stainless or work hardening I Use carbide. I haven't seen that much difference with the few TIN coated cutters I have used, but I'm not in a production environment either. I also use 2 flues on aluminum Jack
 
I would also stick with HSS unless you have a high speed mill, in which case inserted carbide might work for you. There are no hard rules to choosing end mills but there are some soft ones.
  • It is always a good idea to use a roughing end mill when possible to do the bulk of the work, then use a sharp end mill to finish. If your mill is on the small side, fine [pitch roughing] end mills work well.
  • There are centercutting and non-centercutting end mills; both are useful. You can plunge with both but the latter requires a drilled hole first.
  • There are single and double-ended end mills. They're the same; just flip the latter over when one end is dull.
  • 2 flute end mills give you the best chip clearance and are a good choice for general milling.
  • 3 flutes are good for slotting and also work well for general use.
  • 4 flutes or more are good for reducing chip load or when a fine finish is needed.
  • High helix end mills work great in aluminum; this applies to roughing and finishing end mills.
  • If you have to go deep, carbide deflects less but they like speed and they cost money.
  • Use the largest end mill you can for the job.
  • Learn the difference between conventional and climb milling - it matters to the mill, the end mill, the work and you.
There are many specialty end mills - corner rounding, ball, etc. I'll let others discuss those. The above is just general guidelines and I hope it makes it easier to choose.
 
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Thanks guys, this helps a lot.


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Here's my list.

1. Don't buy the cheap Chinese end mill sets. When starting out you don't need all the different sizes, I tended to only use the 1/2" and 3/8" ones in the set. They are also made out of suspect steel, just buy a few sizes of HHS to get started on.

2. Spend a little more and buy decent quality end mills. Worth it in the end.

3. My favorite end mill is a 1/2" carbide 4 flute that I got used in a larger lot of tooling. It cost very little and performs great. The seller told me it was a "combo" roughing and finishing end mill. All I know is it works.

4. Buy other sizes as needed based on the project you are working on unless you see a great sale or used tooling in the ads. I have some small HHS end mills (1/8" and 3/16") that I bought for a job that ended up being very useful for other projects. Didn't expect that at the time I bought them.
 
Unlike @sanddan, I keep several sets of the cheap import endmill sets around just for utility uses. I do agree that the quality is not consistent and some are pretty much junk, but they are cheap. I normally pick them up at Harbor Freight with the 25% off coupon. If you break one or burn it up you are not out much.

I also keep a variety of solid carbide and carbide tipped router bits around and use them for milling everything from wood to stainless steel. 1/2 inch shank is recommended where possible. Available at your local hardware store on a Saturday afternoon.;)

Don't worry too much about the coatings, for the home shop you are not concerned about getting maximum performance out of your machine and tooling. A bright finish is fine.

If I'm working on projects that requires good finishes and consistent quality, I buy high quality endmills specific to the job. If I think I need one end mill, I buy 3. That way when you break one, you have a backup(s), and if you don't use it for the job, then you have it for the next job. When buying job specific endmills, use aluminum cutting for aluminum, normally 2 or 3 flute, the geometry is a bit different than endmills designed for harder materials. For steel, normally 4 flute. There are exceptions, for example a 2 or 3 flute is best for cutting slots. Where possible use roughing endmills for maximum material removal.

The best way to insure that you do break an end mill is to buy only one. Normally buying at least 2 is the best way to insure that the first one doesn't break.:grin:
 
I think a followup question should be about coolant or cutting oil. I've found (I'm by no means an expert) that I've gotten the best results using flood coolant. Flood is a real mess, now I use Kool Mist in a 1 quart pressured spray bottle. I bought the bottle at WallyWorld in the garden department for $6 and change. It works almost as good as a full flood but with a lot less mess.
Mike
 
Damn. Where was this thread yesterday? I JUST researched all this information.

I only have one thing to add from my reading, if you decide to spend some extra and get a fancy coating, one of the common coatings on the high end ones I'd seen had aluminum in it. I read the the coating will react with any aluminum you try to mill with it and gum up/dull the cutter.

I can't wait to get mine in the mail!

Edit: Also, in school they said if you use carbide tooling, you either want to use no coolant, or flood coolant.
 
Hidyn said:
I read the the coating will react with any aluminum you try to mill with it and gum up/dull the cutter.
Click to expand...


Yup, ATiN, don't want to use that on aluminum.
 
Joe: You can get a good starter set by buying one of those "estate sale" endmill collections on Ebay. I got a good selection for 30$, even got a few brand new ones in the bunch, and if I break one it's no big deal. I also have a few of the cheap chinese ones and they do ok, but they're brittle; easy to snap.
Mark S.
 
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