End mills for Shapeoko newbie

Hi all,

My Shapeoko 3 is arriving in the next few days and I’m looking to purchase end mills for my projects. I’m new to CNC milling. I have 2 main needs:

  1. Cut out shapes out of 3 - 5mm plastic/acetate/celluloid . There will be some minor pocketing but mostly just cutting shapes. The material I plan to use is relatively expensive (for me!), so I would like wastage to be minimum. I was thinking of using a 2mm or even a 1mm diameter end mill for the cut-outs. Is this feasible and which type of end mill would you suggest?

  2. Cut out shapes out of 2mm brass sheet. Again, a little bit of pocketing but mostly just 2D shape cutting. Several repeat parts need to be cut. Which end mill (hopefully small diameter) would be most suited?

Thanks you very much for your input.

1/8" (3.17mm) and 1/4" (6mm) square end mills should be your go-to for getting started. Running less than 1/8" to start is probably more likely to just cause a lot of frustration. The endmill needs enough clearance in it to contain the chips and extract them and still not melt the material from running too slowly, a big problem with plastics. 1/4" will be a lot more forgiving than the 1/8". Both will work fine on both brass and plastic with the right speeds and feeds.


We have a bit written on this at: https://docs.carbide3d.com/support/#tooling-support and the community has more at: https://wiki.shapeoko.com/index.php/Endmills

I doubt the material is more expensive than an endmill, so concur w/ @mikep that you’ll want to start w/ 1/8" at least.

Thank you both! As I’m new to this, by 1/8" square end mill do you mean that’s the diameter of the shank or the cutting part? Also, how to decide on whether to purchase an upcut, down cut or compression bit?

1/8" square refers to the cutting part. Diameter is a separate consideration.

For plastics up cut or straight is usually best. Down cut or compression are only needed for wood and the latter for plywood.

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Great, thanks. So one of my designs has a 2mm hole through it. Would I then cut the shape with a 1/8 square end mill and then change to a 2mm bit for the hole? Apologies if this is a very basic question.

Yes, that would work, but you’d need an endmill smaller than 2mm — Carbide Create doesn’t support drilling so you need to cut as a pocket which must be larger than the endmill used.

Alternately you could use a V endmill to mark the hole and then finish up on a drill press.

See: https://docs.carbide3d.com/tutorials/tool-change/

You might want to also consider just drilling your hole with a hand drill/drill press. End mills make awful drills, and drills make awful end mills. You would need an end mill <<2mm to cut a 2mm hole to allow enough room for chip evacuation (ie. relative to the size of the endmill a pocket)

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Excellent, thank you both very much!

Mikep… so if I need to cut a 2mm slot/pocket right through the plastic, exactly what size end mill would I need? Is it 10% smaller than the desired width?

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It needs to be 10% smaller for CC to “fit” it in the hole. Part of the issue here is going to be cut length on small end mills - the flutes usually aren’t too long on the really small end mills, so be sure you find something with at least as much flute as the material you’re cutting.

For 2mm material, I’d say 1.5, 1.75 mm, but it’ll depend a bit on what you can find.

ALSO, keep in mind that you MAY need a different collet to match such a small endmill if it doesn’t match up with the collets with your router. I assume you’re in Europe, someone else can probably comment on a more local source of precision collets than Elaire (https://elairecorp.com/routercollets.html) or Precisebits (https://www.precisebits.com/products/equipment/dewalt_611_kits.asp).

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Mikeep - thanks every so much, that’s super helpful :slight_smile: Yes, I’m based in London. I’ve just ordered a 1/4" to 1/8" reducer collet for exactly this reason.

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