How are miniature endmills made?

William Ward · Jun 22, 2017

I know it's kind of a silly question, and I know they are ground from solid on a CNC cutter grinder. But I have been asked by more than one colleague how they are made and I don't have an answer I'm comfortable isn't 50% guess and 50% BS. I'm asking about the really small ones, under .010" diameter.

I regularly use a .005" diameter x .046" reach 2 flute from Richards Micro-Tool that I can barely see under the scope and it is amazing that something that small with that L/D ratio can be produced at all let alone produced and sold for what they sell for.

So how are they ground and what grit wheel is needed to keep the wheel edge sharp enough to produce the lips and make it center cutting?

Milland · Jun 22, 2017

CarbideBob would know better, but I think that some grinders use an opposed wheel setup, where both (usually it's two for really small EM's) flutes are ground together so there's minimal deflection. I'm sure there's a high loss rate, but no idea of the percentage.

What I'm really curious about is the relationship of carbide grain size and relative strength/stiffness. At some point a cutter becomes small enough that it's like boulders being held together with grout, and no longer what we're used to with "macro" tools. Would love to see some solid data on what the strength curve looks like with feature size.

ballen · Jun 22, 2017

I am told that Swiss grinding machines are the ones used to make the very smallest of these end mills and cutters. But I do not know the details.

Conrad Hoffman · Jun 22, 2017

Probably with something like this, but I can't imagine how much they cost-
Rollomatic SA – Precision CNC machines for cutting tools | GrindSmart(R)Nano6

gerritv · Jun 22, 2017

Or this method: using laser Laser manufacturing of fluted tools - YouTube

William Ward · Jun 23, 2017

Hey thanks for the replies. The opposed wheel grinding method makes a lot of sense and the comment about the carbide grain size is something I had not thought of.
Grinding wheel grit size jumped out at me because under the 'scope they appear to have no dead spot on the end in the center of a 2 flute end-mill. I do know if you look at them cross-eyed they break but with the right speeds and feeds they last quite a while in Copper-Tungsten.

Edit: Just looked at the Laser video. That's pretty cool. Not much info with the video other than 1 mm dia.

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How are miniature endmills made?

William Ward

Cast Iron

Milland

Diamond

ballen

Diamond

Conrad Hoffman

Diamond

gerritv

Aluminum

William Ward

Cast Iron

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