What's the definition of an end mill?

[Swiss]

Hi all,

I used to think that a flat bottomed cutter with no radius was called an end-mill and a round bottomed cutter was called a ball-nose.

Now I've noticed that a couple of people refer to "ball nosed end mills". Someone else told me that an end mill was any cutter that could cut at the end, as opposed to a horizontal shell mill.

Can anyone clear this up for me?

many thanks

hugo

[SRT Mike]

Probably a semantics thing. Here we definitely call it a ball-endmill, and so do the tool suppliers. Actually I think over here "endmill" means any cutter on the end of a rotating shaft. Most folks refer to non-centercutting mills as endmills too, including convex/concave cutters, as well as chamfering endmills and shell endmills.

[Geof]

I suppose you could say any cylindrical cutter that is held at one end, has cutting edges on the other end and extending along the periphery which are for the purpose of removing material when the cutter is rotated about its axis and traversed across a workpiece or plunged into a workpiece, is an end mill.

And I deliberately tried to make that description/definition as long winded as possible .

As SRT Mike says there is an element of semantics; after all a lot of 'end' mills are non-centering cutting so you really cannot plunge cut, they are really side mills. And a cutter that fits all the functional criteria I mention above that is put in a woodworking router is a router bit. And a two flute cutter that can plunge cut because it is center cutting can be called a slot drill.

Also to add to what you mention an end mill with the sharp corners between the bottom and sides slightly radiused is a corner radius end mill or bull end mill. A bull end mill leaves a radius between the side and bottom of the cut when it traverses along the material. However, a corner radius end mill can also be one with a concave radius that is used for corner rounding.