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John McCoy

wrote in :

On 24 Jul 2016 02:01:38 GMT, Puckdropper
puckdropper(at)yahoo(dot)com wrote:

wrote in
m:

*snip&trim*

Oh! I just remembered something important: Not all end mills can
be plunged into the work. Those that can are called "center
cutting". Be sure to look closely at the end before buying a whole
bunch of them. Generally, 2 flute EMs will be center cutting.

Wouldn't there have to be some sort of cutter over the end?

The ones I've seen that weren't center cutting (and this by far does
not represent any meaningful percentage of the ones out there) were
sharp on the ends to the point where the 4 flutes came together. At
that point, it wasn't sharp. Those EMs could be ramped down into the
work, but couldn't be plunged.

I was wondering how those worked. IOW, they don't plunge (they aren't
a drill).

Yeah, that's the difference between "center cutting" and
"non-center cutting". The non-center cutting are designed
to cut on the side of the mill - the workpiece is moved
under the cutter from the side, as if you were cutting a
groove or rabbet. The center cutting type are designed to
cut on the side or end, so they can be plunged into the
work and then the workpiece moved (e.g. for a stopped
groove).

If I remember correctly (unfortunately my machinist friend
passed away earlier this year, so I can't ask him) the non-
end cutting mills clear chips better, so can cut faster in
a production setting. Which is why both kinds exist.

John