"DoN. Nichols" wrote in message
...
On 2016-11-30, Jim Wilkins wrote:
"DoN. Nichols" wrote in message
...
On 2016-11-29, Bob La Londe wrote:
So... any words of advice on counterbores?

.....
Of course -- you *can* simply use a two-flute center cutting end
mill to counterbore before you drill for the screw's shank and not
need
a piloted counterbore at all -- but if you are doing the
counterboring
in a place where the milling machine can't reach -- the changeable
pilot
counterbore might be the only thing which can reach and works.


I haven't had a problem countersinking with a 4-flute end mill, all
I
had in that size, after drilling the screw shank hole.

O.K. *after* drilling the screw hole -- or if it is a
center-cutting 4-flute endmill. Note that some 4-flute endmills are
not
center cutting. Look at the center if the end. If it has a center
hole, and a recess ending in a flat, you have to have a hole
pre-drilled, at least as large as the center recess.

Enjoy,
DoN.

Some of mine were center-cutting until I reground them. Now I have to
zigzag them back and forth to plunge a blind slot.
--jsw