Larry sez:
" That's what I was thinking, but what would an end mill do?
It's cutting a flat hole which would be less prone to that."

As far as being less prone to "skip", an end mill would be a little better
(but not much) for drilling straight down. Even then there are
uncontrollable side forces because of previous hole roughness, differing
texture in the metal, etc. And if the side forces don't get you, the design
of the end mill will . . . . that is to say; end mills make very poor
drills. We like to think of them as "good" drills but it just isn't true.
The end of a mill is designed for a plunge cut to get it into position for
"milling" - most of which occurs on the sides. Because of their design for
brief plunges, the ends of end mills have very poor chip clearances designed
into them. Extended "down" drilling will clog the cutting edges and destroy
the end mill via excessive heat. To be effective at all, a great deal of
peck drilling is required in order to not destroy the end mill - enough that
it is an inefficient way to proceed compared to a regular drill.

Bob Swinney


Larry Jaques" wrote in message
...
On Wed, 15 Sep 2004 04:30:51 -0500, "Tim Williams"
calmly ranted:

"HaroldA102" wrote in message
...

Well bud what if we move the part
alittle and bore stright down just take a little at at time???maybe .020
at a
time to be safe ???

No, the bit bends and walks all over. You have to go over at least 3/4
diameters, and even then it might skip into the previous hole.


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