Harold & Susan Vordos wrote:
snip

You are losing me here. Assuming he can get a two flute end mill with a

1/2

shank and run his drill at the proper RPM why would this setup walk all

over

the place on a .1 deep hole? A new end mill will have its edges

concentric

with the center so this should not cause too much grief IMO.

--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.


While I value your opinion, my over 40 years in commercial machine shops
tell me that when you plunge cut with end mills, one side (or flute)
generally drives. It can be caused by chip loading, a slightly duller
side, a small defect in the cutting edge, the reasons are endless. My
suggestion to make a tool that is circularly ground (no peripheral relief)
helps avoid the problem. Counterbores are made thus, and for that reason.

Working with large tools in a drill press that has little to NO rigidity is
a recipe for disaster. I am not of the opinion that it won't work, but I
am of the opinion that it works only for those that don't know the
difference between a milling machine and a drill press. Once you're used
a mill, even one as spindly as a Bridgeport (I can say that, I own one),
you'll fully understand what I mean. When you plunge cut with an end mill
of the needed size, especially when it's held in a drill chuck, which is NOT
intended to hold heat treated items like end mill shanks, the chances of the
hole coming out even remotely the right size is almost non-existent. That's
true even in a milling machine, especially a spindly one.

In a drill press, runout of the chuck holding the end mill alone would
likely be trouble. The spindle will allow the end mill to wallow about,
and with the side relief of the end mill as it is, it's likely to hog in and
create lots more problems than one can settle. Instead of piloting on the
hole as it is generated, the end mill simply cuts away anything that gets in
the way when it wallows about. Personally, I wouldn't use a drill press
for any kind of milling. Even when they make the cut, the degree of
precision sucks, and the finish is likely to be something for which you'd be
constantly making apologies.

Hope this helps you understand my position.

Harold

Hi Folks,

Gotta agree with Harold here! I had the mill set up for some other
tasks and needed a quick and dirty counterbore a few nights ago. Had
the work clamped well on the table, used a nice US made 3/8 inch 2 flute
endmill - fresh out of the tube. Around 500 RPM, kerosene, and 6061
with a clearance hole already in it. Lined it up with the drill bit
used to poke the clearance hole, clamped down, verified no deflection of
the bit going in and out of the hole. In short, did everything as right
as I could for a half assed work around. I just couldn't control the
feed finely enough with the drill press spider. Grabbed, wandered a
bit, chatter out the wazoo... In short, a mess. Now my drill is just a
JET 17 incher, not an industrial grade machine. I tried playing the
mill on this drill press game years ago, accepted that it doesn't work
well, and saved up for a mill drill. Still not as heavy a machine as
I'd like, but the kids want to eat and there's only so much room and
money available.

Finished the previous work on the mill, then did the job using the same
endmill on the mill and knocked out the counterbore just fine, so at
least I didn't booger a fresh end mill. A piloted counterbore would do
just fine for this application in a drill press, but as I understand it
the desired result is really a round pocket, not a counterbore.

I really should finish up the counterbores I roughed out a while back
for these sorts of tasks, just haven't gotten to it. Don't counterbore
often enough to justify the cost of US made commercial ones, and avoid
PRC stuff whenever I can.

Cheers,
Stan