On 2010-07-25, Ignoramus1880 wrote:
I am anticipating an answer that I will not like, but anyway: I have a
number of carbide end mills (large number) and a lot of QC30 toolholders
that hold tools with a setscrew. Most of my endmills have no flats on
sides. If I hold one with a setscrew, is that adequate for real life
milling? I was able to mill machinable wax like that, but obviously
this is not a real test.

No -- you cannot expect to hold them with the setscrews in a QC
30-taper toolholder.

First, you will find that the end of those setscrews is flat,
with a bevel at the edge with is matched to the Weldon flat on the
endmills which fit it. This prevents the end mill from moving either in
or out.

Second -- normal cup-point setscrews depend on displacing part
of the shaft on which they are being tightened to get their grip. A
solid carbide end mill will *not* displace under any conceivable amount
of torque on the setscrew.

For those smooth-shanked solid carbide end mills, the ways to
hold them a

1) Slightly undersized end mill holders without a setscrew,
designed to be heated (by a special bench tool) to expand and
drop in the end mill and then gripped by shrinking the holder.
I believe that the same heating would work to release the grip
on the end mill so you can replace it -- but I have never
actually seen or used one of these.

These smooth shanked end mills are made for use at very high
speeds, and the flat and setscrew would set it off balance
somewhat at those speeds.

2) A *good* collet type holder in the 30 taper shank. This means
one of the several double-angle type collets which close
parallel, not the R8 collets which have a tapered grip on
anything other than a prefect fit between the collet and the
tool shank.

3) Something which would work very well -- *if* and only if the
bottom end of the shank had the right thread is a Clarkson tool
holder in NMTB-30 taper (or whatever the precise taper and form
are for your spindle.) These combine the thread for firm
retention, a center in the holder to limit the rearward travel,
and a collet to hold the rest of the shank concentric. This is
a design which is apparently common in the UK. I have a couple
of the holders in 40-NTMB (from eBay), but no matching end mills
yet, and I am not certain that the threaded shanks are available
for solid carbide end mills.

To see images -- start with this google search:

http://www.google.com/search?hl=en&q=clarkson+autolock&aq=f&aqi=g1&aql=& oq=&gs_rfai=

Then click on each of the images to see more about them.

Good Luck,
DoN.

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