Can round carbide endmills be adequately held by setscrews

Not a prayer that a setscrew will hold without a flat. But you can grind your own flats with a diamond wheel. They don't have to be pretty to work, but should approximate a the slope-sided flat one sees on endmill bits.

Joe Gwinn

Joseph Gwinn fired this volley in news:joegwinn- snipped-for-privacy@news.giganews.com:

Iggy, the "slope-sided" ones are variously called "safety flats". If a flat is ground - well - _flat_, then when the setscrew loosens a bit, the bit can creep free of the collet, unless the flat has a "stop" near the butt of the bit.

When a taper is ground into a flat with the taper moving toward a larger diameter closer to the butt of the bit, then any creep tends to snug up against the setscrew again, lessening the chance that it will remove itself. It also will make the bit loose in the Z-axis if the setscrew creeps out. But that's better (for safety) than having the bit fly out under power.

Such has long been used on woodworking equipment, although I seldom see it on metalworking machinery.

If you have the tools, and are willing to carefully mark out your work, you can cut a vee-groove "flat" to engage the setscrew. This will essentially lock the bit in place, while minimizing the Z-axis looseness if the setscrew backs up some.

LLoyd

LLoyd

Lockheed commonly used that tapered flat on their end mills - tons of (literally) them out here about a decade ago

Very, very doubtful. At least you don't have to worry about the carbide shank getting mashed and never getting the tool out of the holder again, but no, it will not hold the cutter securely. There is a REASON they put Weldon flats on endmill shanks.

Jon

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 are:

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:

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

Good Luck, DoN.

So, I think the conclusion is to use colleted holders for those end mills. I got those too.

i

FYI, they use inductive heating both to expand the holder for receiving the tool end, and to expand it again to release the tool. They come in two price ranges: expensive, and outrageous. The cheaper or smaller models often don't do a good job of releasing HSS shanks, but all of the brand-name ones work well with carbide.

These are for commercial work, and, as you say, they were designed for use in high-speed spindles. However, companies that adopt them generally use them for all of their mill tooling.

You can see good examples at the Biltz website. They also make many of those that are house-branded by other tool companies. I'm drinking coffee at this moment from a Biltz car cup.

You've gotten lots of good advice, but to recap, if you have smooth-shank carbide end mills, they were probably expected to be used in one of several types of collet-type toolholders. You aren't likely to get a good grip with setscrew toolholders. You may also have problems with them because they don't center the tool very well, and carbide is brittle, not liking off-center toolholding.

However, there are Weldon-shank carbide endmills around, so it must work. As others have said, you'll probably have to nick them to make a seat for the setscrews. You might get away with a silicon carbide grinding wheel, but my guess is that it will just frustrate you. Maybe a diamond tile wheel will do it, if you have a tool that will hold those wheels.

Good luck.