Cracked Set Screw

I was taking a bunch of tool holders out of service the other day, and I couldn't get the set screw out of one in order to push the tool out. It felt like the set screw was rounded out, but the set screw looks ok, and a long handle hex key seemed to feel ok in the hole.

This morning after firing up the shop and getting jobs cutting I took a look at it, and the set screw is cracked right down the side. When I try to turn the screw the crack widens up and the wrench pops around inside the hole. Its not a big deal I guess. These tool holders only sell for around $50 used, but hey. $50 is $50.

Any suggestions. I have considered trying to tap in an oversized hex key, but its right there. I have a drawer full but I haven't found that one that feels like it almost wants to fit. =======================================================

Go to

and put 2892 in the search box to see that catalog page. They have tapered hex keys that you drive into a stripped head and then turn out with a wrench. I've used the M5 size at least a dozen times (although a Torx T20 does that job well and is usually handier) with success. They have ones for socket cap screws and ones for socket set screws, not sure what the difference is, maybe the length of the taper. Anyway, maybe it would expand the screw against the threads and grip well enough to turn it out without galling the threads? If you have a sacrificial hex key that is a size too large you could grind your own taper and try that (and save the $12.50 :-)). With the crack you probably want a pretty steep taper, anyway.

I buy 1/8, 5/32, and 1/4 inch by the 100ct box because I package hex keys with molds so the customer doesn't have to hunt one down to use the mold. (clamping screws, slidebar retention, etc) This set screw just happens to be 7/32, so a little work on a 1/4" on the belt sander to make my own tapered key might just do the trick. Thanks. Even if it doesn't do the trick its a great idea.

drill bit yet ?

Any friends have an EDM machine?

BobH

Is the other end mushroomed?

ty

If you are going to buy a left hand drill bit I would go for carbide. Set screws are pretty hard.

I have used a Harbor Freight little turbine ( mini air die grinder ) with d ental bits to get out broken taps.

Might try a dremil tool and a diamond rotary file. The diamond rotary file s are pretty cheap on Aliexpress.

Is there enough space to use a cutoff wheel in a Dremel tool to cut off the part that's pressing on the toolbit? That would take the pressure off and should allow the screw to come out easily.

Or a Robertson or torx driver?

That depends on what kind of tool holder is being discussed. I was thinking about the end-mill holders which I use in NMTB-40 and NMTB-30 size, and those have no exposed part of the setscrew between the threaded hole and the tool being held, and the setscrew is specialized

-- a flat and a bevel just right to match the Weldon flat on the end mills, based on shank size. The bevels serve to set the length of tool extended beyond the holder. (This also makes it difficult to drill out too, because the flat is about the minor diameter of the thread. I guess that a solid carbide drill could drill through the setscrew and into the shank of the endmill.

However, if it is a typical quick-change toolpost holder, there is a length of setscrew exposed, depending on the size of the tool shank vs the size of the slot in the holder. (My experience is with the BXA size holders, FWIW -- a 5/8" square shank comes close to filling the slot. Use a 1/2" shank, or smaller, and there is room for the cutoff wheel, if the wheel diameter is large enough to reach. And operate on the assumption that the tool is expendable, too, and you can cut deeper to get the play you need.

Oh -- and the quick-change toolpost holders typically have four setscrews, while most of the end mill holders have one custom setscrew, though I have seen a few sizes which have two setscrews, and the mills have two Weldon flats.

So -- what kind of tool holder are we talking about here? The price is within the range of used holders for both types.

Good Luck, DoN.