How to Remove a Damaged Setscrew?

[extropic]

I bought some used tooling items. One of the pieces is an end mill extension holder similar to the one pictured.



The setscrew (1/4-28) that secures the end mill is .125 long (calculated) so the hex socket (1/8") goes all the way through. I can see the flat on the end mill.
The problem is that the setscrew was over tightened by the previous user, and is cracked through one wall.
The socket is not particularly 'rounded out' but the crack allows the setscrew to radially expand, in the tapped hole, so the hex is now oversized by a few thousandths. A quality hex key cams around but doesn't fit well enough to loosen the setscrew.

I wrapped a hex key in a few layers of aluminum foil, in hopes of a better fit, but the foil just gets pushed out of the way at high torque.
I have various screw extractors and easy-outs available but I'm concerned that, because I have only 1/8" depth to work with, I'll have to grind (repeatedly) to get the necessary engagement before it bottoms out on the shank of the carbide end mill.
If I was a precision TIG welder, I might try to weld a hex key to the set screw (without welding anything to the extension), but I'm not, so that's out.
If I had access to a surface grinder I would have already modified a larger hex key to fit, but I don't where I'm at, so that's out.

I have some left hand twist drills and I think that will work, but certainly tear-up the drill.
I also considered taking a carbide cylindrical bur, in a die grinder, to the socket, opposite from the crack. That would get it done but I do hate generating all those micro slivers if not necessary.

What method/process would you suggest to remove the cracked short setscrew?

 

[tq60]

Diamond bit in a dremmel tool and a bit of time.

Sent from my SM-G781V using Tapatalk

 

[francist]

What about taking the next size up Allen wrench and gradually grinding the end to just go into the socket? If you grind at a slight taper (as would be likely anyway if you’re trying to reduce the size) you’ll have a tapering hex shape that might not be inclined to spin as much in the socket. You should be able to tailor that fit by gradually grinding off the tip of your tapered end until it’s just enough to go in but not so loose as to spin in the socket. All you sacrifice is an Allen wrench to try.

 

[Martin W]

If I had one I would use an electrical discharge machine. Since I don’t have one. I would probably use a left hand drill bit, since it could easily be re-sharpened.. if that didn’t work I would probably just bore it out with a carbide end mill.
Martin

 

[darkzero]

For me I would try these bits on the left, they're made for removing stripped hex socket screws. But they're from Japan so that doesn't help you any.


Since you said the hex really isn't rounded out, try a small flat head screwdriver that might fit tightly. Or try torx bits or the next size up hex key in metric or imperial (whichever one is a closer fit). Don't be afraid to lightly hammer the bit in if it needs it. That's how all those bits pictured above are designed to work.

If those don't work I'd try a LH drill. You mentioned being worried about damaging the drill bit. I'd sacrafice a drill bit for a tool that costs much more than the bit. Could probably just resharpen the bit if it doesn't break.

 

[SLK001]

Carbide burr in a drill press set for high speed.

 

[alloy]

I've had pretty good success getting set screws out using a torx bit. Find one that just starts to go in the hex and pound it in and it grips and so far for me I've been able to get every one out I've tried this on.

 

[Jake M]

With a crack in it, I wouldn't use anything that's going to expand it. I'd be very inclined to drill it out with a lefty, but if it's as I'm picturing, I'll bet it's already swaged in there, bigger than the threads. The geometry on those allen keys is a bugger, the outward force is just ridiculous compared to what you apply. Multiply that times a 200 pound gorilla who's end mill is falling out, and it might well be kinda stuck where it is, in addition to being tight.

I'd guess (that's all I can do) that this little set screw is about the same hardness as a normal socket head cap screw. You can drill 'em with high speed steel if you're on your A game. Good and sharp, slow speed, good pressure. Unless somebody found one of those that's fancier than I have, it's just standard grub screw, only short and the pilot is already drilled.

There oughtta be a law against those little screws. I think they were designed to be a jam nut, to keep the real set screw from backing off. Then you can push your allen key through it to get to the main one, and run them in and out together. I've never seen them used that way though, always loaded up with something too big for it to hold. And in a place you can't reach it. Not enough threads to hold much load at all. At least you can reach yours... That's a bonus.

 

[extropic]

All Done.

I first attacked the hex, opposite the crack, with a carbide bur in a Dremel tool. At under 1/8" diameter the bur teeth were very fine and generated dust rather than slivers. It was a long tapered conical bur. I use the past tense because it grabbed and ran around the hex until it became a short tapered bur. Oh well (humming Taps), it got the job done.

I figured the setscrew was on it's last legs by then so I tried the left hand drill of the style from a screw extractor set (example pictured). The setscrew broke loose immediately and came out in three pieces. No damage to the drill. Bingo.

Thanks to all the contributors. There are good ideas, from the contributors, that I didn't think of and hope to remember for next time.

 

[markba633csi]

Maybe you could put the assembly in a vise, then - never mind I see you got it