Allen Key Broke off and is Wedged in the Screw Head?!?!?!

teller

teller

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So, as the title says, I was removing a gas block this morning and the #$%*!! allen key snapped off flush with the machine screw head. Normally I'd just say screw it (no pun intended) and drill it out but I'd like to reuse the block and need the screw. I thought about using an extractor but I'm worried it will completely wreck the finish of the block (it's parked) not to mention destroy the screw in the process. I tried pounding the gas block with a mallet for a bit to try and dislodge the piece of the key that's stuck in there, but it looks like it deformed slightly when it broke. :bangHead:

Any suggestions or am I just SOL?
 
Take a piece of metal and heat it up to red hot. Something that fits flush against the screw head.

When you do this, the heat will be transferred to the screw, then to the broken off ball from the allen wrench. This will break the physical weld created when you applied to much torque. A quick tap with a small punch and hammer should loosen the ball enough to get it out.

Now, get this right. If you dawdle around after applying the heat, or leave it on to long and nothing will change, because the heat will transfer to the ball as well and it will exand exponentially and stay jammed.
 
Thanks bearhunter, don't know why I didn't think of that! Serves me right for using a bit vs a proper allen key...oh well, lesson learned fml
 
Crap, went to try the heated rod technique as per above and discovered that the broken bit is not flush with the recessed set screw, meaning that no matter what I do, I can't actually touch the rod to the screw without heating the broken off tool bit :(

Any other suggestions?
 
Thanks for all the help guys, this thing is being a real PITA. Can't do the tube idea since the set screw is tinier than the width of an AR gas tube. The dremel idea might work, but the darn thing is recessed so I'll end up messing the gas block up most likely. Nick, I think your idea will work, but the piece that broke off is tool steel, so, well, we'll see....think I'm fated to break out the drill press on this one :(
 
use a small automatic center punch and impact it afew times to break loose...i do this on 2mm broken hex keys once a week

if not, try a small hammer and a prick punch or small nail...just need to shock it loose...try to rotate it in the opposite direction in which it broken....then slap the whole assembly upside down on a bench to get it to fall out
 
The tube idea will work fine. It doesn't matter if you heat up the are around the set screw. Go for it. What have you got to lose.
 
hexbasher said:
use a small automatic center punch and impact it afew times to break loose...i do this on 2mm broken hex keys once a week

if not, try a small hammer and a prick punch or small nail...just need to shock it loose...try to rotate it in the opposite direction in which it broken....then slap the whole assembly upside down on a bench to get it to fall out
Click to expand...

My procedure as well.
 
I have a small baggie of Dental Burrs (the stuff the dentist drills your teeth with), which are carbide cutters. Dremel sells some that are not as small.

A Dremel tool works OK, a air pencil works better, and actual dentists drill works best of all.

In any case, a magnifying glass to have a good look, then carve away whatever is in the way. It can be slow going, but you can carve out the broken part, as well as the screw, with some patience and a light touch. I have carved out a lot of broken taps and Eze-Out tips this way.

You can use the same cutters to shape a slot in the screw to remove it. The screw is gonna be a write-off, but set screws can be got if they must.

Cheers
Trev
 
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