Broken Off Allen Wrench in the Prop

[jeepbluetj]

A cheapie bicycle allen wrench. I'd guess not hardened well.

Been in the water a year.

What're the odds that it just has completely corroded away?

[natew]

Well it's either already disintegrated into the ocean or it has corroded and swollen up so bad you will never be able to remove it.

A thought since we all seem to be concentrating on removing the broken tool... Why not just have another nut welded right on top of the existing nut or whatever it is, take the whole nut and everything else out and replace the nut with a new nut. Throw the whole thing out, broken tool and all, and replace it. I would honestly go that route because I think chances are pretty high that even if you manage to pry out the tool somehow you will probably find that the hole that will be left behind has either corroded away or has become so stripped and mutilated from all the tooling that you will have an equally difficult time using any tools to retighten the nut without damaging it further.

[Ocean Diamond 2]

Hi all,
Yes some great ideas and the dental tools are what I use, as I'm heavy handed and end up in these situations all the time.
My advise is to go to the local dental technician , not a dentist, see if you can borrow his special dremil tool that spins at 50000 rpms and a couple of his tungsten rose heads and or fissure burs and just cut it out. They are small and whip out the cheap steel in no time.
I keep a dental hand piece on my boat and it has a lot of jobs.
Derek

[minaret]

Originally Posted by captain465

Center punch the offending broken allen wrench bit using a "transfer punch" (OD selected to fit in the "tunnel" of the prop set screw. The OD of the transfer punch ( a type of pin punch, with a point ground in the center like a drill bit, and hardened). Since you are removing a lesser diameter bit from inside the set screw, it is essential to "dimple" the broken bit so that you have a place to begin the drilling process. Once you have your starting point, by all means, use a COBALT drill bit to drill out the broken bit of allen wrench. Use plenty of coolant, and go slow in the drilling process.......let the tool do the work.....too much pressure or speed will overheat the drill bit and the broken bit and make things more difficult. You are attempting to remove a somewhat hard material from within a "tube" of softer material ( bronze), so accuracy is prime.The drill bit should be of the same ,or somewhat less of the diameter of the allen wrench. (easy to determine, since you still have the old tool set).

Good luck, and let us know what ultimately works for you.

PS the machine shop removal of a broken screw or stud is called "EDM", but requires you to be able to remove the prop to the machine shop, which, under the circumstances is not possible.

No punch required, just tap on your disposable brad point bit with a hammer first to seat the point. Quick and dirty.

[charliehows]

with one hour on the stand to work with I'd be diving on it to get a real clear understanding of its condition before i started planning the fix. Like you said - its an allen tool so theres nothing much holding it in - theres at least some chance its been thrown out in operation. My first choice if its still there would be picks, just try and work it out. 2nd; the quick and dirty welding rod - try it on the broken tool to figure what kind of rod you need. 3rd; drill and wiggle, 4th tap and screw, 5th smash up a 44 gallon drum with a REALLY big hammer til you feel better.

[Blue Crab]

DH, like everyone, I wanta see how this plays out but I don't see this happening in an hour. Drilling small tool steel with a handheld drill motor ... and in a hurry? Ain't gonna happen if I do it, that's a fact. I'd love to be wrong.

May it have corroded away.

[Therapy]

Originally Posted by Blue Crab

May it have corroded away.

+1.

I can't come up with anything anybody else is not already suggested.

I can't even decide what I would start with first.

Best of luck.

[Wotname]

Don't forget to use heat (gas torch - MAPP etc) and freezer spray before using the dental picks.

The heat and cool will make a big difference is loosening the bond between the broken wrench and the screw, especially if there has been some corrosion between the two.

[ironworker]

I would try to find a drill bit that cuts anti clockwise and heat the Allen head. If this don't work I would cut the nut in half being careful not to cut into treads.

[Wotname]

DH, let's assume you have removed the broken Allen wrench from the safety bolt!

Depending on method of removal you may find the hex socket is now somewhat damaged thus making it a loose fit with the new quality wrench.

If so, try putting some coarse valve grinding paste on the wrench (or in the socket head) before inserting the wrench. This will allow the new wrench to "grip better" with the damaged socket head.

Again, good luck -when is the big day?