Broken Off Allen Wrench in the Prop

[Nicholson58]

In our machine shop, we sometimes touch the end of the broken part with a welding rod. The rod will fuse to the broken part and make the joint hot. This often frees the offending part on the spot. If there is enough showing, select a hex nut and weld the broken part to the ID of the hex nut.

The difficulty of drilling I am sure you know is that the tools will try to walk off into the bronze.

[a64pilot]

Be prepared to drill out the whole screw, then tap the hole and install either the next size larger, or use a threaded insert. Do NOT go the easy out route, once you snap off an easy out in the screw, nothing will drill out an easy out, that is very hard steel, I know from experience.
Slotting the screw with a Dremel and using a regular screwdriver is an excellent suggestion, even if the slot has to cut into the surrounding metal as well as the screw, using a chisel if you can get to the sides of the screw is also an excellent suggestion, but usually if you can get a chisel on it, you can get vise grips on it too, and I assume you can't

[foolishsailor]

DH,

Been is a similar place myself. As bornyesterday suggested the way I got out of it was to cut a slot into the offending part. I had a 4mm SS screw snap below the surface and took a small metal chisel and made it narrow enough to not damage the threads, this needs to be done on a grinder with water to quench OFTEN as to not let it blue and ruin the chisel.

I then very carefully, as the screw didn't break level, knocked a slot into the screw and removed it with a screwdriver/hammer/heat...

Problem with tapping this out is whether you have a flat surface to get the drill bit to set without it sliding to the side and screwing your threads.

At the end of the day you will be lucky to not have to drill and re-thread anyway....

Edit: oops like like A64 beat me to it, what he said....

[skipmac]

I broke off an EZout trying to remove the allen screws in my prop shaft strut. Those are bits definitely as hard as any allen wrench. I tried titanium, HSS and ever kind of bit I could find to drill out the EZout and barely made a dimple in it, even after a couple of hours work, with cutting oil I might add,

Got a tungsten carbide grinding bit for my little Dremel tool and cut it out in 5 minutes. Now have a selection of tungsten bits and grinding tips for my Dremel and grinder. Don't leave home without it.

PS.
I had sworn off using EZouts before after a similar experience. This time I promise, never again. #%#$!!!!! EZouts.

[skipmac]

Another benefit to the tungsten grinding tip in the Dremel. You can easily start a guide hole in the center of the broken off piece and, if you're careful, just cut out the offending bit and not bugger the threads or hole that's blocked.

I find that once you cut a pretty good hole down the center of the broken bit it's usually easy to get the rest to pop out.

[Phoenician]

Quick suggestion in case you end up finding that you need to tap the next size bigger thread:

Before retapping, if your original thread is metric, try to fit the nearest SAE size screw (or vice versa), assuming you can easily find both metric and SAE screws in the UK. I've had good experience doing this, saving me the trouble of retapping, something I hesitate to do (given my limited metal working skills), particularly if time is short

[fstbttms]

Problems with Autoprop just never seem to end, do they?

[perchance]

Try going in with a pin punch and lightly tap tap tap the end of the wrench stub and see if it loosens.

[hellosailor]

If it is large enough so you won't accidentally hit the sides of the socket? Another vote for arc welding. Just hit a welding rod to it, let it cool, pull it out.

If you can pick up a can of "freeze spray" (Loctite sells it) you may be able to simply ice it down, whack the opposite side with a mallet, and watch it shoot out. Some PBlaster to loosen any corrosion, and some alternate hits of freeze spray (or a CO2 bottle, or dry ice in alcohol slush) and heat may also encourage it to move. Again, whacked from the opposite side to encourage it to jump out.

If it broke very cleanly, you might be able to use a spot of crazy glue to bond some other rod to it, and then pull it out. Again, only if you can do that without hitting the walls of the hole, although a torch would undo that.

Depending on what tools of destruction you have access to...

And throw out the rest of those cheap wrenches!

[Tellie]

An hour or so not a lot of time for these somewhat delicate jobs. But since the cheap allen key broke of in the head then it is not threaded in. As others said the corrosion may have sealed it in or may have deteriorated the cheap metal enough to pick it out. I've used JB weld before on the end of the same sized round stock or bolt and basically glued it to the broken piece and wiggled it out when the JB weld set up. This of course takes steady hands and careful use as not to glue the stock to anything else.

[Wotname]

Hmm plenty of helpful advice so far so perhaps it's time to take a different tack.

This type of job calls for some dentistry skills and although suggesting getting your local dentist down for a looksee is not helpful, it might help to actually think like a dentist here.

In essence you have some soft material stuck inside some hard material in a very inaccessible part (that can't be removed for easier working).

So seriously take along some good quality dentist picks - can be obtained in good tool stores - you don't want cheap stuff here - or perhaps you have a dentist mate to get some picks.


Try the least destructive methods first before resorting to welding / drilling as once you go down that path, the odds are that you will need to travel a long road before success.

Amazing what some decent heat (MAPP or similar) and then freezer spray will do. Hit it with that and then use the picks.

Keep the welding / drilling options for the next time when you have more time to play.

Good luck and I hoping to see you post that the broken off wrench part has already corroded out and just pops out on first or second try.

[bornyesterday]

Hi Dockhead,

I've just watched two Bruntons installation videos on youtube. From your description of the locking screw I'd guess you might have this version which fits a standard tapered shaft, not a splined saildrive shaft.
That's lucky because the nut of the saildrive version is recessed about two inches and has two lock screws. Not clever.
If yours is like the one in this video:

https://www.youtube.com/watch?v=GWV_BCwDR7U

then the locking screw looks too deeply recessed to use a normal cold chisel or dremel disc without some damage. Screw looks to be M5, IMO too small for welding, but just might be M6.
Looks identical to my prop - which is in the water so can't be sure. Mine's a 1980's boat so I might have an earlier model.

The video shows the locking screw bearing on the cylindrical part of the locking nut - not the flat - so worst case you might be able to force the nut undone even with a headless locking screw in place.

I'd still go with the modified cold chisel and expect to have the job done in about a minute - but if you can remove the stub quickly and the screw head isn't too damaged for a new wrench to fit - go for it!

[sy_gilana]

...and use a left handed drill bit, if it bites it undoes the bolt.
Seriously though, I think it will be gone when you haul...

[a64pilot]

These things often work and won't beak off like an easy out http://howto.homedepot.com/videos/wa...ome-Depot.html

[sww914]

I would-
Get a couple of spare screws
Get a special drill bit and a special screw extractor.
Throw the bits and extractors in the water as you approach the boat because that's all the good they'll do you.
Find some nuts whose holes are close to the outside of the screw head, 6 or 8 of them.
After hauling the boat, try to knock out the stuck portion with a punch and screwdriver like you first suggested.
After 5 minutes of that, I would hold a nut over the offending screw head with
Vice-Grips. I'd whip out my handy-dandy mig welder and weld to the screw head through the hole in the nut and right on out until the nut is full.
I'd turn the whole screw out with a wrench. The nut might just break off, that's OK, you have 5-7 more of them and keep trying.
Install a new screw.
I've made LOTS of money doing this trick.