Broken Off Allen Wrench in the Prop

[HappyMdRSailor]

This has all the making of a great contest....

Whichever method is the successful one... The winner is the first one who described it in detail...

Of course... We all suspect the offending bit to be gone too... In which case DH is clearly the winner...

Maybe DH still has a few of those extra B&G displays laying around....

[BentP]

I would suggest that the broken allen key is such bad quality steel that it should be quite easy to drill out. No need for space science here, drill a hole and use a tap driver to get the d... thing out

[Dockhead]

An unbelievable wealth of knowledge on here -- thanks very much to everyone who answered. This was incredibly helpful.

I also hope that when the boat comes out, the stub will already be gone. The prop has been spinning in the mean time -- maybe it just got slung out.

Yes, it's likely bad steel and maybe it won't be impossible to drill into it. I have the remaining part of the tool and will experiment with different drill bits before the lift.

Suggestion about dentist's tools is clever! I will definitely try that out.

I don't think welding is going to work, because the bolt is recessed deeply into the bronze. It will make a mess.

I think my main hope is either to pry out with dentist's tools or drill a hole in the stub and tap it for a screw.

If that doesn't work, looks like I'll have to drill it out, in which case I'm really screwed -- it means I'll have to send the prop back to Brunton to be repaired somehow, and rebalanced. Fortunately I do have a spare prop, but it's a fixed one which will be terrible for sailing and for reversing. Brunton will take some time (and $$$) for the repair -- it will be a real PITA.

[Dockhead]

Just had one other idea -- maybe I can force the prop nut off despite the locking bolt -- breaking off the tip of it. Then remove the prop, and deal with it in a machine shop with access from both sides and plenty of time.

[SailFastTri]

Originally Posted by 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

I once had this happen and was able to grind out the broken easy out using Dremel chain saw sharpening bits. It took several of the Dremel bits but they come in 3-packs and are inexpensive. It also took patience.

[SailFastTri]

Originally Posted by Dockhead

Just had one other idea -- maybe I can force the prop nut off despite the locking bolt -- breaking off the tip of it. Then remove the prop, and deal with it in a machine shop with access from both sides and plenty of time.

Overcoming that lock bolt will likely do some damage. Bear in mind that force or banging can damage your transmission and engine seals or bend the shaft a few thousandths or more. If machine shop is on the table, is it possible to slide out the entire shaft/prop assembly and bring it in? (Do you have an older shaft or other way to plug the shaft hole?)

[SailFastTri]

The Dremel chain saw sharpening bits come in small diameters and you can grind with just the points. They don't wander to the side like a drill would, and are much easier to control.

[minaret]

Originally Posted by Dockhead

Just had one other idea -- maybe I can force the prop nut off despite the locking bolt -- breaking off the tip of it. Then remove the prop, and deal with it in a machine shop with access from both sides and plenty of time.

I believe you are over thinking this. You should be able to drill and tap fairly easily. Slow RPM, lots of cutting oil, and a fresh cheap bit or two which you will throw away when done. Use brad point bits to prevent wandering. It's easy. Don't forget a bottoming tap. Not sure why everyone thinks you need to back out the screw either, just tap it for a fastener, install the fastener, then grab it with vice grips. Hit it with heat and oil and then just pull that sucker out. You'll never get a dental pic between the side of the wrench and the fastener.

[HappyMdRSailor]

Originally Posted by minaret

I believe you are over thinking this. You should be able to drill and tap fairly easily. Slow RPM, lots of cutting oil, and a fresh cheap bit or two which you will throw away when done. Use brad point bits to prevent wandering. It's easy. Don't forget a bottoming tap. Not sure why everyone thinks you need to back out the screw either, just tap it for a fastener, install the fastener, then grab it with vice grips. Hit it with heat and oil and then just pull that sucker out. You'll never get a dental pic between the side of the wrench and the fastener.

I think minaret is right on this... I re-read my post, and apparently had a massive brain fart going directly from removing the piece to drilling out the whole assembly... Instead of the vice grips above, I personally would pick a fastener/sturdy washer combo that would work as a "puller" against the hub hole.... adding a thin washer as the piece comes out... or extend the washer assy just beyond the hub, and use a screwdriver on each side for a puller effect

[sww914]

I just remembered another option. Some machine shops have a newer technology to deal with this sort of thing. It's a machine that uses a tungsten electrode and a small dam around the hole to hold some special liquid. They lower the electrode into the liquid and zap zap zap zap the offending metal away one layer of electrons at a time. It takes hours but it will be faster and maybe less expensive than returning the prop to the manufacturer. I think it's called MDM, Metal Disintegration Machining.
I seriously doubt that you'll be able to to drill it.

[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.

[sww914]

Tools are hardened.

[ranger58sb]

Is any of the allen key protruding? If so, would the right size (maybe magnetized) nut driver bit fit perfectly over the remaining stub of allen key? If so, I'd think one possibility might be to use that to wiggle the stub loose from its jam and retrieve it...

-Chris

[David M]

I have to ask, was the Allen wrench made in China?

I have learned the hard way to avoid tools made in Taiwan or China. Ideally I try to buy US or Japanese made tools. I know it is impossible not to buy a Chinese made tool occasionally since the vast majority are made there now.

[bornyesterday]

Originally Posted by Dockhead

Just had one other idea -- maybe I can force the prop nut off despite the locking bolt -- breaking off the tip of it. Then remove the prop, and deal with it in a machine shop with access from both sides and plenty of time.

Yes, you probably will be able to force the nut off.
How on earth did you come up with that idea?
If you do force it you might want to give a thought to what the other end of the prop shaft is doing... and have a spare nut on hand, maybe a couple of screws.

Good luck.