Removing Broken Drill Bit

While drilling out 1 of 3 broken bronze screws that sheared off from one of the swim platform brackets, the cobalt drill bit caught an edge and snapped off inside the hole. Tried drilling that out with a slightly larger cobalt bit but it quickly went dull with no apparent progress made.

Outside of simply putting West System over it and drilling a new hole, anybody got any nifty tricks for removing a broken drill bit that still has part of the screw behind it? Was thinking of getting a punch and whacking the ba-Jesus out of it, but thought that may do more damage to what is still holding screw in. Appears there may be an encapsulated metal sheet with threaded holes that swim platform bolts pass thru on stern.

Also - I cannot get at hole from inside boat - the fuel tank is about 2 inches away from stern where this screw passes thru - so can't attack from that side. Thanks Guys - Scott

OUCH! That's the trouble with carbide/other hard drill bits (and easy-outs!). They are quite brittle and break much easier than regular bits. I assume it's a relatively small bit - 1/4 or maybe 3/8? Even so it MIGHT be possible to use a small pointed punch/chisel and try to set it as close as possible to the edge of the broken bit and tap it with a hammer, trying to turn it in the opposite direction and have it withdraw itself.

Failing that, I would leave the bit/screw remnants for posterity, flll over it and redrill a new hole.

Good Luck.

It was a 1/4" bit that snapped. I found these nifty drill bit extractors from a 4x4 site - http://www.peterson-international.com/safeandvault.htm

Think a punch would be cheapest way to start.

You'll never be able to drill it out except maybe with a carbide bit, and I can promise that will not work with a hand held drill. The smashing trick may work but with the risks you describe. I think Hatteras embedded an aluminum plate in the transom to attach the platform, so the stuff that's holding the bronze is fairly soft. Heat also won't work for obvious reasons.

The only thing I can think of is to see if you can get some stiff wire and drive it into the flutes. Then grab the ends of the wire with pliers or clamp some plates to it and see if you can twist it backwards a little and free up the edge that it's hung up on.

If you're comfortable enough with fiberglass work, you might want to consider using a hole bit around it. Then just fill the hole and start from scratch. Especially if you can make the hole small enough where it will be covered by the platform bracket.

Cool tool at Peterson website..good post...thanks

I have had success with spot welding broken bits say to a grade 8 bolt, the trick is to get a connection to the broken bit in something not ferrous.

On steel I have grounded the area and shoved an insulated bolt connected to my welder onto the broken bit and let it weld itself and then wrench it out.

This is a little trick that we use in our diesel shop to remove broken headbolts without removing the head. It has never failed and saved many a customer the cost of removing and re-installing a cylinder head

You need to be able to ground directly to the drill bit,it can be done with an old screwdriver or even a nail connected to the ground lead.If you do not,you risk welding it to the surrounding metal.

Using just a large electrode, with a small piece of vinyl or rubber hose around the end to insulate it from arcing on the wrong thing,hold the electrode directly on the broken piece.Have someone quickly turn the welder on then off. If you had experimented with amperage and got it right,before trying the real piece,the electrode will be welded to the broken bit. Remove the electrode from the holder,bend the top to make a 90 degree handle and hope for the best.
Good Luck Tony

Sounds neat - If I tried that I'd probably end up with a drill bit, electrode, and screwdriver all welded together and all of it still stuck to the boat! :)

That is a neat trick and just the excuse I need to buy a welder! Actually friendly with the yard manager, just may be able to buy into this experiment with his welder. Thanks for the tip.