bad old screws

[jimstark]

I'm beginning to restore a Dunphy hot-molded "mahogany" runabout. The transom is held by hundreds of rusty steel screws. How can I remove them with minimal damage to hull/transom plywood?

Thanks for your help. I've searched the archive without finding a specific answer to this problem.

[Bob Cleek]

Tediously... that's how. Unfortunately, there are some jobs that just don't come easy. Use a sharp screwdriver that's the right size for the slots and do your best to back them out. A light tap on the end of the screwdriver before turning may loosen them some. Expect a lot of the heads to twist off and the slots to gall and be useless. There is a hollow centered drill on the market (check any of the good tool catalogs) that will drill a hole "around" a screw so you can get it out and then plug the hole. If you are trying to save the plywood, that probably isn't going to be worth the trouble if every other screw breaks on you. You may find it easier to rip off the old plywood, saving as much as you can as the pattern. Then take out the screws with a vise-grip clamped on them. Lay a whole new transom. It will definitely look nicer. If it is laminated, you may also lay a veneer over it as a solution. Steel screws in a boat isn't "finestkind" construction. You may expect to find other problems as you go along. Be patient, it's like pulling teeth. Eventually, you'll get them all.

[Concordia..41]

I use left handed drill bits on my size 14 bronze screws when the slot breaks out. By drilling slow in reverse with a battery drill, most of the screws back out when and if the drill grabs. If not I use an easy out in the hole that I drilled. I buy the drill bits from Grainger or MSC. I order extras as it takes time to get the feel of the drill and if I’m not careful I break the bit. Sears sells a screw removing set that I got but they don’t work on bronze. They my work on steel.

If I lose the head of the screw I use a bit I made up from spring pins. These I get at the local hardware store. They come with a slight taper on the end. I grind the taper flat and then cut cross groves with a file. The hole in the pin should be just smaller than the shank of the screw. I put this in the battery drill and drill in reverse. The bronze screw shank will gall and the pin will grab and back out the screw. This will make the hole in the plank larger than you want so I either use a larger screw or use a tapered reamer to enlarge the hole and epoxy in a tapered plug that I drill and counter sink to the original size. This also I have not tried on steel screws.

It all takes time but saves replacing a plank for a few damaged screw holes. And finding a 22’ long mahogany plank is not easy.

Dave

Sun over the foreyard

[Bruce Hooke]

I've found that a brace (as in for drilling) with a screwdriver bit in the chuck will turn screws that a screwdriver would get nowhere on. I think it's the fact that you can put so much more downward pressure on the screwhead as you turn that makes the brace work better. The key is to use the brace right from the start. Once the screwdriver has chewed up the head the brace will not help much. Of course your screws may be too far gone for even a brace to do anything.

[Ed Harrow]

Like Dave I've used roll (spring?) pins. What I'm talking about is a hollow tube with a split along one side (typically driven into an interferance-fit hole to hold something onto a shaft. I just used a triangular file to file a bit of a triangular shaped opening at one end of the split. Chucked the other in in the drill. Worked like magic on a small, brass screw, and barely touched the wood into which the screw was fastened. Don't know what would happen with steel. Good luck.

[imported_Spissgatter W-9]

I just finished replacing the last 500 or so #12 galvenized fasteners in the my project boat. After removing the old bung and cleaning out the groove carefully with a chisel and awl, I removed most of the fassteners with a 1/2" drive impact air wrench. It worked very well. The air pressure was set low so it would provide slow thumping impacts. Too high and it will spin off damaging the plank or twist off the head of the screw. If that didn't work, I would drill a pilot hole (sharp bit only) and use the standard tapered, four-sided easy-out. Steady slow pressure worked best. Avoid twisting off the easy out lest you find the center of the screw now filled with very hard metal. If that failed,(typically because the head or half of it came off) I would next use those "unscrewem's" or sharpened roll pins as previously descibed. When reduced to that option the hole was much to big to refasten as is. So, I cut tapered plugs out of red cedar (they look like enlongated pyramids); mixed up some thickend epoxy, slathered it on the plugs and then drove them home. Next day I cut them off flush with the plank and rebored them with bit and countersink. These screws had been in the boat for 60+ years. Some were in very good shape...some were dreadful. Anyway, they have all now been replaced with silcon bronze and bunged. I'm on to wedge seaming. Good luck. There will come a time when you are done with that task.

[jimstark]

Thanks for all the great ideas, friends. I'll probably use most of them before this job is through. I'll try to let you know how it goes.