Screw Removal - Hull Split Line

[DLouth]

I have a re-core & transom repair project underway and I need to split the deck from hull. It's mid-70's CSM in polyester. There are ~70 screws fastening the rub rail over the lap joint, and another 100+ through the laminates in the lap joint.... 170+ rusted, stainless steel, #1 Phillips self taping screws to remove. So far I have tried:

• hand driver
• electric bit driver
• manual hammer-type impact remover
• soldering iron to heat & loosen screws in poly
• micro-torch to heat & loosen screws in poly
• cobalt drill bit

I got one screw out after 5min w/ hammer impact remover, so I know what the screw looks like... but have not been able to repeat after multiple tries. I broke one screw head off, and the rest just striped the Philips in the screw. Heating to point gelcoat started to turn brown did nothing. And the cobalt bit didn't cut a single chip out of the screws.

I now have a cobalt drill bit and some naval jelly - thinking removing the oxide and cutting with a real drill bit might take off the heads - then hoping a mini-roto-broach piloting on the screw shank/threads to cut them out, but this will leave me with a lot of swiss cheese to repair.

I've read multiple threads that say getting the screws out is a PITA, but haven't found how this has been accomplished by others. If anyone has any other ideas to try short of getting rid of or burning the boat, would be much appreciated.

[WaterZebra]

I have a re-core & transom repair project underway and I need to split the deck from hull. It's mid-70's CSM in polyester. There are ~70 screws fastening the rub rail over the lap joint, and another 100+ through the laminates in the lap joint.... 170+ rusted, stainless steel, #1 Phillips self taping screws to remove. So far I have tried:

• hand driver
• electric bit driver
• manual hammer-type impact remover
• soldering iron to heat & loosen screws in poly
• micro-torch to heat & loosen screws in poly
• cobalt drill bit

I got one screw out after 5min w/ hammer impact remover, so I know what the screw looks like... but have not been able to repeat after multiple tries. I broke one screw head off, and the rest just striped the Philips in the screw. Heating to point gelcoat started to turn brown did nothing. And the cobalt bit didn't cut a single chip out of the screws.

I now have a cobalt drill bit and some naval jelly - thinking removing the oxide and cutting with a real drill bit might take off the heads - then hoping a mini-roto-broach piloting on the screw shank/threads to cut them out, but this will leave me with a lot of swiss cheese to repair.

I've read multiple threads that say getting the screws out is a PITA, but haven't found how this has been accomplished by others. If anyone has any other ideas to try short of getting rid of or burning the boat, would be much appreciated.

If you can grind the heads off, is there enough length on the screw protruding on the inside where you can get a hold of it and twist the shank out with a vise grip?

[David - WI]

A "mini-ductor" would heat just the (entire) screw... red hot, if needed. Probably take 10 - 15 seconds each. Whether or not that's useful, I'm not sure.
https://www.theinductor.com/inductio...i-ductor-venom

[DLouth]

Mini-ductor looks awesome... going to get one of those to try - thinking of dozens of times this would have been useful in the past. What does polyester/CSM do when you get it real hot - turn to ash, melt? Either way could be helpful. Assuming wear a respirator.

Only about 20% of the screws are accessible inside of the boat - in cockpit - and some are sticking through. Haven't tried vice-grips, but will do. I did get one partially backed out before the phillips failed and tried to get a sharp claw bar on it, but wasn't out of laminate far enough.

[David - WI]

Mini-doctor is useful. We annealed a couple hundred hard bolts so we could machine them... use all the time for rusty nuts/bolts. Also, paintless dent repair if you're really careful.

[David - WI]

...and put the disc up under the shoebox fit hull-deck joint & cut the screws. may the force be with you...

If you're going to do that, you might be better off with one if those vibrating zip tools?

[DLouth]

Ok, getting caught up here. Thanks for all of the ideas/info. The rub rail is off... I only got 4 of 68 out of rub rail without destroying the screws. I don't know what material they are for certain, but multiple brand new high quality Cobalt bits just spin w/o making any chips. They are some stainless alloy or they would be completely gone after 50 years, but thankfully they have some ferrite as I explain shortly. Solid carbide drills cut great, but my $15+ bits lasted ~2 screws before shattering. In the end, I tried Milwaukee Carbide (tipped) Hammer Drill Bits and they cut the screws - were only $5 per drill and would take out 5-6 screws before they died. I also drilled heads off of a few of the hull split line screws and have a process that works - only ~100 more of these to get out. The tip from "David - WI" on the Mini-Ductor was the hot ticket! That and a very kind lady who met me on Sat AM outside of the closed local tool supply shop she works at and handed me the device. This thing turns screws red hot (literally red) in 4-5sec - and smokes away what I expect is highly toxic vaporized polyester. For the rub rail shanks that were sticking out of the hull ~0.125", I could just grab them and pull them out w/ side cutters. For the counter sunk screws in the hull lap-joint, it takes a few more seconds to turn them red and make smoke, but I can then drill off heads and just push them through into the hull with a punch. Oh yeh, after heating the screws, they turn pretty easy w/ P1 bit, but no material for threads to engage to back them out. Anyway - thanks for way more responses and ideas than I ever expected - much appreciated!

[rgsauger]

Damn. That’s nuts. Congrats on finding the right combination to get the bastards out!

[WaterZebra]

If you're going to do that, you might be better off with one if those vibrating zip tools?

Only problem with vibro saws is the blades for cutting metal (teeth) are junk. Never tried one of those tungsten particle blades though? Plunge cut thru shoebox hull joint would be easier than trying to get a spinning disc in there though (safer too).

[rgsauger]

The tungsten blades are crap. Save your money and buy two of the bimetal 18tooth or so blades. NOT impressed with the carbide one.