Screw Removal

December 14, 2008

This weekend I replaced some rusty screws on the toilet seat with some new stainless steel ones.

I was trying to think why they became so rusty and believe that perhaps they were origionally zinc plated (BZP – bright zinc plate) and that the toilet had been cleaned using acid based cleaners. Anything that says “orange” or “limescale remover” on it will likely have acid in it. These will quickly disolve the zinc allowing the steel screw underneath to rust.

I’d tried to move the screws using a screwdriver but the heads just crumbled. So I thought, why not get myself some screw extractors. Screw extractors come in two forms. The fist looks a little like a 2 blade countersink bit in reverse. The other requires drilling and works a little like a reverse tap.

I was concerned that the tapping version might be fragile and snap. The simpler countersink like one looked more likely to be successful. I purchased some of these for a small price (approx £3 inc postage) and tried them out. My results were not very successful, the bit just skidded around on the screw head (even at very low speeds) and did not grip at all. I don’t know if this was a symptom of the heads being so rusty or not. I’ll give them another go next time I have some stuck screws.

I resorted to a simple drilling approach. I drilled through the heads of the screws with a drill bit approx 2/3 of the size of the head. This means that you don’t have to worry about being two accurate on being in the centre. It normally results in a nice little doughnut of metal detatching itself from the shank of the screw and minimal damage to the surround. This left a reasonable length (approx 3-5mm) of screw shank poking out of the wood and I used surgical callipers to unscrew these. I’ve previously used a junior hacksaw to cut a slot in the top of this shank and unscrew them using a flatblade screwdriver. The drilling method would be problematic if the screw was securing a very thin sheet as you would be left with little or no shank.

A friend has recently purchased the tap like extractors so it will be interesting to see if he’s had better results than mine.

Although I spotted this mini project myself, it’s quite common for the MSW to find such projects for you.

By Andy from Workshopshed Add Comment

  Posted in: Uncategorised Tags: rust, Screw Extractor, Zinc Plating