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Removing Cross-Threaded Screws from Hardware?

Posted by Cliff on from the tricky-situations dept.

TeaDaemon asks: "I currently have an expensive (dual CPU) motherboard mounted in a rack case. One of the mounting screws is cross-threaded, preventing me from removing the board. The case is designed to prevent access to the back of the risers, so that's not an option. Does anyone have experience with this sort of problem? Can anyone suggest a reliable way of removing said screw without damaging the board or any of it's components? The screw is next to the PCI slots, and has a couple of capacitors and ICs near by. Any help would be greatly appreciated."

4 of 58 comments (clear)

  1. LH drill bits. by frankm_slashdot · · Score: 4, Informative

    use a 2mm or 3mm LH drillbit. drill it out, and when you remove the board, just replace the standoff.

  2. Drill it out by photon317 · · Score: 4, Informative


    The obvious answer is to drill it out. Since you'll want to be a little careful, you should probably start with an extremely small bit and drill a pinhole into it first, and then work up the bit sizes one by one until the head pretty much falls off the screw. It will destroy both the screw and the mount, but they were crossthreaded anyways.

    The obvious issue is of course metal shavings. A small amount of cutting fluid on the bits (or probably any liquid, maybe wd-40) will help to a small degree to keep the shavings from flying around as much (they'll tend to travel up the grooves in the bit instead). More importantly - mask things off. Cut a small 3/4" or so square hole in the center of a large peice of paper. Cover the hole in masking tape. Place the taped hole over the screw, taping the hole down all around it - then cut the circle of tape off the head of the screw where you'll be drilling. You should be able to keep the shavings on the peice of paper instead of on the motherboard shorting out little pins and things.

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  3. Screw Extractor by adamy · · Score: 5, Informative

    The one thing I've seen missing from these posts is the use of a screw extractor. Once you have a small hole drilled into the screw, replace the bit with a screw extractor. This is a wedge shaped bit the that has flanges designed to dig in to the hole as the bit is on reverse. You might have trouble finding one small enough for a motherboard. But it may save the housing , and you will have only lost the screw.

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  4. Drill once, then use a screw extractor by Anonymous Coward · · Score: 5, Informative

    Once you've drilled the first small hole you can use a small screw extractor (basically a reverse threaded screw) to get it out. The idea is that you screw the extractor into the hole you've drilled in the stuck screw you need to get out, and once it "bites" you should be able to thread it out.

    I use them all the time when working on my car. It'll take alot less time and have the added benefit of producing alot less shavings.

    Plus it's an excuse to buy more tools! :)

    Here is a page that describes the use of a screw extractor if you aren't familiar with them:

    http://www.bluepoof.com/motorcycles/howto/screw_ex tractor/