Removing Cross-Threaded Screws from Hardware?

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."

Comments

LH drill bits.

[frankm_slashdot]

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

holy christ

[Anonymous Coward]

Thank god I ponied up my hard-mooched cash for that Slashdot subscription, so I could see this story nice and early!

Unfortunately, I've been sitting here with my jaw slack in stunned silence ever since it appeared. I keep staring at the screen, and it stubbornly persists in saying "Ask Slashdot," when I know, KNOW, that it really says "The Home Depot."

"Dear Slashdot, I cross-threaded a screw. What should I do?"

"Dear Slashdot, my toilet is backed up. What should I do?"

"Dear Slashdot, my grass is too tall. What should I do?"

"Dear Slashdot, my cat wants something, and I don't know what. What should I do?"

It's the end times, people. Repent and be saved while you still can, 'cause shit like this MUST be one of the signs of the pockyclipse.

Small drill bit.

[sporty]

If you can use a very small drill bit and clean out the hole just like a root canal.

Be very slow, very careful and try every so often to see if you can yank out the screw w/o killing the board.

Slow yes, but it'd work.

Drill it out

[photon317]

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.

Re:Drill it out

[PurpleFloyd]

Remember that the belt-drive system of a vaccum cleaner can generate a lot of static electricity. In the wrong circumstances, it can act like a Van De Graff generator. I would suggest using a specialized "computer vaccum" (basically a regular vaccum cleaner with a grounding system somewhere in the hose or motor assembly) or just blowing out the shavings with some canned air (be sure to get in the PCI and RAM slots!

Re:Drill it out

[SEWilco]

I was thinking of a "shop vacuum", a drum with a filter and blower on top. Stuff gets sucked into the drum, with most of it falling to the bottom or circulating around the wall until it slows. Often called a "wet/dry vacuum" due to being able to handle water. But small canister vacuums are also popular in workplaces, and those simply have a filter bag ahead of a fan -- that would be enough for drilled metal, assuming the fan motor doesn't mind being run for as long as this takes.

Static electricity is probably created by the airflow, so you're right that caution should be taken. Probably it would be sufficient to wrap aluminum foil around the hose a few inches from the intake end, with a grounding wire connected from it to the computer case. How the foil is held doesn't matter, as long as it is not with glue that might insulate it too much. The only static build up should be in the few inches to the end, and that could be reduced with one strand of wire somewhat coiled around the tube from the foil to the end.

But you might be using a stiff wire to hold the thing in place anyway, and if that is electrically connected to the case that should be enough.

That is, instead of making a copper sheath with a grounding strap it probably is enough to anchor a wire coat hanger in some holes on the case or rack, sandpaper or file it in several places to remove any insulating covering, and twist the wire around the end of the hose to hold it in place. Use whatever level of tech you are comfortable with, it's your rescue project.

I was suggesting sucking while drilling to prevent having filings stuck to components in ways which resist vacuuming after the drilling. Should be particularly effective on the smaller filings which would otherwise be most likely to get stuck in miniscule cracks.

Don't suck in any jumpers or batteries that you can't replace.

When done, tap the hose while in operation to try to shake filings out of hose to prevent their falling out on the next project.

'ask hardware store'....or try this...

[avi33]

First off, everyone should have one of these. The dazzling array of bits should help you brainstorm halfway out of any problem.

More likely you need a drill with a bit extractor kit.

Not really sure what specifics you're dealing with, but just go into a real hardware store (not a harware shopping mall like home depot) and ask the guy (or girl!) with the most nicks and scars on his hands. They could probably do it with a swiss army knife.

~a

Just a thought, might work, might not

[Webmoth]

Tools needed: 1 Dremel Moto-Tool (or equivalent) and an appropriate burr bit; 1 vacuum cleaner with smallish wand; 1 clear "safety cap" from a bottled water bottle; clear adhesive tape as needed.

Here's the idea: using the moto-tool, drill a hole in the TOP of the safety cap just big enough for the bit to pass thru. Also drill a hole in the side of the cap you can attach the vacuum cleaner wand to with the adhesive tape.

Now here's how to use it: turn the vacuum cleaner on and place your fashioned hood over the screw. The suction may keep it in place, or you may need a helper or duct tape. Now stick your moto-tool in the top of the hood and grind away. Hopefully, the vacuum cleaner will suck away the filings well enough to prevent damage to the motherboard.

Here's another thought: if you can access the edge of the motherboard, you might be able to get a hacksaw blade between the mobo and the case and cut the offending standoff off.

Screw Extractor

[adamy]

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.

Re:Screw Extractor

[Polo]

Another thing missing is the use of explosives. By using a carefully designed charge, it should be possible to neatly shear off the screw.

For instance, the space shuttle actually doesn't rise off the pad until some explosive charges shear some bolts that let it come free of the ground.

The same technique should be applied here.

Thank you.

Drill once, then use a screw extractor

[Anonymous Coward]

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/

It's a complicated process, but it should work...

[jpsst34]

Here's what you'll need:

One tube of KY Jelly

One large drill press

One buffalo - live or stuffed, preferably stuffed, for safety's sake

One seven layer burrito

Two female midgets, preferably with experience in adult films

One hand drill or dremmel moto-tool

One 1-2 mm drill bit

3.25 pounds of hashish

One set of rubber sheets

What to do:

Use the hand drill or dremmel coupled with the small bit to drill the center of the screw away. Next, gather the sex jelly, drill press, buffalo, seven layer burrito, midgets, hash, and sheets and have fun celebrating your newly freed motherboard.

The obvious and simplest method

[Crash Gordon]

I'm surprised nobody else has suggested this:

Find the idiot who cross-threaded the screw to begin with, and explain to them that their life depends on their ability to remove that screw without damaging the motherboard.

Then leave them alone while they solve the problem for you. This is a forward-looking solution, as it not only fixes the current problem but also reduces the likelihood of future problems.

Re:The obvious and simplest method

[JediTrainer]

Find the idiot who cross-threaded the screw to begin with, and explain to them that their life depends on their ability to remove that screw without damaging the motherboard.

Who do you think posted the question to Ask Slashdot in the first place?

Cross-threaded, or Stripped?

[Euphonious Coward]

There's usually nothing to prevent just unscrewing a cross-threaded screw. You just turn it and it comes out. The standoff would be damaged, then, and you'd want to replace it if you could. If you can't get at the screw on the other end, though, that's hard.

What the poster may mean is that the screw head itself is stripped out. Most of the suggestions above seem to relate to drilling out a stripped screw head.

I said "usually", above. Sometimes, if it's cross-threaded, then when you try to unscrew it, you end up turning the screw and the standoff, and unscrewing the standoff from the screw on the other end. If the other-end screw is (or gets) loose, all three turn freely, and you get nowhere. Even drilling might not help, because the bit just spins the whole assembly.

If this is what really happened, the only solution is to get a grip on either the standoff or the screwhead. If you manage the former, you can just unscrew it. If only the latter (e.g. with a vise-grip) then you can drill it out. You might want to super-glue the other end of standoff into place afterward, if you can't tighten that side's screw.

In general, you should post a more precise description of your problem if you hope to get helpful answers.

Re:The mechanic's friend

[sporktoast]

I recall using Superglue once in just such a situation. I had an old XT box and I wanted to shoehorn a 286 into it. The old mobo had a mounting screw that I'd managed to strip and couldn't get out to save my life. I thought about drilling it, but a friend suggested the Superglue route. I went to the hardware store and found a cheap-but-sturdy-enough nutdriver. I glued it into place, waited extra long for it to set and just removed it all together. If I'd been feeling extra thrifty (or pessimistic about possible repeat circumstances), I might have used some nail polish remover and salvaged the nut driver.

I had considered the Vise-Grip method, but even the needle-nosed models were still a bit bulky for that particular tight spot.

Re:Zen

[clintp]

The relevant passage

The first [negative aspects of traditional approaches to producing Quality] is stuckness, a mental stuckness that accompanies the physical stuckness of whatever it is you're working on. The same thing Chris was suffering from. A screw sticks, for example, on a side cover assembly. You check the manual to see if there might be any special cause for this screw to come off so hard, but all it says is ``Remove side cover plate'' in that wonderful terse technical style that never tells you what you want to know. There's no earlier procedure left undone that might cause the cover screws to stick.

If you're experienced you'd probably apply a penetrating liquid and an impact driver at this point. But suppose you're inexperienced and you attach a self-locking plier wrench to the shank of your screwdriver and really twist it hard, a procedure you've had success with in the past, but which this time succeeds only in tearing the slot of the screw.

Your mind was already thinking ahead to what you would do when the cover plate was off, and so it takes a little time to realize that this irritating minor annoyance of a torn screw slot isn't just irritating and minor. You're stuck. Stopped. Terminated. It's absolutely stopped you from fixing the motorcycle.

This isn't a rare scene in science or technology. This is the commonest scene of all. Just plain stuck. In traditional maintenance this is the worst of all moments, so bad that you have avoided even thinking about it before you come to it.

The book's no good to you now. Neither is scientific reason. You don't need any scientific experiments to find out what's wrong. It's obvious what's wrong. What you need is an hypothesis for how you're going to get that slotless screw out of there and scientific method doesn't provide any of these hypotheses. It operates only after they're around.

This is the zero moment of consciousness. Stuck. No answer. Honked. Kaput. It's a miserable experience emotionally. You're losing time. You're incompetent. You don't know what you're doing. You should be ashamed of yourself. You should take the machine to a real mechanic who knows how to figure these things out.

It's normal at this point for the fear-anger syndrome to take over and make you want to hammer on that side plate with a chisel, to pound it off with a sledge if necessary. You think about it, and the more you think about it the more you're inclined to take the whole machine to a high bridge and drop it off. It's just outrageous that a tiny little slot of a screw can defeat you so totally.

What you're up against is the great unknown, the void of all Western thought. You need some ideas, some hypotheses. Traditional scientific method, unfortunately, has never quite gotten around to say exactly where to pick up more of these hypotheses. Traditional scientific method has always been at the very best, 20-20 hindsight. It's good for seeing where you've been. It's good for testing the truth of what you think you know, but it can't tell you where you ought to go, unless where you ought to go is a continuation of where you were going in the past. Creativity, originality, inventiveness, intuition, imagination...``unstuckness,'' in other words...are completely outside its domain. [...]

My favorite portion of ensuing discussion about the limits of the scientific method and some traditional modes of thought is the statement that

[...] as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out.

.

Excellent book, every programmer should read it. At least to be able to laugh when their boss uses the word "Quality". :)

Re:The mechanic's friend

[n9hmg]

Instead of superglue, clean the head... In such circumstances, I just use 70% isopropanol. It's a good solvent for hydrophobic and hydrophilic contaminants, and any leftover dries really clean. Spritz an appropriate-sized philips-head screwdriver head with silicon lubricant. Mix up a little JB-Weld, and work a drop into the head with a toothpick to ensure that it is contacting as much as possible. Set another drop on top of that one and stick your slicked-up screwdriver bit into it - secure with something... I like the little radioshack extra-hands jig thingy. GO AWAY, and leave it alone for a whole day. Then, turn the screwdriver bit. The head WILL turn with it. I can't vouch for the shank. If the shank stays, you'll have to drill it out, or perhaps just do without that mounting point? If you drill it out, be very careful to remove only enough to get a tap in there to clean the threads... you'll probably have to go up one size, as you're unlikely to get it perfectly down the center. Keep a vacuum on the drillpoint to avoid deadly metal slivers.
On larger screws/bolts/studs, I like to get some heavy-walled steel pipe with an I.D. just slightly smaller than the head. Set that on the head, and weld a bead around the inside joint. Take a big old 36-inch Rigid pipe wrench, put a pipe on it if necessary, and move it. I did that once on the upper balljoint on a Dodge dart. It actually took the threads right out of the upper control arm - smooth as if it were machined. Phyrric victory, but I won.

Re:Drill it out --- Mod up as FUNNY

[shepd]

Umm, you do realise that magnets generally don't damage computer electronics apart from magnetic storage and CRTs, right? I'm sure you could find an odd case of something else they destroy (Floppy read heads?) but AFAIK, none of that will be soldered onto the motherboard.

Re:Drill it out (metal shavings)

[littlerubberfeet]

You are doing surgery, approach it as such. Get some thin nylon cloth and use a hole punch or something similar to make a small hole large enough to fit the screw head.

Put the cloth on the motherboard, with the hole centered on the screw. Press it down so that the cloth is below the level of the screw. Drill away, using increasingly larger bits. When removing the cloth, put your finger on the hole. With the other hand, pick up the edges of the cloth, using your finger to seal the hole.

Good Luck