Nut keeps falling off of bolt
May 31, 2012 6:45 AM   Subscribe

How can I make these nuts and bolts stay put?

I've used bolts like so to attach a keyboard tray to my desk. The bottom nuts keep falling off. How do I keep them fastened?
posted by morninj to Home & Garden (13 answers total)
Rubber gaskets?
posted by Ruthless Bunny at 6:47 AM on May 31, 2012

Use a lock washer or replace the nuts with nylock nuts.
posted by spikeleemajortomdickandharryconnickjrmints at 6:47 AM on May 31, 2012

Go down to Home Depot (or any hardware store) and get some Threadlock or a couple lock washers. Either one should do the trick.
posted by bondcliff at 6:47 AM on May 31, 2012

Metal washers or lock washers.
posted by Thorzdad at 6:48 AM on May 31, 2012

They make locking nuts with a nylon insert that are cheap. Grab some of them, or some lock washers and you should be good to go. I mounted the rack for my side cases on my motorcycle using these type of locking nuts, and if they can hold on a 125 hp motorcycle for the past two years and 30k miles without backing off they should be more than up to the task of staying put on a stationary desk.
posted by chosemerveilleux at 7:00 AM on May 31, 2012

I'd avoid the threadlock, if you ever want to actually unscrew the thing.

Go with a lock washer, or even throwing another nut on there next to it will help.
posted by Citrus at 7:00 AM on May 31, 2012

Best answer: Replace the lower nut with a nyloc (a nut with an integral nylon locking ring) is your best bet. After that, either threadlocking both nuts with Loctite or similar, then with a spring washer in order of effectiveness.

The nicer long term solution would be to get a sleeve made of steel or nylon to fit over the upper part of that thread and cut it to length so that it fills the entire threaded area (from where we can see, upwards out of shot to whatever is up there) and then clamp this with a nyloc below it. That way it won't come off at all.
posted by Brockles at 7:02 AM on May 31, 2012

Cheapest answer - double up the nuts (run down the first nut to tight, then jam the second nut against it.)
Next: lock washers.
Next: Nylon-insert stop nut.
Worst: locktite.
posted by notsnot at 7:03 AM on May 31, 2012

Keep in mind that Loctite comes in different grades. The 'blue' stuff is easily removable by hand. The 'red' stuff is nearly impossible to remove and you shouldn't use it. So, Loctite is fine if you get the right kind.
posted by Confess, Fletch at 7:11 AM on May 31, 2012 [2 favorites]

The 'blue' stuff is easily removable by hand. The 'red' stuff is nearly impossible to remove and you shouldn't use it.

Not strictly true. Red is only a little stronger than blue (in Loctite's colour system). Green is the strongest Loctite (bearing retainer) and is the nearly impossible one to get off unless you apply some direct heat (at which point it comes off really easily). Loctite is often misused and the amount of resistance to using it in this thread suggests that the majority of people don't understand either the different grades of thread locking liquids in terms of severity or don't understand that you need to change your method for removal if threadlocker is used.

Most loctite is not very resistant to direct heat. You can either use a heat gun or a small torch (from a MAP gas hand held from Home Depot to even those little torches they use in kitchens for Creme Brulee) and just heat the nut. Not cherry red or anything, but just hot enough that you can't really touch it and have to use the socket/tool or gloves to handle it. This will pretty easily break down the loctite and removal is then perfectly normal. The major issue with loctite is that either people don't realise it is on there before they try and undo the nut or they try and just force it off anyway. That way you can REALLY struggle getting things off but it isn't necessarily the fault of the thread locking stuff.
posted by Brockles at 7:34 AM on May 31, 2012

I think what gets people wound up about loctite is when they use it in a circumstance where one end has a screw head and the other a bolt. If they're not careful when trying to remove it - they use a motorized screwdriver and/or the wrong size head - the loctite is strong enough that they strip out the head and now it's a big issue.

This is preventable and, based on the above picture, not pertinent here (presuming you're not mis-using open-end adjustable wrenches) since you'll have a much easier time getting some torsion.
posted by phearlez at 8:08 AM on May 31, 2012

Cheapy-cheapest answer: small piece of electrical tape wrapped around the bottom nut.
posted by Benjy at 8:23 AM on May 31, 2012

In theory, if you tighten two nuts toward each other really hard on either side of a piece they're clamping, they should lock each other and the clamped piece together, and stay put. But I suspect that the stuff you're clamping between those two nuts is plastic, not metal, and that over time it's deforming under pressure just sufficiently to let the bottom nut unlock.

So you need to reduce the pressure on the plastic to discourage deformation, while maintaining the same tension in the threaded rod between the two nuts. You can do that by spreading the force you're applying to the plastic over a larger area, using a flat washer between each nut and the plastic.

Even so, the plastic will probably still creep a little over time. Putting spring washers between the nuts and the flat washers will allow for that while still maintaining enough tension to keep everything nice and tight.

Using nylock nuts instead of plain ones will certainly stop the nut from falling off once the plastic has flowed, though because these nuts don't expand like spring washers they will not grip the plastic as hard once it has started to creep.
posted by flabdablet at 9:43 AM on May 31, 2012

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