Another quick and easy method that I used in the old tool and die days: lock two nuts together on a bolt. spin them into a bench grinder to produce a 30 degree chamfer on one of them (careful to leave enough to get a socket on). Now chamfer the hole through which the mirror stud will protrude. The newly tapered nut will drop into this chamfered hole like an ice cream cone, allowing the threads to grab what little bit of stud is protruding. You just bought yourself 1/8-3/16 worth of threads that you didn't have before. Take the two nuts back off the stud, and use the new chamfered nut to mount up your mirror.
Gary (I'm a retired machinist)
darksider #44
Think I'll add this in here as well... which I just posted elsewhere on this forum:
Security nuts/bolts 101.
Here's what ya do:
Buy some button head machine screws...
They can't be removed with anything but an allen wrench. Then fill the hole after ya put em on. Or get some plain old stainless steel allen headed cap screws, chuck them up in your cordless drill (not too tight... don't wanna mess up the threads) and grind the heads on your bench grinder so that they're round. Vise grips can't grab them. Mount up your lights. Then simply fill the allen heads with a little Bondo. You can pick it out easy enough if you ever want to take them off. Otherwise you could just use clay or some well chewed gum. Either way, the thieves won't be able to get an allen wrench in the hole, and thy won't think to check to see why. Oh, and if you're using a bolt and nut, put a little grease under the head of the bolt so it'll spin if the thief tries to simply turn the nut.
Or you can try these barrel nuts:
CLICKY
They look like this:
You can fill in the head once it's installed just like I described above.
Or you can spend some money and get these security nuts: they're pricey, but they're amazing. Do not use lock washers.
CLICKY
Keep in mind that if a crook wants em bad enough, there's nothing you can do. A battery powered Dremel and/or sawzall is standard equipment in the tool bag of too many modern day thieves. That kind of equipment can make short work of any security measures you might use.