Permanently locking an m3 screw

[jdennings]

For the mechanically inclined out there: I have a couple small steel m3 screws that partially backed out of a piece of aluminum after a mild crash/very rough landing. There is still some friction left (it won't pull out, still needs to be turned) but I suspect most of the female threads in the aluminum block are worn, and I can't achieve a tight lock. I've been thinking of gluing the screws back permanently (that's ok, I don't need to have them removable) with either red threadlocker or JB Weld. Would one be better than the other, or are there better alternatives? (short of re-threading with an insert)?

Also, can I expect to get the same sort of joint strength after gluing? Length of screw in material is short, about 5mm. Thanks for any advice.

 

[Aerialmediaone]

I would tap the hole to the next size up and use a larger screw if possible.


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[Motopreserve]

If you're not afraid of permanent - JB Weld would probably be best. The red thread locker would want more thread to grip to.

You may be able to tap it to 4mm of you ever need to remove the bolts.

EDIT: aerial media beat me to it

 

[jdennings]

Thanks. I can't use a larger screw, I've got to use the existing one because the screw is part of a cam. I'll try JB Weld first, I was sort of thinking the same thing about threadlocker and its requirement for good threads. If this doesn't work I'll drill, thread and try one of these inserts, don't really know if these exist for m3.

 

[Motopreserve]

I'm sure they exist - but I've always found them to be a PITA. I think JB Weld will hold - can't imagine anything on an MR will have more force than its capable of.

Just make sure you mix it well.

 

[Old Man]

Thanks. I can't use a larger screw, I've got to use the existing one because the screw is part of a cam. I'll try JB Weld first, I was sort of thinking the same thing about threadlocker and its requirement for good threads. If this doesn't work I'll drill, thread and try one of these inserts, don't really know if these exist for m3.

M3 Helicoils DO exist but they always have to be ordered. Nobody stocks them on local shelves. Www.mcmaster.com. Check the pitch. It will be .5 or .6. You cannot use one with the other.


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[jdennings]

Great to know, thanks O.M. So far so good with JB Weld, but I think I'm gonna go with Helicoils ultimately ...