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Does tightening a bolt loosen it?

2K views 13 replies 11 participants last post by  Pirate650 
#1 ·
Before a big trip, it is always good to go over your bike and check for loose bolts and attachments. I usually go over bolts with my fingers checking if they are loose, but do not use a wrench on them unless I am suspicious of something or it's obvious.

My thought is, if a bolt is set tight from factory, it may have blue loctite on it, or not, but if you crank on it a little to check if it's tight, is it possible you might break that bond and actually cause the bolt to come out later?
 
#2 ·
Loctite should never "set" the way a glue does. It should constantly provide a friction high enough to prevent vibration from loosening the fastener.
Ideally it remains pliable in the threads.
 
#3 ·
"Loctite" and other thread locking products are cyanoacrylate adhesive that set in the absence of oxygen. Yes they do set, they do not remain pliable.

If you crank on a bolt you will, at the least lessen its hold.

A bigger problem is going to be the fact that you are cranking on a bolt that is already at its correct torque. very possibly, if not probably, overtightening in the process.

Tom R
 
#8 ·
Maybe the better bet would be to try to loosen the bolt with somewhat less torque than the specified tightening torque. If it doesn't move, you're fine. If it moves, probably need to remove it, clean it, put on the thread locker, and tighten to the specified torque.
I tend to try and tighten a bolt but with less than required torque. If it moves at all it is time for new loctite and the torque wrench. Probably not much difference in results.
 
#6 ·
I clean threads using a wire wheel in an electric drill or a wire brush.
as an aside- for rusty,severly clogged and or mildly damaged threads you can either use a die nut (which most probably wont have) or if you take a suitable nut and cut across it 3 times - opposite flat face to opposite flat face ,cut about 1/3rd the way down.This will make a "castellated" nut which is a cheap and very effective thread cleaner/reclaimer ;)
https://www.google.com.au/search?q=...a-Dyv4kYM:&usg=__uWDop_lSAO69SCQxW9ecgK5C5dU=

your home made job will have very narrow castellations but will work just fine ;)
 
#13 ·
A trick that I learned when I used to fly ultralight aircraft, is any time you tighten a bolt to a torque spec and want to be able to inspect that it remains at spec, use red nail polish and mark the bolt head to the surface.

That way it is very easy to inspect if anything has loosened -- the nail polish will be cracked.
 
#14 · (Edited)
YEP. I was an aircraft mechanic for 30 years before I wised up and got a real job. We used Torque Seal all the time on flight-critical systems, etc. Nail polish works great, too.

Torque Seal Anti-Sabotage Lacquer - Chief Aircraft Inc.

Some engine manufacturers call out a bolt-stretch spec for their connecting rod bolts. Measure it, stretch it a specified amount. Stretch it too much, toss it and try a new one.

When I check for bolt security, I turn it in the tightening direction, but not so much that it moves. If it moves, it was loose.
 
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