How to stop bolts from loosening

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Gary E

Veteran
Location
Hampshire
Hard to tell from the link but does that clamp have a bolt going in from both sides on the clamp? is it threaded?

My point is, if so, why not just put a drill straight through from one side to the other and then fit a longer Bolt with a Nyloc (or Thread-Loc or Castellated Nut and Split pin etc.)?
 

Ajax Bay

Guru
Location
East Devon
Hard to tell from the link but does that clamp have a bolt going in from both sides on the clamp? is it threaded?
Pretty sure that there are 2 'bosses' threaded through, with a small gap between (don't know if holes align), too small for a nyloc nut to be placed in there, let alone two. If the holes align you could run one (longer) bolt through and use a nut, but the gap might cause some flex in use with consequent lack of security.
 
OP
OP
BurningLegs

BurningLegs

Veteran
My point is, if so, why not just put a drill straight through from one side to the other and then fit a longer Bolt with a Nyloc (or Thread-Loc or Castellated Nut and Split pin etc.)?

This is a better image:
MPART_SEAT_CLAMP_RACKT.jpg


So there is a small gap between the two threaded sides, but the gap is not big enough to fit a nut (or two).

Right now, I have one M5 bolt threaded into each side of the fitting, and a washer. I suppose it isn't particularly surprising that it is working loose!

I'm considering picking this up from my local Halfords:
http://www.halfords.com/motoring/paints-body-repair/adhesives/loctite-threadlocker

It essentially seems to be a "pritt stick" type product that you smear onto the thread. Is this the right product? I don't want to use something too strong that could prevent me from removing the bolts in the future, because I do remove the rack from time to time.

When using that product - am I right to think that it should be applied around the entire thread along the last few mm of the bolt? Or should it be literally all over the thread?
 

Ajax Bay

Guru
Location
East Devon
Yes - correct product (though see this link - much cheaper). Threadlocker needs to be applied to the section of the bolt that's going to be 'in' the threaded hole (but 4mm will do the job). You will not have any problem unscrewing the bolt if and when you need to: that's a feature of threadlocker: its force can be broken by the torque you apply.
 
Last edited:

Gary E

Veteran
Location
Hampshire
This is a better image:
View attachment 379179

So there is a small gap between the two threaded sides, but the gap is not big enough to fit a nut (or two).

Right now, I have one M5 bolt threaded into each side of the fitting, and a washer. I suppose it isn't particularly surprising that it is working loose!

I'm considering picking this up from my local Halfords:
http://www.halfords.com/motoring/paints-body-repair/adhesives/loctite-threadlocker

It essentially seems to be a "pritt stick" type product that you smear onto the thread. Is this the right product? I don't want to use something too strong that could prevent me from removing the bolts in the future, because I do remove the rack from time to time.

When using that product - am I right to think that it should be applied around the entire thread along the last few mm of the bolt? Or should it be literally all over the thread?
I think I'd be tempted just to drill straight through and fit a single long Bolt. The Bolt will only be taking a shear load so it wouldn't need to be tightened beyond the point where there was no axial play, once fitted with a stiff-nut of some sort it'll be going nowhere :smile:
 

Profpointy

Legendary Member
There are many grades of threadlocker. "low strength" is what you want here. Loctite, a leading brand, have data sheets to guide you through their myriad set of products, each with a code number and various attributes such as chemical or heat resistance, but conveniently also say "low strenght", "medium strenght" etc on the bottle. The higher strenghts aren't intended to be undone ever, so don't just think higher strenght is better !
 
OP
OP
BurningLegs

BurningLegs

Veteran
Yes - correct product (though see this link - much cheaper). Threadlocker needs to be applied to the section of the bolt that's going to be 'in' the threaded hole (but 4mm will do the job). You will not have any problem unscrewing the bolt if and when you need to: that's a feature of threadlocker: its force can be broken by the torque you apply.

Thanks for this link, I missed it at first!

For now I have spent less than £1 on some split washers from Toolstation and will see how I get on with those. If the bolts still work themselves loose I will get some of the thread lock you linked to. I’ve got my fingers crossed that the split washers alone will do it for almost no cost!

Thanks for the input everyone, very much appreciated. :okay::cheers:
 

flake99please

We all scream for ice cream
Location
Edinburgh
Can you show us what is the other side of this clamp? What does the bolt in question, bolt into? Is there a nut on the other side, or does the bolt screw into threaded plastic?
 

Ajax Bay

Guru
Location
East Devon
What does the bolt in question, bolt into? Is there a nut on the other side, or does the bolt screw into threaded plastic?
This is a replacement (metal) seatclamp, designed to secure the seat post in position. Your bike will likely have one - have a look. Have you looked at the link in post#9?
The main culprits are the bolts that screw into my seat post clamp (one of THESE).
The OP's rack supports bolt onto the 2 lower bosses. These are the bolts that are vibrating loose.
 
OP
OP
BurningLegs

BurningLegs

Veteran
Can you show us what is the other side of this clamp? What does the bolt in question, bolt into? Is there a nut on the other side, or does the bolt screw into threaded plastic?

Hi Flake. As @Ajax Bay mentioned - this is a metal component and the other side looks the same as the side in this photo, to be honest. It's a seat post clamp that has the extra eyelets/bosses on the bottom for mounting a pannier rack. These are quite commonly used on bikes that do not have rack mounts on the frame, which is the case for my frame. I don't have any issue with the bolt that clamps the seat post, just the two that I use to mount my rack (one either side).

When the rack mount bolts are attached there are no nuts involved, the holes you can see are threaded all the way through and the bolts just about reach the end of the thread but do not come out into the gap between the two eyelets.
 
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