Torquing nuts (!)

[Uncle Pauly]

So… without wanting to over-complicate what is probably a very simple matter… I’ve recently found myself wondering how much torque can be applied to a typical barrel nut - in my case when fitting a floating hand guard. I don't mean how much measurable torque in Nm, more a question of "how tight is tight enough - or too tight?"

 

Reason I’m asking is because I’ve just recently fitted a MK16 handguard to a GBB (TM MWS). Barrel nut is this type…

…which I tightened using a C-spanner, like the one below (gently tapping the wrench arm with a hammer, whilst the upper receiver was held in place using an AR vice block).

 

All good. Only there’s a gap of just <1mm between the rail and receiver, which I reckon could be closed by cranking the barrel nut a little further. However, it’s already been tightened using a hammer to apply extra torque, as mentioned, and I don’t want to over-do it and wreck the threads.

 

So... does anyone have any tips for torquing their nuts!?

 

 

…or it is just a case of case of playing it by ear, so to speak, and continuing to crank until things don’t want to budge any further? I'm firmly in this camp at the moment, but wanted to check whether there's a smarter way of going about this.

 

Cheers 🍺

[Chev Chelios]

You sure its not bottoming out? If its not just keep taking it off and on again cleaning and lubing the threads as you go. 

 

I would not like to guess at how much torque the thread could take without knowing the composite of the alu and how deep the threads are cut.

[Shamal]

I was always told "tighten them till they squeak " lol

Regards 

[Adolf Hamster]

without a torque wrench it's the kind of thing you really have to do on feel.

 

and i really can't describe how to do it properly it's just one of those skills you pick up from years of doing it wrong.

[Tommikka]

If you want to be sure it’s not going to work loose then a drop of light duty threadlocker will hold it in place.

 

Be careful what strength is used as high strength thread lock needs heat and brute force to release, mid strength needs brute force and low strength needs some force.

 

Something like Loctite 222 will give a low strength fix 

[alxndrhll]

Agree with everything said so far, just remember this very valuable question... "Will I ever be able to undo this without potentially breaking something?".

If you suspect the answer is ever anything other than 'yes', stop.

Out of curiousity, are you using an AR block or similar to hold everything in place?

[Uncle Pauly]

5 hours ago, Chev Chelios said:

You sure its not bottoming out? If its not just keep taking it off and on again cleaning and lubing the threads as you go. 

Good question. I’m almost certain it’s not bottoming out - I think there’s still some thread left to play with - but am cautious not to push it too far! Both nut and receiver thread were lubed with a Teflon spray before assembly.
 

4 hours ago, Shamal said:

I was always told "tighten them till they squeak " lol

Regards 

You, sir, are a man of science and I salute you! 😁
 

4 hours ago, Adolf Hamster said:

without a torque wrench it's the kind of thing you really have to do on feel... it's just one of those skills you pick up from years of doing it wrong.

Hah! Funnily enough I totally get what you mean here. My other hobby is fixing up guitars and there’s plenty of ‘feel’ involved in that too.  Point noted 👍
 

3 hours ago, Tommikka said:

If you want to be sure it’s not going to work loose then a drop of light duty threadlocker will hold it in place.

Thanks, that’s a good call.
 

1 hour ago, alxndrhll said:

Agree with everything said so far, just remember this very valuable question... "Will I ever be able to undo this without potentially breaking something?".

If you suspect the answer is ever anything other than 'yes', stop.

Out of curiousity, are you using an AR block or similar to hold everything in place?

That’s some sensible reasoning 🙂 Yes, I’m still in the ‘safe zone’ of being able to undo the nut. It’s not crazy tight, I’m just being over-cautious with the parts being aluminum and not steel (and I’m not accustomed to working with aluminium). Yeah, I’m using an AR block and vice to hold the upper receiver. Makes the task much easier!

 

——-

 

Thanks to you all for the input here, appreciated! I’m probably going to err on the side of caution and not torque the nut any further. The hand guard is currently very sturdy once fitted - no wobble etc - just a slight gap as mentioned (<1mm). I can live with that for the sake of avoiding a Hulk Smash moment and wrecking stuff... and I’m quite prone to such moments 😬

 

Cheers all 🍺