Copperslip on nyloc nuts?

[amulheirn]

Gerry's manual states fairly clearly that copper slip should be used on all nuts in the build - presumably this is so that your torque reading is not affected by the dry surfaces of the threads.

I get that for bolts in the engine, particularly exhaust header bolts, but what do you do when the nut is a nyloc one? His manual also says that the friction provided by the nylon provides only a small part of their function - actually the main reason the nyloc works is because the metal of the nut and bolt thread surfaces are forced into closer contact by the nylon insert. But I still can't get over the feeling that lubricating something that I really don't want to come undone is a bad thing to do! Wondered what the opinion is on this?

Cheers,

A.

[Paul Blore]

Hi Andy,

I'm struggling to understand how/why the nylon insert would make the surfaces of the nut and bolt tighter. Surely, the simple fact that they've been tightened up does all of that.

Paul

[StewbieC]

I followed the manual and mine haven't worked loose. I put a paint pen line on the nut and mating surface and I give them a quick check once in a while. nothing budged.

[Roger King]

For engine component assembly, I use engine assembly lubricant or a spot of engine oil (ideally SAE30, but that's getting a bit fussy). ARP threads, for example, are best assembled using ARP's own assembly lubricant.
Copperslip is best used for heavy chassis components, some bushings (spacers, not bearings), and dissimilar metals. I wouldn't use it routinely on Nylocs.

Paul, just saw your response - the Nylon has a memory and exerts a radial grip on the thread which the nut cannot do. Same kind of principle as Aerotights and other locking nuts. It will be in closer contact because it acts as a 'brake' on the nut, making it harder to wind down the thread against the thrust side of the male thread.
Very few Nylocs on my car! Always been a fan of spring washers, personally, founder member of the dinosaurs' club

[amulheirn]

Great advice as always - thanks everyone...

[catsx11]

.

[Paul Blore]

Hi Roger,

I understand what a Nyloc nut is, my question was more regarding the idea that the Nyloc bit increased the metal to metal force. If the nut is correctly torque'd down, surely the Nyloc element isn't doing anything. It only comes into play if the nut comes loose. The torque required to overcome the friction imposed by the Nyloc element will be far less than the required torque setting for the nut......surely?

Paul

[peterc]

Personally I would never use any lubricant on a nyloc nut on the basis that you want the nylon to grip properly not increase its ability to move.
I only use copper slip on potentially hot items and those won't be using nylocs.

One assumes that it's the concern of potential vibration that might loosen the nut thus requiring a self locking nut.
Sensitive or critical connections should have a castlated nut and split pin or second choice would be using a shake proof washer.
Cylinder head bolts and other connections where zero movement can be tolerated use the underside of their head to maintain their position and tightness but need lubricant on the thread to ensure correct torque is achieved.

But we have strayed from the original question which is simply answered by no don't use copper grease or anything similar.
Peter C

[amulheirn]

I'm struggling to understand how/why the nylon insert would make the surfaces of the nut and bolt tighter. Surely, the simple fact that they've been tightened up does all of that.

I suppose so - I was just referencing Gerry's manual advice really. Not sure of the physics of it myself.

My question stems from thinking about the U-bolts holding springs to the axle - there's a rubber spring pad there, so obviously no torqueing it down to a particular spec due to the compressibility of the rubber. So there are three issues really: 1 - how tight is tight enough, 2- how to stop the nut from unwinding when subjected to vibration and 3, whether to use any lube at all.

I think the answer to 2 and 3 is probably (as PeterC and Roger say) to use a nyloc or aerotight (I think these have other names too) and no lube.

My answer to 1 (failing to find an answer in either the Haynes or MGB workshop manuals) was 'pretty tight', but not 'mega-bastard tight'.

Thanks again...
A.

[peterc]

Surprised the Haynes manual didn't help. I would have expected there to be loads of members with MGB set ups or ask Gerry for a torque setting.
You should use a torque setting for uniformity, its just that the torque figure will be low enough not to overly squash the rubber gasket.

I happen to have an old Ford issued dealer maintenance manual for a 1968 Cortina which suggests the following settings in case its any help.
Rear spring U bolts = 20-25ft/lbs
Rear spring front hanger = 25-30 ft/lbs
Rear Spring shackle nuts = 12-15ft/lbs

Obviously I don't know the relative bolt sizes compared to the MGB set up but doubt its much different.
Suggest trying 10 ft/lbs and gradually increasing until you see the gasket start to squash.
Peter C