MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - torque settings and nyloc nuts

This is a bit of a basic question. I ordered some new rocker pillar studs and nuts for my engine rebuild and when I picked them up found the nuts were nyloc nuts. My parts manual shows plain nuts. Can I safely torque down nyloc nuts using the standard 25ft lbs or will the nyloc bit give me a false reading. Am I better off using plain nuts (with or without a locking washer?)?

Chris, normally plain nuts.
Chris H (1970 Midget 1275)

I have always used the same torque value.

But, to be totally sure, it is easy to find out: take a new nut and run it along the thread of the stud with your torque wrench. Use whatever that "free" torque value was as the amount you need to add to your value when torquing it for real.

And, of course, always throw away nyloc nuts after one use.


Norm
Norm Kerr

You DON'T have to throw away nylock nuts after one use. It's worth checking the nylon insert each time you re-use them. However, you are more likely to want to replace the nut because the flanks are damaged or rusty long before the nylon insert is worn to the point of being useless.

Anything is better then a spring washer or a lock tab.

There are books with this stuff in - by the late Carrol Smith.
Daniel Thirteen-Twelve

Re. Nyloc nuts.

Just a thought . . . . is it good practice to use Nyloc nuts on/inside an engine? Won't the engine temperatures and/or oil soften or destroy the nylon insert?

Andy Hock

that's interesting that you would say that, because the torque to remove a nyloc nut drops after each use, and the manufacturers recommend they not be re-used because this drop is difficult to predict.

They are so cheap, it seems like poor economy to re-use something designed for one-time use.


Norm
Norm Kerr

Hi Andy,

the typical max temp for a nylock nut is 250F, so should be fine inside of an engine, since the oil temperature is designed to be somewhere between 200 and 240F (above 240F, the oil starts to break down).


Norm
Norm Kerr

So how much does the torque required to removed to remove a nylock nut vary each time it's re-used? How do you know if you've never used them again? And for anyone else was their torque wrench checked for calibration between tests?

Is there a link to more than one manufacturer where they say do not use ours or any other manufacturers nylock nuts more than once.
Daniel Thirteen-Twelve

I always use new nylocs on critical fastenings - at least I do when I have new ones available. But the used ones always get re-cyled as there are always plenty of less critical places to use them. I thought that the nyloc insert was more to do with damping out vibrations that might loosen a nut - particularly if subject to twisting between components - than to add any significant torque resistance to undoing.
Guy Oneandahalf Sprites

Like Andy, I wouldn't use nylocks on the inside of an engine. Even if Norm's figures are correct, that's not enough margin to make me comfortable.

There are lock nuts that have no nylon. The are crushed to slightly oval on one end, and are all metal. I think they would be more appropriate.

Charley
C R Huff

>>Anything is better then a spring washer or a lock tab.<<

Interesting you should say that Daniel as I've often thought how much easier it would be to use a nyloc instead of trying to get a waher, split washer and nut on in some places

Can I always use nylocs instead of plain nut and spring washer?

I assume the use of a plain washer with a nyloc is usually a good idea

(I never touch anything that has a lock tab that would be dangerous for me and others!)
Nigel Atkins

As has been said, nyloc inserts are only there to resist undoing. As such, I will always re-use them as once a thread is cut in it, the effect is lessened. And since I don't know by how much, and given how cheap a new box of them is, I treat them as one use items.

For anything else, plain nuts and washers are usually fitted.
S Overy

Hi, you guys raise a really good question.

regarding using lock washers, or nylock nuts: is one better than the other?

I agree with Daniel, that thread locking is dependable, and lock washers really are not.

There has been an industry trend away from using lock washers (and "knurled face" nuts), toward more positive, thread locking means, like lock-tite on the threads, or inserted nylon "plugs" in the bolt threads, or prevailing threads that are locally distorted on the bolt, or deformed nuts, or nylock nuts.

Modern cars use some kind of thread locking in critical areas, and nothing at all in non-critical areas. The design of a properly torqued joint prevents their need for non-critical joints, and for the critical joints, they are used as insurance. I have also seen a trend away from using knurled face nuts (the line-worker friendly attempt at replacing the lock washer) in non-critical joints to smooth face nuts (cheaper to make, and same durability performance). Testing I have seen has shown that when locking is necessary, the lock washer, or a knurled face nut, simply didn't provide any protection (about 1 Nm, or so, is what the testing I saw concluded, which is a little less than finger tight), where thread locking worked very well, every time.


I wouldn't be surprised if you could safely eliminate all the lock washers from a midget, and nothing would come loose. However, if any of the bolts were over-torqued by a DPO, stretching them beyond their proof load, making them worthless, the presence of a lock washer wouldn't make much difference either way.


But I keep on using the lock washers in my car just because they can't do any harm, and even if they probably don't do any good either, are part of the "charm" of working on an old car.


Norm
Norm Kerr

I have often seen split lock washers used in addition to a plain washer. That surely cannot be right? The stepped edge of the spring washer must be designed to dig into the mating surfaces, but if one of these is a plain washer that is theoretically free to move anyway, then what is the good of that!

I don't trust them, and yet they were the industry standard for a century or more.
Guy Oneandahalf Sprites

Nuts, bolts, fasteners and plumbing handbook by Carroll Smith ISBN 0-87938-406-9

Nigel, on my car there are no spring washers and no lock tabs - everytime I found one I threw it away. The car is holding together so far.
Daniel Thirteen-Twelve

Cheers Daniel, good news for me on nyloc use especialy as I have to remove and replace the four sets of nuts and bolts that hold the top of the rad grille it - my figers are too short and fat and it's always the last plain and split washers that drop inside out of sight

That is a place where you need plain and split combination as the locating holes are slightly oversized and elongated so the split washer could sit in the hole part
Nigel Atkins

Im with charley...use nylocs on suspension and other areas but not inside an engine

is there such a thing as grade 8 and grade 5 nylocs???

seriously I really dont know.

prop
Prop

On the subject of measuring the running torque of a nylock nut and adding it to the final torque used to be the standard on SUBSAFE items on nuclear submarines. A few years before I retired, that requirement was dropped as it was found that the running torque was such a small part of the final torque, that is was a waste of time to make the measurement and do the math. Cheers - Dave
David DuBois

The official workshop manual lists the torque for nyloc nuts on big-ends at 32-34 lb-ft, that's pretty close to the inside of the engine and official endorsement I would say.
Paul Walbran

We have moved on to Philidas nuts for conrods in A series engines as we feel they are better than Nyloc... a word of warning though...Philidas nuts, when rusty (eg suspension use) do not like to come undone!!!

http://www.philidasfasteners.co.uk/aboutphilidas.html

Peter
P Burgess

So when you say the manueal says its okay to use nylocs on the big ends 32 - 34 ft lbs.... You dont mean the garden varity of nylocs in the genral bins of the local tractor supply company, menards, Ace hardware or true value home hardware store im guessing...

your talking about a nyloc with special specs, is that correct ?

Cause the local general nylocs hardware are like 25 to 50 cents each compared to about $100 for ARP hardware for big ends

Am I missing something in the translation
Prop

Re Grade 5 or 5 as far as I recall this refers ro the Strength of the nut & thus the torque which can be applied. The Nyloc (or doubtless Chinese equivalent!) is there simply to retain the torque & has no infuence on the Tightening torque. The advantage of the Nylon(or whatever plastic) insert is that it does not damage the threads -unlike some other prevailing torque nuts which - if you use them often enough will wear the thread down leaving no locking & less thread! Remember the nut is invariably stronger than the bolt & it will be the bolt thread that strips first!
This has afdded some smoke to the discussion & I am sure someone will say I'm wrong! Personally I would not be keen on Nylocs inside the engine on reciprocating bits!!
DG Harrison

when I started racing the Midget one big decision I made was to buy in the engines from a reputable builder; boy am I glad, so much less to fret and worry over. I don't know what's inside but they haven't fallen apart yet :-)
David Smith

Hey David,

i think this converstion is more of an intresting curiosity of what is possiable then making a decision as to which way to go
Prop

Peter - do you mean their turret nuts?
Daniel Thirteen-Twelve

Doesn't happen too often but got to agree with David

I know of absolutely no benefit in building your own engine however I can name a dozen good reasons for entrusting the work to an expert who builds engines every day of the week.

Whilst I tell my builder what spec he needs to build in the engine builder does all the machining all the parts sourcing and all the putting together.

Peace of mind is priceless.
Robert (Bob) Midget Turbo

Hi Daniel

I guess those are the ones as we use the Rail recommended ones.

Peter
P Burgess

This thread was discussed between 17/12/2010 and 21/12/2010

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.