Nylock nuts

[GUtripper]

I run a spindle hub front end on the Tj, and the existing spindle studs (ie attaching the spindle to the outer axle C) are stretched and some threads stripped......

Have sourced some new studs from the USA, they have a knurled shaft that presses into the C from the inside..... However they are about 7mm shorter.

I have some nylock nuts to go on, but they just.....or maybe not quite sit flush with the end of the studs when torqued up tight. The previous studs being longer extended about 6/7 mm past the end of the nut.

Is this ok? Do nylock nuts need to be fully threaded onto a bolt/stud? At a guess the nylock/nylon part is about 4mm deep, they are 7/16 unf thread. Will it be ok, or loosen over time? Do I need to hunt around for longer studs?

Opinions?

[-Scott-]

I run a spindle hub front end on the Tj, and the existing spindle studs (ie attaching the spindle to the outer axle C) are stretched and some threads stripped......

Have sourced some new studs from the USA, they have a knurled shaft that presses into the C from the inside..... However they are about 7mm shorter.

I have some nylock nuts to go on, but they just.....or maybe not quite sit flush with the end of the studs when torqued up tight. The previous studs being longer extended about 6/7 mm past the end of the nut.

Is this ok? Do nylock nuts need to be fully threaded onto a bolt/stud? At a guess the nylock/nylon part is about 4mm deep, they are 7/16 unf thread. Will it be ok, or loosen over time? Do I need to hunt around for longer studs?

Opinions?

In my opinion, the nyloc nuts will only stop a loose nut vibrating off the stud - so the nut will still be on the studs that weren't tightened properly, and the snapped studs (if you can find them after they've snapped).

If the nuts are torqued up properly, and the stud thread protrudes well into the nylon section, I would be entirely happy.

[stilivn]

Thread locker, used it on a set of spotties once with nylocks and had to cut them off with a grinder.

[mkpatrol]

A general basic engineering requirement for all nuts is a minimum of 1.5 threads past the head of the nut surface. This was a guide we used to use when I worked on Cessna aircraft & is a rule I stick by.

If thy nycloc nut is flush then I would say you will not get the full benifit of the locking system as there is alway a slight taper at the start of the thread. I like to at least see 3 threads past the head of a nylock or metalock nut.

Basics of Aircraft Nut Installation

When using a castle nut, the cotter pin hole may not line up with the slots on the nut. The Mechanics General Handbook states "except in cases of highly stressed engine parts, the nut may be over tightened to permit lining up the next slot with the cotter pin hole." Common sense should prevail. Do not over tighten to an extreme, instead, remove the nut and use a different washer and then try to line the holes again.
A fiber nut may be reused if you are unable to tighten by hand.
At least one thread should be projecting past the fiber on a fiber nut installation.
No self-locking nuts on moving part installations.
Do not use AN364 or AN365 fiber nuts in areas of high temperature - above 250' F.
Shear nuts are to be used only in shear loads (not tension).
Plain nuts require a locking device such as a lockwasher or a check nut.
When using a lockwasher, place a plain washer between the surface of the airplane part and the lockwasher.
Shear nuts and standard nuts have different torque values.
Use wing nuts only where hand tightness is adequate.

http://exp-aircraft.com/library/alexande/hardware.html


This publication says 1 thread, we used to go on the 1.5 principle. This was a basic principle if there were no guiding instructions by the manufacturer of the aircraft.

[-Scott-]

A general basic engineering requirement for all nuts is a minimum of 1.5 threads past the head of the nut surface. This was a guide we used to use when I worked on Cessna aircraft & is a rule I stick by.

If thy nycloc nut is flush then I would say you will not get the full benifit of the locking system as there is alway a slight taper at the start of the thread. I like to at least see 3 threads past the head of a nylock or metalock nut.

Basics of Aircraft Nut Installation

When using a castle nut, the cotter pin hole may not line up with the slots on the nut. The Mechanics General Handbook states "except in cases of highly stressed engine parts, the nut may be over tightened to permit lining up the next slot with the cotter pin hole." Common sense should prevail. Do not over tighten to an extreme, instead, remove the nut and use a different washer and then try to line the holes again.
A fiber nut may be reused if you are unable to tighten by hand.
At least one thread should be projecting past the fiber on a fiber nut installation.
No self-locking nuts on moving part installations.
Do not use AN364 or AN365 fiber nuts in areas of high temperature - above 250' F.
Shear nuts are to be used only in shear loads (not tension).
Plain nuts require a locking device such as a lockwasher or a check nut.
When using a lockwasher, place a plain washer between the surface of the airplane part and the lockwasher.
Shear nuts and standard nuts have different torque values.
Use wing nuts only where hand tightness is adequate.

http://exp-aircraft.com/library/alexande/hardware.html


This publication says 1 thread, we used to go on the 1.5 principle. This was a basic principle if there were no guiding instructions by the manufacturer of the aircraft.

I see no mention of nyloc nuts.

The "1 thread" protrusion is to ensure that there is full engagement between nut and bolt. Saying "full engagement" or "flush" is too open to interpretation, so "1 thread past" provides a safety margin - any protrusion will do, anything less than full engagement is not acceptable.

The difference between "1 thread" and "0.1 thread" makes no difference to the strength of the joint if there is truly full engagement, so the "1 thread" isn't critical. "0.9 thread" isn't a disaster waiting to happen.

The nylon insert provides a vibration resistance / anti-rotation function, and is primarily useful in low torque applications, where the joint cannot be exposed to traditional levels of tightenting. In a wheel nut application, the nylon insert will make 3/5ths of fark-all difference.

If a wheel nut is properly torqued, it won't matter if it's a nyloc or not. As such, it's the metal to metal engagement that matters, not the nylon engagement.

[mkpatrol]

No it doesnt but I was using the article to indicate the "in safety" principles. The principle is the same for any nut weather it be castellated, metal/nylock or retained with a good old spring washer.

The first half of almost any thread on most bolts starts with a slight taper so it is really not effective, I see where you are coming from on the full engagement thing but you really dont have that until half way into the first thread.

I guess what I was trying to say to the OP is that if his nylock nuts are sitting flush then that is not really acceptable (for me anyway) & I would be fitting longer bolts/studs or looking at a washer type retention system that will bring the nut back into safety.

Edit: I dont disagree with your original comment other than the fact that I would not be entirely happy with the nut the way it is. As you know, the idea of the locking mechanism is that if the nut does lose its tension, then it does not wind off & cause a catastrophic failure, if the nut comes loose in this case & is only 1-2 threads into the nylock, the nylock may not be able to stop this.

Just my thoughts & has been working for me for 23 years

[80's_delirious]

Having 1.5 threads protruding is a standard on structural engineering too. I was told it is because most bolts have rolled threads which leaves the first thread tapered therefore you don't get silk engagement on the first thread.

If the Nylock nut is flush, the steel threaded part would be fully engaged and if torqued to specs, would expect it to be fine, though maybe not ideal.

[-Scott-]

in this case & is only 1-2 threads into the nylock, the nylock may not be able to stop this.

Just my thoughts & has been working for me for 23 years

I have no issue with using a "rule of thumb", particularly if it's on the conservative (safe) side. And with most styles of nut, it's good to use.

I agree that only 1 -2 turns into the nyloc won't be as effective, but as 80's pointed out, in this application (wheelnuts) it's the metal to metal engagement that is providing the strength, and properly torqued, it should be metal to metal friction that prevents the nut from coming undone.

I would be comfortable with GU's arrangement.

[bru21]

Nylocks are rubbish, they fall off! I have had about 10 fall off over the years - new nuts too, not reused ones.

Cone locks are where its at!

[Ice]

loctite is where its at

and yes in a pinch you can re use nylocs if you use loctite, not reccommended but it will work

[GUtripper]

I' m going with what I've got at the moment, some thread locker compound hasn't hurt either.
In another 3 months the hubs are coming apart again to check bearings etc ( had some issues) so will have a good look at things then.

Note I haven't had to replace all the long studs, so only a few are short as per first post.
Will see.
Thanks for feedback and comments