Slalom4me

Do Distorted Thread locknuts provide greater vibration resistance
to loosening than Nylon Insert locknuts?

The DT nuts in question are conical on one side and this cone shape
is deformed slightly into a triangle, distorting the ID and the threads.
They seem to require noticeably more torque (hand felt) to tighten.

.

WNDOPDLR

The nylon type loose their "lock" if removed and reinstalled too frequently. I have never had that happen with the distorted type. You also need to be careful with the nylon type anywhere they might be subjected to heat.

Carl Johansson

Hey Ken,
I have had the same experience as you - it seems to me distorted threads do give better vibrational loosening resistance - I have to crank on the wrench all the way till the end - while with Nylon - it gets progressively easier. so thats what I base my completely non scientific opinion on!

Carl

jwt1603

OK, so this is all new to me. I've never heard of these DT locknuts (not that I know everything!!!) but sounds like a good idea. Where do you get them? I would guess Home Depot doesn't sell them.

One other question, do they eventually ruin the threads on the stud / bolt you are using them on because of the way it stretched the threads?

67 fastback

Dt nuts do damage the threads of the bolt or stud.

Never use nylocks on anything that deals with temps greater than 200 f. the nylon melts out.

there's a great book by Carol Smith on fasteners.

It hurt my head with the tech.

Safty wire ing is the way that one should lock their fasteners down

Slalom4me

Thank you all!

I was CERTAIN there was something wrong with the situation but I
couldn't put my finger on the root cause of my unease.

I own Mr. Smith's excellent book:
But I didn't have it with me. Obviously, I hadn't read it well enough to
absorb the information. (Nor did I have the clarity of mind at the time
to intuit the problem on my own.)

Although I was asking about vibration resistance in the original post, I
was missing the nature of the real problem. For an engine compartment
application like the one I was questioning here, the KEY shortcoming of
nuts with a nylon insert is their low ceiling for heat tolerance.

As WNDOPDLR and 67 fastback both point out, the nylon becomes soft
and eventually flows or burns - no longer providing any locking function.

Mr. Smith states 250º F is the critical temperature for AN-365 (MS20045)
full height and AN-364 (MS20064) half height rated versions. The
commercial versions from the local hardware store that we mortals are
more likely to use may well only be suitable to 200º.

In contrast, Mr Smith writes that the elliptically offset (Distorted
Thread) lock nut is available in values up to 300,000 psi and 1400ºF.
On the matter of reusability, he writes that:
jwt1603 - one source of information and supply for Distorted Thread nuts
is McMaster. Type 'nuts distorted' into the search field and this will take you
to the general page from where you can drill down further. Pegasus Racing
lists a variety under hardware. There might be some technical
info at SPS Technologies

Again, thanks for directing my attention to the real issue.

.

WNDOPDLR

You might also look for the Fastenal Distributer in your area. Great source for all hardware and usually much cheaper than McMaster Carr.

67 fastback

be leary of where you buy your fasteners from.

there's counterfit bolts out there.

jwt1603

I've tried fastenal before. Great selection but they won't sell just one or two bolts or nuts. The stores here make you buy a full box of 100 if you want something.

leaftye

I have it right here. Here's what Carroll Smith has to say about Nylon collar elastic stop nuts & heat:

And him on elliptically offset elastic stop nuts:

Slalom4me

One possible lock nut candidate for environments where nylon insert
lock nuts are not suitable is the Stover® lock nut.

These are described as being reusable and capable of withstanding
operating temperatures up to 450°F. They are rated as Grade C
and are typically finished with a zinc dichromate coating that gives
them a silver/grey appearance. I also see they are available in black
phosphate.



This is what I've used for my situation.

.

davidfarmer

I prefer nylocks, but maybe it is just because they are easier to use. Even the "crimped" nuts lose their locking capacity after use. For instance, the lower control arm nuts are supposed to be replaced on the C6Z.

I pretty much use nylocks for everything these days, even if vibration isn't a problem. Just eliminates any doubts.

Slalom4me

I wrote above that the Stover nut has a Zinc Dichromate finish - I
checked afterward because I was repeating info from fastener sites
but I was sure that a Zinc Dichromate coating gives parts a
yellow/gold finish.

The fastener sites must be wrong because the nuts have a silver/grey
appearance and this suggests they are finished in Zinc Chromate (as
opposed to Zinc Dichromate)

I'm in complete agreement. It is just that this particular location
gets warm and the Nylock nuts simply didn't feel like they were going
to provide secure locking.

I'm yet to be convinced that the Stover nuts won't wear threads on
the bolts they're on. But these bolts are simple to replace and the
peace of mind is worth while. I'll continue to use Nylocks in more
temperate locations without reservation.

Again - thanks to everyone who commented.

.

UstaB-GS549

There is a lot of confusion even among some platers. Zinc chromate plating can be left clear, dyed yellow, blue (metric), olive etc. There are also trivalent & hexavalent specifications. They are all about the same in my experience and provide minimal protection against corrosion.

Bill Hetzel

I've gotten away from the crimped locknuts on everything except to attach brake discs on some cars. I use standard nylocks on all noncritical assemblies and replace them when they start to feel weak, they're cheap.

I've switched to aircraft AN stuff everywhere else.

The comment about crimped nuts distortion the threads is interesting. I find that even with the aircraft stuff, the nylock nuts start to loose the clamp force after maybe the 4th time they're used. I change them fairly often.

Any idea what the difference is between the crimped nut an the Stover?
And, did you get some Stover's to try out?