Rich;
There are all sorts of cheap hardware out there that look like aircraft
hardware but aren't.
"Nyloc" is a trade name for one vendor's "prevailing torque locknut" but
there are others. Esna is one manufacturer that makes them. When those
locknuts first came out around WW II, the insert was made of a tough fiber.
Later, the material was switched to nylon. The idea behind the nylon insert
is to assist in keeping the nut from spinning off the bolt under vibration.
The primary locking mechanism was tightening the nut on a bolt to its
specified torque; the "prevailing torque locknut" simply added a measure of
additional safety. The nut's locking mechanism was NOT intended to provide
adequate safety by itself!
For locknuts to be effective, the nylon insert needs to be accurately sized
and of the proper grade of nylon. In addition, the bolt pitch diameter must
be correct and the thread profile needs to be in spec. Commercial hardware
doesn't have the standards that aerospace and MIL-spec hardware does. The
quality control of some commercial hardware is so pitiful that I've seen
nuts and even bolt without any threads.
There are all-metal "prevailing torque locknuts" that are used in areas
where the temperature is too high for nylon types. Generally, they have
higher torque but I wouldn't rely on this type of nut alone, either. Loctite
helps but you can't beat a cotter pin or safety wire.
Carol Smith's books address this question very well.
Regards, Neil Tucson, AZ
-----Original Message-----
From: Richard Kensicki [mailto:richk@spartajunction.com]
Sent: Thursday, February 20, 2003 6:49 AM
To: Land-speed@autox.team.net
Subject: Nyloc nuts, safety wire and cotter pins
On another forum I'm on a member warned of finding his suspension
lowering kit loose. The nyloc nuts were no longer tight on the
adjustment bolt where they should be. Fortunately he drilled for cotter
pins on the bolts. Now I remember from my days as a mechanical tech.
that the rule of thumb was that nyloc nuts were considered a one time
use. But we was always using them in under tension, that is they were
torqued down causing the material to deform. I think this kit maker was
miss using them.
There should be at least one knowledgeable member here that can comment
on their proper use? I think what the lower kit really needs is a
deforming nut (castleated?) and copper pins for safety.
RichK
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