Nylon-Insert Hex Nuts
By Gordon DeWitte
Lex’s recent post on captive nuts reminded me of some other nuts I’ve been using a lot lately while doing some volunteer work on a search-and-rescue van: nylon-insert hex nuts. Depending on which big box you shop at, and whom you ask when there, they’re also called stop nuts, locknuts, or nyloks (although NYLOK® is a nylon material typically applied to bolts and screws), or nylocks. I like them because they resist vibration and loosening, they’re reusable, they don’t damage threads, and they’re readily available. McMaster-Carr has a large variety in their catalog, and many of the big boxes carry Hillman versions.
For higher vibration, temperature, or safety applications (like motorcycle and automobile racing or aviation), safety-wired nuts, or nuts with cotter pins are the preferred — if not required — choice. Other alternatives include two-piece thread-clamping locknuts and distorted-thread locknuts.
A 100-piece package of 1/4″-20 nylon-insert nuts will cost you around $5.
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September 14th, 2009 at 11:33 am
Harbor Fright has box assortments of these. They are quite cheap when they are on sale.
September 14th, 2009 at 12:12 pm
I absolutely hate nylon locknuts. I don’t quite remember why, but I try to use suitable alternatives whenever I can.
September 14th, 2009 at 12:30 pm
For vibration dampening along the axis of a bolted connection - you might try a Belleville washer approach:
http://www.bellevillesprings.com/belleville-washers.html
September 14th, 2009 at 12:37 pm
i personally like the spring type washers when i have a choice it’s seems like starting the nylon ones can be difficult if you are hand starting
September 14th, 2009 at 12:42 pm
Gordon, love ‘em. Though they shouldn’t really be reused in applications where things falling off would be Bad™.
Hey Paul, nice to see my “Harbor Fright” love/hate name is catching on.
ToolGuyd, I’d like to know why you hate them. Haven’t had any pique my hate. Is it because they aren’t pretty and “nylon” ain’t manly?
Fred, I learned something today thanks to you! Knew they existed, didn’t know what they were called.
September 14th, 2009 at 12:53 pm
they are ok. but they and heat don’t get along. most times i just prefer using loctite.
September 14th, 2009 at 1:21 pm
i hate them in aplicatins where they have to be screwed on to a threaded rod because it is a pain to use a wrench to tighten it dwn for 12 inchs
September 14th, 2009 at 2:52 pm
Careful using power tools to install them, ie: drill driver, impact driver, etc. The speed can melt the plastic causing the nut to seize on the bolt making it pretty hard to get off.
September 14th, 2009 at 5:31 pm
What George said. Got these with the locking collars on my motorcycle exhaust. After the 1st ride, guess what.
September 14th, 2009 at 6:24 pm
I thought that these nuts were not reusable so I googled it and found some FAA information on them:
Recommendations for use per FAA AC43.13-1B Acceptable Methods and Practices:
* Elastic lock nuts are not to be installed in areas exceeding 250 degrees F.
* Do not reuse elastic lock nuts if the nut cannot meet the minimum prevailing torque values shown in the chart
* Do not use self-locking nuts on parts subject to rotation
* Do not use self-locking nuts where the loose nut, bolt, or washer may fall or be drawn into the engine air intake scoop.
* Do not use self-locking nuts to attach access panels, doors, or any parts that are routinely disassembled before or after each flight.
September 14th, 2009 at 7:14 pm
I thought the name of that fine establishment was “Horror Fright”?
September 14th, 2009 at 9:57 pm
well they are also only a grade 5 at best
so if your using them any where that has a pretty
heavy load or anything that needs grade 8 your not going to be able to
get away with it
September 14th, 2009 at 11:40 pm
Loctite doesn’t work when it gets hot.
September 15th, 2009 at 5:54 am
Two nuts, torque them together, locked for life! Nuff said.
September 15th, 2009 at 6:35 am
Double-nutting isn’t all it seems to be. The outer nut is susceptible to vibration just like a single nut torqued against whatever you’re securing. The only “locked for life” options are properly used safety wire, or welding.
September 15th, 2009 at 11:15 am
@Joe
How about a castleated nut and a cotter pin?
September 15th, 2009 at 3:49 pm
for heat i use copper metal lock nuts. each situation has its prefered way to secure bolts/nuts.
September 16th, 2009 at 2:08 am
I used to buy these until I discovered medium bond Loctite. The nylok’s often become oily or worn and don’t lock, but the locktite always works with a bit of cleaning and can be used on any size nut.
September 16th, 2009 at 5:50 am
Yeah, fred, I missed that one.
September 16th, 2009 at 10:27 am
Typically in aerospace uses, all metal locknuts (usually called self-locking in the biz) are used. The locking feature is that the thread is deformed into an oval shape, uses the spring properties of the metal squeezing the bolt’s threads to lock. In many cases, we still put a locking device in addition to the self-locking fastener, lockwire, locktabs, cotter pins, etc (called positive locking).
September 16th, 2009 at 7:04 pm
Anti vibe nuts - I like them. No, they’re not good for heat, but for
other applications (such as applications with a lot of vibration),
they’re perfect.
I use them to replace the factory fasteners that vibrate loose off of my
lawnmower.
Especially those oversize ‘wing’ nuts on the push handle that are
supposed to allow the handle to fold; mine just vibrate off and get lost
in the lawn somewhere.
I found these nuts with the nylon inserts to be just the ticket, since I
don’t need to fold the handle.
I give them two thumbs up.
September 25th, 2009 at 12:54 am
You can buy grade 8 nylocks. I’ve got a bag full of 5/8ths grade 8 nylocks along with matching grade 8 carriage bolts for a special application.