Need a fastener locking mechanism for #8-32 NC screw.

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Discussion Overview

The discussion revolves around finding a suitable locking mechanism for a #8-32 NC screw used in a .380 auto handgun's trigger guard. Participants explore various methods to prevent the screw from loosening due to mechanical shock during firing, while ensuring the screw remains removable for maintenance. The conversation includes technical suggestions, personal experiences, and alternative approaches.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes the issue of a #8-32 NC screw loosening during firing and seeks alternatives to standard locking mechanisms.
  • Another suggests using a machine screw with a nylon patch on the threads as a potential solution.
  • A participant clarifies terminology, indicating that they meant a socket head screw and emphasize the need for a steel screw due to stress concerns.
  • Some participants recommend Nord-Lock washers and provide links to resources for purchasing them, noting their effectiveness in similar applications.
  • One participant mentions the use of belleville washers for situations involving vibration.
  • Another shares experiences with nylon self-locking nuts and thread locking adhesives, while expressing skepticism about the reliability of locking washers in aerospace applications.
  • Several participants engage in light-hearted banter about firearm preferences and concealed carry, with some sharing personal anecdotes related to shooting experiences.
  • A later reply confirms the successful performance of the Nord-Lock washers after testing them in practice.

Areas of Agreement / Disagreement

Participants express a variety of opinions on effective locking mechanisms, with no consensus on a single best solution. While some suggest specific products and methods, others share differing experiences and preferences, indicating that multiple competing views remain.

Contextual Notes

Some participants express uncertainty about the effectiveness of certain locking mechanisms, particularly in high-stress applications, and highlight the importance of proper torque values and proven techniques in preventing screw loosening.

Who May Find This Useful

This discussion may be useful for firearm enthusiasts, engineers dealing with mechanical fasteners, and individuals interested in thread locking solutions in high-vibration environments.

negitron
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I have a .380 auto handgun which uses a #8-32 NC cap-head screw to retain the trigger guard. During firing, the mechanical shock of the cycling action serves to rapidly loosen this screw regardless of the torque used to tighten it down. I cannot use a standard star washer because they're larger in diameter than the screwhead (there is no clearance between the rear of the screwhead and the trigger guard front) and split-ring lockwashers are useless. This screw must be removable because breaking down the weapon for cleaning requires removal of the trigger guard to disengage the slide, so permanent adhesives like certain types of Loctite are right out. Are there any thread locking devices which might serve the purpose?

Thanks in advance.
 
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Try a machine screw with nylon patch on the threads.
 
Last edited:
Phrak said:
What's a cap head?

Actually, I mean socket head, not cap head. Sorry for the confusion. Also, the screw MUST be steel; anything else will almost certainly shear right off under the stress.
 
Last edited by a moderator:
That's a tough question. I've had a lot of problems with threads loosening in the pumps I design. My favorite method of locking is to use Loctite. I've recently done some testing on various thread locking adhesives and found Locktite #262 works best, at least for my purposes.

Since you specifically mention you don't want to use Locktite however, I'd suggest watching this short movie about Nord-Lock washers.


Their website is here:
http://www.nord-lock.com/default.asp?url=1.16.37

I've seen http://www.google.com/search?hl=en&...&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images"of these washers over at eng-tips.com so if you try them, I'd be interested in how well they work for you.

If you need to purchase them, I believe the McMaster Carr P/N: 91074A115 will work.
http://www.mcmaster.com/#91074a115/=2el6op
 
Last edited by a moderator:
Q_Goest said:
If you need to purchase them, I believe the McMaster Carr P/N: 91074A115 will work.
http://www.mcmaster.com/#91074a115/=2el6op

Now THAT looks promising! I probably have to buy a ton of them just to get one, but c'est la vie. Worth it not to have the damn thing fall apart on the range after 10 rounds.
 
My approach would be to toss that toy and buy a good .45. :-p
 
.45 isn't really good for CC. :wink:
 
A small belleville washer can also do the trick when it comes to vibrating situations.
 
  • #10
I've found nylon self locking nuts, and nylon patch threads are useful without the added bits and pieces. But they do wear-out after several threadings.

In aerospace the various locking washers seem to have a bad reputation. Hmm; I guess I'll have to find out why.
 
  • #11
negitron said:
.45 isn't really good for CC. :wink:

CC? Combat Course? I'm afraid that I don't recognize the initials.

By the bye, I have a lot of respect for the .380, but I hate to admit it.
 
  • #12
CC concealed carry
a quaint thing we have in Ohio were by a citizen can spend $ 100 and a few hours to be trained how to leagally end a home invasion by making the perp room temperature

get some loctite thread locker..or get a .45 ACP
hey, tuff to hide but oh so worth it when you need it
ifin you hit um in the Arm it'll put um down or club um with it
 
  • #13
:smile:
 
  • #14
negitron said:
.45 isn't really good for CC. :wink:

I'm at the age where CC means "closed caption":rolleyes:
 
  • #15
Phrak said:
In aerospace the various locking washers seem to have a bad reputation. Hmm; I guess I'll have to find out why.
Lock washers are one of those things that seem like a good idea but really don't do much for you. The reason being that, for them to do any good, you have to have some way for the lock washer to indent into the joint surfaces which is usually not a good thing and not always possible depending on the materials being used. Plus, when you get the lock washer to actually indent into the material it is in a flat state. There is still debate out there as to whether or not that the locking properties in the flat state are any different than a regular flat washer.

The preferences are to go with proven locking techniques such as thread lockers, safety wire and proper torque values to keep joints from separating.
 
  • #16
Update:

The washers linked to by Q_Goest arrived today from McMaster-Carr. I think we have a winner! I can definitely feel it bite in when I torqued it down. We'll find out for sure when I hit the range this weekend.
 
  • #17
negitron said:
.45 isn't really good for CC. :wink:

Now that Mike has explained the initials, I can say that I'm a very skinny guy (128 lbs.) and carried a Llama Model XV for years. That's pretty much identical to a 1911A1 Colt .45, but with better safeties. Although I had an upside-down shoulder holster, I almost always wore it backwards just behind my right hip in an inside-the-pants holster. It was absolutely unnoticeable, as long as I was careful about my posture. (Remember to bend from the knees.) Don't sacrifice stopping power for concealability. Your life might depend upon it.
 
  • #18
I wanted to update this thread to let everyone know that the Nord-Lock locking washers linked to by Q-Goest performed flawlessly. Problem solved!

Thanks to all, particularly Q-Goest.
 
  • #19
Hi neg'. Thanks for the update. I'll probably consider using them in the future.

On a different note, since you brought up shooting. I had a chance to shoot an M-1 Garand today. First time ever. It belongs to a friend of mine. Lots of fun to shoot, especially considering the history. This one was made in 1945. Although it's an incredably powerful rifle, Loud as hell, and very accurate, it didn't have nearly as much kick as I thought it would.

Some guy walked up to us and told us a story about his grandfather who was in the Normandy invasion, then gave my friend a handful of clips.

There were no Nordlock washers on the rifle...

Interesting day.
 
  • #20
Good on ya, mate. :smile:
 
  • #21
I've just tried 4 times to edit my last post to acknowledge Q's input, and Safari crashed every time. So, I'm just posting this to let you know that I wasn't ignoring Q. He posted while I was composing.
 
  • #22
M1 Garand was one bad weapon..George Patton said it was one of the things that won WW2