Proper use of Loctite & general fastener information

[EVP]

TC on other another great informative post.


It totally makes sense. Some auto manufactures torque critical fasteners in engines by bolt stretch.. They also recommend that these fasteners should not be reused and a new fastener should be installed.

I would imagine that any time the optic and fasteners are removed that a good policy would be be to replace with new quality fasteners. Overkill most likely but gives you the best chance of success.

[Nephrology]

I'm gonna say this should be stickied somewhere.

Agreed

[Controlledpairs2]

Is it possible to excessively wear the blind hole or female end if using fresh fasteners every time to mount and remount the plates and optics? I can't imagine the alloy steel screws from McMaster Carr would be strong enough to wear a slide, but perhaps plates? I have no frame of reference in those tensile strength numbers or personal experience. Thanks.

[OlongJohnson]

Is it possible to excessively wear the blind hole or female end if using fresh fasteners every time to mount and remount the plates and optics? I can't imagine the alloy steel screws from McMaster Carr would be strong enough to wear a slide, but perhaps plates? I have no frame of reference in those tensile strength numbers or personal experience. Thanks.

The steel screws are likely rated at 190ksi (that's typical for socket-head fasteners in smaller sizes) and considerably harder than the slide, once you're through any FNC ("Meloniting").

There's probably a tradeoff, where reusing screws a bunch of times wears the threads and causes them to be deformed and wear the female threads more. But when a new screw is initially used, there is some burnishing that occurs as the male and female threads get better acquainted. I don't know whether using a new screw every time would wear the female threads more or less than reusing it a few times.

One thing I have noticed is that higher quality fasteners tend to have fuller thread forms, leading to a closer fit between male and female threads and reduced wear of both male and female threads.

Using a slightly smaller than typical drill size and a tap designed to create a closer class of fit will improve thread engagement and reduce wear because the forces are distributed on more thread surface area. Most inexpensive, generic taps are designed to give a very loose thread, in order to prevent problems when they are used poorly or with poor fasteners. Taps that cut smaller threads usually have to be special ordered.

[Clusterfrack]

See below for how to use VibraTite:

Adam includes VibraTite VC3 in the package with the CROM.

Expect that anything you fasten to a 12 gauge will work loose as you shoot it if you are not using some form of thread locker. Same goes for slide-mounted optics. It's not a "nice to have", it's a requirement or shit will shoot loose in short order.

Thread locker needs to be applied carefully, including proper degreasing and cleaning of the fastener and the work piece (receiver in this case) to achieve a lasting mount.

I did a little writeup on how LocTite works here:

https://pistol-forum.com/showthread....er-information

That was mainly done to give what the actual manufacturer of the product says about proper use of the product in their own training. I just got sick of reading nonsense about LocTite on the web from people who clearly had no idea how it works.

But I typically use Vibra-Tite VC3 on my optics mounts. (Including handguns, rifles, and shotguns) VC3 sets up more like pine tree sap instead of essentially a more crystal-like solid structure of the LocTite. This seems to make it more forgiving of errors in application, at least in my observation. With LocTite if you don't get it completely clean or you interfere with the curing process with vibration the solid structure you're relying on doesn't set up and so the fastener moves. VC3 tends to do a better job if application is imperfect, and it holds up under the shock and vibration of the 12 gauge very well.

My process for application is simple:

- Use a minimum of 90% isopropyl alcohol (99 is best if you can get it) to pour into a shallow tray. Put on some nitrile or rubber gloves.
- Submerge all the fasteners you will use in the alcohol while you set everything else up
- Pull the fasteners out with tweezers or tongs and set it on a blue shop towel to dry in the open air
- Apply VC3 to the first 1/4 or 1/3 of the threads on the fastener. Note that the "first" threads are those that will be going into the work piece, not the threads closest to the head. I will use a small paint brush (that has also been cleaned in the alcohol) to spread the VC3 around the threads, including pushing it into the recesses of the thread.
- Let the VC3 set up for 5-10 minutes. It should be pretty tacky by that point.
- Tighten the fastener to desired torque. If you've used enough, you'll see just a little bit of the VC3 come oozing out around the head of the fastener.

If you do that and let the gun sit for a couple of hours, things should be fine. I've let it sit for as little as an hour and shot the gun with no problems afterwards. But longer time left alone is better. It doesn't need the same cure time as loctite, but it does need some to set up.

[TCinVA]

One of the things I do to try and get any sort of thread locker to work properly is taking the time and effort to clean out the hole the fastener is going to be going into thoroughly. Some sort of brush is helpful.

Luckily, the typical threaded holes in the receivers of shotguns will allow use of a .17 caliber brass brush. When scrubbed down good with some high concentration isopropyl alcohol and allowed to dry, that procedure seems to do a good job of removing any contaminants that get in the way of Loctite or VC3 setting up as they need to.

For the threaded holes on pistol slides I usually resort to some precision brushes available from McMaster-Carr:

https://www.mcmaster.com/4754A782/
https://www.mcmaster.com/4905A12/

They are especially useful if you need to clear out a prior application of thread locker.