Purple, Blue or Red Loctite

U

UncleGrumpy

New member
Hi,

When installing new scope mounts Which grade of loctite should I use. I am thinking of the screw locker ie purple. I use blue all the time an a car though.

Cheers
 
If the screws are ever to be replaced or loosened, then use blue.
It's the one designed for threads and such.
Red is for bearings, especially shell bearings that are meant to stay in place and not spin.
It requires heat or solvents to loosen.
Any other versions are ever harder to deal with.
So, blue it is.
If that doesn't hold things, then more than likely the threads have been drilled and tapped incorrectly.
 
Blue.

Red is for semi permanent installs and Purple is for really small, fine screws.

Besides, you already own blue loctite.
 
Thank you !!!

Purple is for really small, fine screws.
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Who says an old-dog can't learn new tricks. I have been using blue, for years. ...... ;)

Thank you; natman and g.willikers. ... !!! :)

Be Safe !!!
 
Purple (222) works very well for scope base and ring screws.

In my opinion.... If purple Loctite isn't enough to hold, then there's some other issue that needs to be addressed. (The screws shouldn't be backing out, even without Loctite, but that's another subject...)
 
I mounted my first scope on a 22 rimfire back in 1960. Since then I have mounted well over 100 scopes on rifles and handguns and have never used loctite.
 
Seldom used on scopes

Since then I have mounted well over 100 scopes on rifles and handguns and have never used loctite.
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Same here as most of the time, it's really not needed. In fact, only when I run into a problem, do I use Loctite on scope work. Most of the problems have been on high power rifles. I have "never" used it on rimfires. ... ;)

Be Safe !!!
 
I use the green 290 for a lot of stuff. It's a medium grade post-assembly thread locker. Put the stuff together, and let a drop hit the threads and you're done.
 
^^
It is- but from what I'm reading should never be used on scope mounting screws as it's not a "removable" threadlocker. Break loose torque is in the hundreds of in. lbs. You'd likely destroy the screw(s) trying to get them out.

I don't see much difference in break loose torque values between the blue and purple (I've always used blue) and don't understand where the distinction in applications would lie.
 
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Blue is better for 5/16" fasteners and up, purple is better for 1/4" diameters and down, like scope mount screws.

Green in most applications needs a primer as it has a lower threshold to overcome the passivated surfaces which anodized aluminum and black oxide create.
 
The permanent red Loctite, requires heating with a torch to soften enough to remove. That's Loctite's recommendation, anyway. There are both blue and green wicking Loctite's, numbers 220 and 290. The green is rated about 4½ times stronger than the blue version.
 
Heat will weaken red loctite, but strong solvents will also dissolve it.
Things like Acetone and barrel cleaners with ammonia.
But you have to work fast or the red will go right back to doing what it does, and re-stick everything again.
 
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