Loctite is a wide range of adhesives for everything from hobbyist to mechanic to building construction to military industries including epoxies, sealants, super glues and expanding foam. Thankfully, for gunsmiths anyway, there are also thread lockers.
Manufactured by
Henkel Adhesive Technologies, Loctite comes in four basic colors, at least the versions commonly used by gunsmiths:
Red
These are generally considered permanent, high strength thread lockers, designed for screws and locations where the installed item will not be removed in normal use. If you need to remove red Loctite, it will require heating the part to a temperature greater than 550 degrees Fahrenheit. The best way to do this is to heat the screwdriver while it is inserted in the screw head, or you can use a soldering iron held to the screw for 30 seconds or so.
Loctite 263 is a standard red thread locker, while Loctite 272 is a high temperature version.
Dawson Precision uses this grade of Loctite on all their rear gun sights and those with screws.
Blue
These are a medium strength thread locker, able to be removed with standard hand tools. If the screw or other item will be removed or loosened in normal use, such as a sight that might need to be adjusted, the blue group are usually the ones you want.
In general, you will see two versions of blue Loctite available, numbered 242 and 243. 243 is simply an upgraded 242 with better tolerance to oils, and would be recommended for use on firearms.
Purple
This color of Loctite is a low strength thread locker designed for small screws, such as those used on many gun sights, and can easily be removed with the same hand tools used during assembly. Purple Loctite only comes in a single number version, 222, and works perfectly for the small screws in eyeglasses that tend to work themselves loose, as well as small screws in firearms, such as sight screws.
Green
This group is a wicking thread locker and is designed to be used on pre-assembled parts. If you have screws that need to be locked in place but can’t or don’t want to remove them to apply thread locker, the green varieties are for you.
There are basically two green thread lockers useful to gunsmiths, number 290 is a medium to high strength thread locker for smaller screws and 220, which is the high strength version. Both of these will require heat to remove, so do not use them on parts that will normally be disassembled.
Other Products
There are some other Loctite products that gunsmiths may find useful. For example, Loctite Retaining Compound, a green variety, is used to effectively glue metal to metal surfaces. In one of
Larry Potterfield’s Midway gunsmithing videos, he shows how he uses Loctite 680 Retaining Compound to fasten a metal shim on the pivot surface of an old Remington 1900 double barrel shotgun. Loctite 620, another retaining compound variety, is used by Dawson Precision to fasten all front sights that are not intended to be removed and are not held on by screws or posts.
Any gunsmith will want a bottle of Loctite in their shop, likely several different bottles. Numbers 222, 243 and 272, purple, blue and red, provide a good variety for gunsmith use. You might consider having a bottle of 290 for wicking into existing fasteners and possibly a bottle of 680 for permanently fastening shim stock.
Any oil or old Loctite on the threads will make for a weak bond. Cleaning the fastener well, using mineral spirits, will make for a very successful lock. Clean screws might mean you’ll never need a red Loctite.
And yes, each Loctite group is a different color liquid. But they all come in red bottles. Watch the numbers and, if in doubt, check the manufacturer’s web site. Thread lockers are made by several different manufacturers, all of which are similar, but you may want to test a different version to ensure it meets your needs.
Loctite is cheap gunsmith insurance but, fortunately for those who earn their living doing this, can cause problems if used incorrectly or excessively. A little goes a long ways here.
Good information. 90% of the time when I use LocTite, it is 242. However, I have most of the other ones you mentioned for their unique properties. For instance there are times I will use the red (permanent) instead of welding or silver solder. I have used the red to hold in custom screw-in bushings to repair messed up threads in receivers. A little cold blue on the new part and one can hardly tell there has been a repair.
Also, I use a little more aggressive solvent for cleaning the threads–namely acetone on a Q-tip. A quart of acetone used one Q-tip at a time lasts for years.
Jeff, great read. Thanks for all the detail. I’ve used 222, 242, etc for years but being its getting close to Christmas season, I’ve once again run across those porcelain figures that have broken arms, etc and in the past have used various glues to try to mend them. Last month I found LOCTITE brand super glue. WOW …. that stuff puts Gorilla, Super and other brands to shame. I am now my “brides” hero once again. Stuff is awesome.
Great read I will find this information handy both at my gunshop and at my workplace. Thanks again
Very good read, thank you. I am using Loctite for decades in my RC model hobby. Your overview is just perfect, spot on. Perhaps just to add. Use only very little in all applications. A drop, that will be wiped out by cloth from the thread before assembly is just right amount.
Thank you Petr
Great info, I never knew the Green was for pre-assembled parts. All I ever use is the Blue 243.
Thanks for the breakdown and uses of the different thread lockers. First time I’ve ever heard them explained clearly.
Great read and some really good information. I’ve used Loctite for years but this is the first time I’ve ever seen a breakdown on the different types before. Thanks.
Thanks Jeff for the breakdown on the various forms of Loctite. Good information and well written. Thanks again.