Gunsmithing steel "sleeves" in aluminum for steel screws

[longshot2000]

I want to put some steel screws into an aluminum rail for an AR type weapon. I know the big manufacturers put a small sleeve into the hole, to avoid any galvanic response. You can see this in the following photo, looking at the screw threads, and again in the 2nd pic, and the bottom right screw. Typically, what I see is some pink or purple colors, so there must be an epoxy that is also applied.

1) What is this called ?
2) If I wanted to do this, where would I send work for some small screws?

 

[missed]

Maybe a helicoil that is loctited in there with red loctite.

http://www.helicoil.in/helicoil.htm

There easy to install as long as you can drill a hole and tap it.

 

[Anchor Zero Six]

Yes those are helicoils. Also used in steel when threads get stripped out.

 

[softcock]

To stop Galling ? or manufactures possibly doing this primarily to make the Aluminum item that is tapped stronger structurally and also making less stripping to occur .? ,
I been torquing steel screws into tapped hole of aluminum Ring sets and some were together for several years bore taking apart . Never been noticing, 'galvanic response' ? . I do usually put a little anti-seize on all items threaded together .
.

 

[longshot2000]

Maybe a helicoil that is loctited in there with red loctite.

Yes, that is the word I was looking for. I will look into that. If this were beyond my capabilities, where would I turn for some small work ?

 

[missed]

A reputable gunsmith or machinist should be able to tackle it. Helicoils are often used where removal and installation of fasteners is frequent in softer materials, or materials prone to galling. You can also have larger surface area on the softer material in this case.

 

[Gunfighter14e2]

Here is what your looking for, much better than Heli-coils in Alum
http://www.yardleyproducts.com/

 

[GH41]

I like these >> http://www.timesert.com/ but helicoils have been around a long time and are used by the thousands assembling aircraft. I read somewhere that the space shuttles have over 250,000 helicoils in them! I don't know how thick the metal is he needs to thread but the helicoils require a minimum depth to hold. The minimum length varies with thread pitch and diameter of the insert. They aren't hard to install but the cost of the tooling wouldn't be worth it for just a couple of holes. Motorcycle and outboard motor shops would be good places to ask. Their minimum charges are probably less than a real machine shop. It's the kind of thing someone on their lunch break would do in 5 minutes for a twenty dollar bill.

 

[longshot2000]

They aren't hard to install but the cost of the tooling wouldn't be worth it for just a couple of holes.

I think that is true. The holes I need are also small and very short, and I am not smart enough to look at the threads on a bolt and tell the thread pitch.

Thanks for all the help.

 

[Wannashootit]

Without moisture, galvanic corrosion CANNOT occur. IMO, this is overhyped minutiae, unless perhaps it's a hunting rifle that's gonna be subjected to rain/high humidity for extended periods of time.
For rifles that are babied, kept in an environmentally controlled environment (not the least of which is a safe with DampRid or electric rod) it's not an issue.

Steel screws have been used in millions of aluminum mounts without issue, never a bad idea to remove, clean, re-loctite and torque back in occasionally especially if it's kept in a non-conditioned environment.

 

[GH41]

I think that is true. The holes I need are also small and very short, and I am not smart enough to look at the threads on a bolt and tell the thread pitch.

Thanks for all the help.

How small is small and how thick is the metal? What are you trying to mount. If you are trying to put something in/on the main body of the tube it probably ain't thick enough. If that's what you are doing you need to do it the old fashion way. (Pre-Keymod) Use a "T" nut or a steel backing plate. What are you trying to mount?

 

[sirhrmechanic]

You can also get tapered threaded pins from Irontite. You drill the hole and ream with a taper reamer. Then taper tap it. When you put the steel pin in, it will tighten into the taper. Cut off and machine off flush. Then you can drill and tap. Put the plug in with Red Loctite and you won't ever have to worry about electrolytic (which won't matter anyway if your gun/scope/part is not exposed to moisture.

But Helicoils are really reliable and a standard fix.

MSC co. has all kinds of thread inserts and products, too. Probably Grainger, too. But I tend to order from MSC.

Cheers,

Sirhr

 

[sandwarrior]

I would just install your screws with locktite. That will keep any oxygen or moisture out of the hole. If you want strength, a helicoil will work and if you want more strength as in a shallow application an insert will work.

Unless you are putting massive loads on this piece, it's not going to come apart or corrode.

 

[FatBoy]

Have you considered something like this? This is obviously a cheap kit but Fastenel should have something really nice (hardware wise). These won't work on blind holes. The one below is cheap enough to practice on some junk and see how you like it.

https://m.harborfreight.com/45-piece...not%20provided

helicoils and timerserts are easy to use. Pretty common repair when someone strips the spark plug threads in an aluminum head.

 

[mcfred]

Longshot, that is a 'locking' Helicoil. The flat indicated in the below pic is a telltale. The red stuff is their flavor of a dry lubricant for anti-galling. Most Helicoils are stainless so if you use stainless fasteners there might be some issues. There are a dozen types of inserts but unless you're constantly threading/unthreading things then it should not matter enough to use an insert. If you're worried about galvanic corrosion use stainless fasteners in Aluminum. For aluminum it's best to use coarse threads too, not fine.