What's the best epoxy out there for this?

[amlevin]

I want to install a steel picatinney rail to a steel action and not rely totally on the mounting screws to hold it in place. In fact I would like for the screws to be merely "along for the ride" and if they were under no torque at all that would be great.

In order to bond a rail like this to an action what's the best, strongest, epoxy available without having to have someone smuggle some "secret stuff" from a government research facility 8)

I have both J-B Weld and Devcon steel putty on hand but in my mind they are more "fillers than a bonding adhesive.

Any recommendations out there for something I can either buy at a hardware store or at the most, Grainger? Both surfaces will be close fitting and blasted to a clean but "toothed" surface. Once cured I have no plans for ever removing this rail so I want the toughest, meanest, stuff to hold it there just short of TIG welding.

 

[Ledd Slinger]

Gorilla makes a two part epoxy that is the strongest adhesive I have ever encountered. Doesn't expand or shrink and initial set up time to where you can handle it is fairly fast. Total curing time is pretty quick too. It comes in a double tube syringe type applicator. Just squeeze the two parts out, mix them together and apply. It is clear in color too so it can blend in with what it is going on.

But beware, once set, I don't think you'll ever get it back off. So make sure it's the base you REALLY want to have on there I highly doubt there is anything else out there that is as strong as the Gorilla epoxy

 

[akajun]

Acra glass, it's thin enough to get into a tight fitting joint like that and is clear.

 

[carlsbad]

Bedding a scope base is somewhat common. Your understanding that bedding compounds are not good adhesives is incorrect. We have to use release agents very carefully to keep from creating a permanent bond.

A good scope base such as a nightforce has a recoil lug than hangs over the rear of the ejection port. Other than bumps and transport loads, there isn't much load on the screws. So I'm not sure I would do the permanent thing you talk about. I'll suggest a semipermanent setup below.

To bed a base it is normal to dremel off the bottom finish leaving an uneven bare metal finish that the epoxy sticks to permanently. Do this to the matching rifle surface and your bedding job will be permanent.

A semi permanent option would be to dremel the scope base but don't dremel the action, just clean/degrease it. You would at least stand a fighting chance of getting it to release someday if you need to. But if you really want to make it permanent, rough up the surface of the action under the base. I would start the roughening about 1/16" away from the edge so it doesn't show and you get a good fit and fiinish.

I like the Devcon epoxy. Yield strengths about 1/2 of aluminum.

--Jerry

 

[bheadboy]

I believe that all epoxy's will release with a significant temperature contrast, metals expand at one rate and epoxy at another, thus all will release if subjected to cold, as metal will contract away from the epoxy.

you will be able to separate when wanted.

Bob

 

[jds holler]

I have even used silicone calk in the situation that you describe. Makes for a perfect fit, a good deal of adhesion, and no future headaches. jd

 

[Dusty Stevens]

That thin of a joint under shear stress will still need the screws. Epoxy will only ensure 100% contact. It needs to be pinned like most BR actions if you dont trust the screws. Go to a #10 size and dowel pin it. Glue wont cut it. I dont care what secret adhesive you can steal from the govt developed from alien embryos give me 5mins with an iron or 3seconds after an hour in the sun and ill softly tap it off with a soft face hammer every time. Its just a bad joint.

 

[Keith Glasscock]

We use some pretty neat stuff in the aerospace industry. Most of it isn't easily available.

That said, it depends on what you are trying to accomplish. For example, if you are attempting to stiffen the action through the bonded application of a one-piece scope base, JB weld will do what you want. You will have to torque the screws repeatedly to express the glue from the contact points and leave a small fillet on the outside to get maximum strength.

As pointed out before, screws or pins are still needed to absorb the shear forces.

 

[Rpbump]

JB weld can be machined after it sets and bonds as well as the best epoxys. I have
used it for bedding actions.

Rpbump

 

[amlevin]

We use some pretty neat stuff in the aerospace industry. Most of it isn't easily available.

That said, it depends on what you are trying to accomplish. For example, if you are attempting to stiffen the action through the bonded application of a one-piece scope base, JB weld will do what you want. You will have to torque the screws repeatedly to express the glue from the contact points and leave a small fillet on the outside to get maximum strength.

As pointed out before, screws or pins are still needed to absorb the shear forces.

Stiffening the action is exactly what my goal is. Once installed, I doubt I would ever want the rail to be removed.

As for "expressing the glue" this is why I am looking for an epoxy rather than the typical epoxies with metal fillers. I merely want an adhesive and the "fit" before I glue it down will be about as perfect as one can get, even to the point of being "lapped". I was still planning on using mounting screws as "retainer/locators" but also want the adhesion to be spread across the entire mating surface rather than just focused around the screw holes.

BTW, I'm located near a large Boeing factory. Maybe I need to see who I know that works in an area where they bond steel to steel. What the heck, I only need a tablespoon or so of epoxy and hardner.

 

[Dusty Stevens]

The best stuff the many salesmen ever showed me was a loctite 2 part- one spray can primer and a super glue type tube. Our test was always gluing a penny to our shop floor. It lasted a year with 5 dudes kicking it every time we went by it. Every other glue didnt last a day. Thats how we gauged epoxy/glue ability. I think it was designed for aerospace applications but not sure

 

[amlevin]

The best stuff the many salesmen ever showed me was a loctite 2 part- one spray can primer and a super glue type tube. Our test was always gluing a penny to our shop floor. It lasted a year with 5 dudes kicking it every time we went by it. Every other glue didnt last a day. Thats how we gauged epoxy/glue ability. I think it was designed for aerospace applications but not sure

I remember seeing a lot of coins glued to counter tops in past years and a Loctite display right next to it in past years.

So far in my quest I've found an adhesive that seems promising. Loctite E-120HP Hysol Epoxy Adhesive has a 4,300 PSI shear strength and my rail has approximately 3" of bonding area. That would give me 13,000 psi of "bond" which should be more than enough to keep a NF 12-42X56 NXS and rail in place, leaving an extra 12,998 lbs of bond to stiffent he action a "little". 8) 8)

A little pricey but still under $20 for more than enough to do this job.

 

[Dusty Stevens]

I bet itll do fine. Ruff it up to give it some "tooth" and degrease 3 times more than you think is enough