Gunsmithing Aluminum to steel bonding?

HSNARC · Feb 9, 2024

I know the traditional method for attaching a sight base to a receiver or barrel would be drilling/tapping +/or silver solder.

What if the piece to be attached is aluminum and the barrel is chromoly? I know some wizard like C.Dixon could tig or solder it just right, but I tig like a toddler fingerpaints.

Is there an effective high strength epoxy solution? Mix it up, gloop it on and go? Maybe something a little more application specific than JB Weld? I don’t think JB weld would hold up to heat+recoil super well.

Trigger Monkey · Feb 9, 2024

Specifically what are you trying to do? What's the aluminum piece? What type of firearm? What caliber? Where are you trying to attach it?

We're going to need details to give any kind of competent answer.

HSNARC · Feb 9, 2024

Trigger Monkey said:
Specifically what are you trying to do? What's the aluminum piece? What type of firearm? What caliber? Where are you trying to attach it?

We're going to need details to give any kind of competent answer.

Generic aluminum sight base https://www.midwayusa.com/product/1005994416?pid=453735

Stuck onto the oem barrel of a yugo 48 (already bubba’d) Mauser in 8mm where the factory rear sight was soldered on.

Bantam1 · Feb 9, 2024

As far as I know you cannot tig weld aluminum to steel, or weld any ferrous to non ferrous metals. I could be wrong but I have never seen it done or heard about it before. I know there are some different solders out there that may allow you to solder different materials to each other. The bond will just be the solder.

Taylorbok · Feb 9, 2024

Why not solder?
I also wouldn't doubt if JB weld held it on just fine

MAHLMAN · Apr 19, 2024

https://esab.com/us/nam_en/esab-university/blogs/is-it-possible-to-weld-aluminum-to-steel/ will take you to some good information. This is not novice welder work from what I read. Way to complicated and if you can't mechanically put them together perhaps some bonding agent + screws would work. I have been tig welding since 1981 and I would not attempt any of the possible methods offered in this article on a firearm with heat treated steel and anodized aluminum and the additional coating on your barrel/receiver.

My advice would be to forget anything that requires heat.

Yondering · Apr 22, 2024

Obviously this depends how much of a ghetto bubba job the OP is trying to do. JB weld is pretty hard towards the ghetto end of the spectrum, not something I'd be willing to have or depend on for my rifles. Solder can work, but requires some practice to do a good job of it; if someone's wanting to go with JB weld or other epoxy solutions they may likely not have the skill or background to do a good solder job.

Of course the right way to install a sight base like that is to drill & tap the base material and screw it down. Should be two screw holes in that sight base. Fairly easy job for a competent gunsmith. Personally I'd suggest for OP to take it to someone who can do this; it shouldn't be all that expensive and will give the best end result. Even on a cheap project rifle it's worth learning to do things right rather than do bubba work with epoxy and bailing wire, IMO.

Threadcutter308 · Apr 22, 2024

I hope the OP isn't going to put an expensive scope on this rig.........

sirhrmechanic · Apr 22, 2024

You won’t solder aluminum to steel either.

Best bet would be old-fashioned screws and bed in an industrial epoxy like 3m Scotchweld (scotch bond?). It’s basically the stuff they use to glue airplane wings together these days.

As said above… if you are even asking the question about tigging… take it to a ‘smith.

Drill and tap blind holes. Fit base with screws. Bed base and screws in quality epoxy. Should work. Make sure you take into account things like how massive is rifle… weight of scope and how hard does rifle kick when figuring out base screw needs. Heavy scope on light rifle with a hard recoil impulse won’t last u less very firmly attached.

Sirhr

Mike Casselton · Apr 22, 2024

Maybe try B-Square.

HSNARC · Apr 22, 2024

No scope, just a sight base for irons. I think I’ll just drill and tap with epoxy. It’s just a fun project, nothing serious.

Also there is no such thing as a “competent local gunsmith” kinda why I’m learning to bubba my own stuff. I’ve thought about it a lot and have sorta developed a theory. Central il is probably the blackest richest dirt in the world. Can’t build a range to shoot, that would cut down on valuable corn production. Nowhere to shoot guns don’t get shot. Nowhere to shoot no one cares about custom work. Everyone supports agriculture, not much work for manual machinists and gunsmiths. Plenty of big deer (see corn production above)but the state won’t let you shoot them with anything resembling a fine firearm (straight wall now but just this year). I live in a town with 150k people and not a single actual “gunsmith” maybe a few ar builders and Uber serious trap shooters but that’s it.

Mike Casselton · Apr 22, 2024

@Rthur

hero's machine · Apr 22, 2024

You could run a steel sight and solder it. You can drill and tap. Anything else is going to be less than reliable.

Yondering · Apr 23, 2024

HSNARC said:
No scope, just a sight base for irons. I think I’ll just drill and tap with epoxy. It’s just a fun project, nothing serious.

Also there is no such thing as a “competent local gunsmith” kinda why I’m learning to bubba my own stuff. I’ve thought about it a lot and have sorta developed a theory. Central il is probably the blackest richest dirt in the world. Can’t build a range to shoot, that would cut down on valuable corn production. Nowhere to shoot guns don’t get shot. Nowhere to shoot no one cares about custom work. Everyone supports agriculture, not much work for manual machinists and gunsmiths. Plenty of big deer (see corn production above)but the state won’t let you shoot them with anything resembling a fine firearm (straight wall now but just this year). I live in a town with 150k people and not a single actual “gunsmith” maybe a few ar builders and Uber serious trap shooters but that’s it.

Drill and tap would be the right way to do it. You could bed it with epoxy as well, but really not necessary for an iron sight base. That's a very similar style rear sight base as production Remington 700 rifles have used for many years, with just two screws holding it in place; no epoxy to be found.

I don't recommend trying to drill and tap a barrel yourself though unless you really know what you're doing. Super easy to end up with screw holes off center if you're not using a mill and very careful alignment; some sort of jig could work though if you found one or had the skills to make one. This is the kind of job where typical carpentry skills and tooling are not good enough; you'll need to be more precise and exact in the hole placement, starting, and depth.

If you have the ability to find and mark the exact top centerline of the barrel, start with a good heavy centerpunch mark at each screw hole; do not skip that part. (unless you have a mill and can mill flats for each hole location) You'll need to control drill depth carefully, and have plug and bottoming taps at minimum. Best of luck if you try it; it's a skill worth learning but I do recommend trying it on a piece of scrap round bar first.

If you need help selecting screw sizes and tap & drill sizes, let us know, several of us here can help.

308pirate · Apr 23, 2024

hero's machine said:
You could run a steel sight and solder it. You can drill and tap. Anything else is going to be less than reliable.

I slightly disagree. Henkel makes several aerospace and industrial adhesives under the Henkel and Loctite brands that will guarantee that sight won't ever come off the rifle if you apply and cure them correctly.

Aviation supply websites like skygeek and industrial supply places like MSC and McMaster Carr sell them.

hero's machine · Apr 23, 2024

My experience with epoxies and materials with different coefficient of thermal expansions are not what I would recommend. If I were to suggest epoxies I would grit blast the surfaces for adhesion.

Not arguing that I couldn't be serviceable.

308pirate · Apr 23, 2024

hero's machine said:
My experience with epoxies and materials with different coefficient of thermal expansions are not what I would recommend.

I'm talking about adhesives that hold structural portions of aircraft together, including CF to aluminum bonds.

They'll work fine in a rifle.

hero's machine · Apr 23, 2024

As long as your adhesive can have a 2x delta in your CTE....rock on.

It has to work. That's why wrapped barrels outshoot full steel barrels.

Darryle · Apr 23, 2024

Clean, blast aluminum, clean again, alodine, dry, adhesive prime, prep steel and adhesive prime, bond them together with any metal infused epoxy, A4 metal set, JB Weld and others

If done correctly, short of using a chisel and hammer, it will not come apart cold, heat being the best option.

SLinKK · Apr 23, 2024

MAHLMAN said:
https://esab.com/us/nam_en/esab-university/blogs/is-it-possible-to-weld-aluminum-to-steel/ will take you to some good information. This is not novice welder work from what I read. Way to complicated and if you can't mechanically put them together perhaps some bonding agent + screws would work. I have been tig welding since 1981 and I would not attempt any of the possible methods offered in this article on a firearm with heat treated steel and anodized aluminum and the additional coating on your barrel/receiver.

My advice would be to forget anything that requires heat.

Mettalurgist here...you would not ever weld those 2 materials...a tac weld is still a weld. If you needed to make the 2 materials bond like a weld then you would either you friction welding or explosion welding to create a bond between the two materials and then fab a part from the multiple materials. Any polymer based solution will use mechanical adhesion only and would always fail at some point.

MAHLMAN · Apr 27, 2024

SLinKK said:
Mettalurgist here...you would not ever weld those 2 materials...a tac weld is still a weld. If you needed to make the 2 materials bond like a weld then you would either you friction welding or explosion welding to create a bond between the two materials and then fab a part from the multiple materials. Any polymer based solution will use mechanical adhesion only and would always fail at some point.

Friction welding was the only process the to join aluminum to steel or stainless steel that I knew of. But there was the info on the ESAB site and I would hope they know what they are talking about. They certainly did not sound ambivalent about would it work or not.

hero's machine · Apr 27, 2024

This is a company local to me that specializes in dissimilar metal bonding.

https://spurind.com/#top

SLinKK · Apr 27, 2024

hero's machine said:
This is a company local to me that specializes in dissimilar metal bonding.

https://spurind.com/#top

Same concept as explosion welding, using high pressure to create a mixed microstructure interface.

918v · Apr 27, 2024

Why not just fix it with original parts?

918v · Apr 27, 2024

Yugo M48 Rear Sight Base with Spring

Same as FN 98 except for markings. The rear sight spring is included. These are original used parts in Very Good condition. Expect minor finish wear and light scratches, etc.

store.centuryarms.com

Yugo M48 Rear Sight

Same as FN 98 except for markings. See photo two for variations of markings. These are original used parts in Very Good condition. Expect minor finish wear and light scratches, etc.

store.centuryarms.com

SporterII · Apr 27, 2024

Panel bond.

lariat · Apr 28, 2024

308pirate said:
I'm talking about adhesives that hold structural portions of aircraft together, including CF to aluminum bonds.

They'll work fine in a rifle.

This is correct. I use this stuff as 308 described on my bases and they do NOT come off. I also use these adhesives at work for those very flight applications. We have tested them for shock, lack of adhesion, etc.; they flat out work. One thing to be aware of when purchasing them: some will set much faster if you apply heat after getting everything assembled, but will adhere in time without the heat. If you are wise and use screws then this longer set time will not be an issue. If you do want to heat it, the temp is low usually, like 120 degrees for a couple hours. If you catch the right day you can simply throw it on your dashboard for the day. Keep the windows rolled up and point the car to the sun. We actually did testing on this for field expedient repairs on some kit we were developing and it worked exceedingly well.

OP, Word to the wise: if you are going to use any kind of epoxy under the attachments and use screws you need to initially put release agent on the screws so you don’t weld them in. Once everything it set, pull the screws out, clean and put whatever version of loctite you want and toque them down. You really won’t need as much epoxy as you think to do this. Have plenty of qtips and paper towels to clean up what squishes out.

And be damned sure to mock up everything before you do anything permanent. The advice given to test the process on other material before starting on the real deal is very good advice. Your choice of drills and taps are going to be critical - no hardware store BS. If you are planning on drilling and tapping holes by hand I would suggest that you send it out to be done properly as those threads are super fine, the holes small and the chance of breaking a tap are very high.

Edds · May 3, 2024

308pirate said:
I'm talking about adhesives that hold structural portions of aircraft together, including CF to aluminum bonds.

They'll work fine in a rifle.

Can you name a specific product? I would like to try some.

308pirate · May 4, 2024

Edds said:
Can you name a specific product? I would like to try some.

Pick one out of here: https://next.henkel-adhesives.com/us/en/applications/structural-bonding-solutions.html

lariat · May 4, 2024

Edds said:
Can you name a specific product? I would like to try some.

You can also go with the 3M or Loctite structural 2 part epoxies. None of them are cheap.

Here’s a link to Grainger just as an example so you have a list of what’s available. Henkel is very good. The shear strength on some of these is off the charts - not sure you want to put a rail on with something that is rated to 4500 lbs, but they have lower ratings. You can get it cheaper than what grainger is selling it at. I just searched for small containers as you probably don’t want a huge amount.

https://www.grainger.com/category/adhesives-sealants-and-tape/adhesives-glues/load-bearing-structural-adhesives/epoxy-structural-adhesives?attrs=Container+Type%7CDual-Cartridge&filters=attrs%2Cprice&price=0%7C400

Kickin45 · May 4, 2024

As I’m sure someone has already mentioned, JB Weld. Scuff both contact areas with 220 paper, apply JB, wipe excess, tape down, wipe bleed over, wait 24hrs.

308pirate · May 4, 2024

lariat said:
You can also go with the 3M or Loctite structural 2 part epoxies. None of them are cheap.

Here’s a link to Grainger just as an example so you have a list of what’s available. Henkel is very good. The shear strength on some of these is off the charts - not sure you want to put a rail on with something that is rated to 4500 lbs, but they have lower ratings. You can get it cheaper than what grainger is selling it at. I just searched for small containers as you probably don’t want a huge amount.

https://www.grainger.com/category/adhesives-sealants-and-tape/adhesives-glues/load-bearing-structural-adhesives/epoxy-structural-adhesives?attrs=Container+Type%7CDual-Cartridge&filters=attrs%2Cprice&price=0%7C400

3M 08115 is one I've seen around

Loctite is part of Henkel for some time now.

Ziloooo · May 22, 2024

Edds said:
Can you name a specific product? I would like to try some.

In addition to 308's link, you can also reference the Maintenance & Repair Epoxies section on Loctite Sourcebook (a bit easier to navigate). Once they cured, it's solid as metal https://www.ellsworth.com/globalass...e/henkel-loctite-adhesive-sourcebook-2015.pdf

btw will there be gap btw your parts? this will impact your selection. Adhesive in many cases is not supposed to fill gap.

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