Alternatives for screwing bits of aluminum together

Miroslav · Nov 19, 2017

Hello,

So I'm not really a machinist but I come here for silly questions that I often get really great answers to.

So I'm making a rifle magazine in a hobby project of mine. I want to make it out of two halves (L/R) of high quality aluminum and join them by 2-4 screws. My question is the following: What are my options for threading the aluminum? Are those helicoil things my only option or are there also viable thread standards in larger dimensions that work with aluminum? I'm thinking that a standard thread in aluminum has a very high risk of being stripped.

I don't know if I own a single item that is assembled using helicoil and I don't really know what they feel like. Do you just thread the hole with a special profile, insert the helicoil and then pretend that it's like a piece of threaded steel?

MattiJ · Nov 19, 2017

Properly sized standard metric thread should work well enough in "high quality aluminium" without extra inserts.

Miroslav · Nov 19, 2017

Really? I'm thinking anodized 6061 T6 or similar. M3 or M4 screws.

Limy Sami · Nov 19, 2017

Miroslav said:
Hello,
Do you just thread the hole with a special profile, insert the helicoil and then pretend that it's like a piece of threaded steel?

Nope, .......the helicoil is still in the Alu, and as many have discovered will strip or pull out almost as easily.

I'll venture that if a few M3 / M4 screws in to Alu won't hold a rifle magazine together, it's a bad design, ........BOTOH if they just shake loose, a low strength ''small screw'' Loctite will keep them in place, ........as will several other older school thread lockers.

cranium · Nov 19, 2017

Have you considered riveting the parts together?

DDoug · Nov 19, 2017

"Rivnuts" is another alternative.

Larry Dickman · Nov 19, 2017

Make sure you use Military Grade Aluminum.

Check out PEM nuts.

michiganbuck · Nov 19, 2017

Qt:[I want to make it out of two halves (L/R) of high quality aluminum and join them by 2-4 screws.]
So what is this part like..Their could be design ideas so not needing joining with a thread and screws...???.

lionelt · Nov 19, 2017

Maybe you could use Binding Screws.

Edit add link.

Nickel Binding Screws – Presco

Joe Rogers · Nov 19, 2017

Helicoils advantage is the larger diameter of the insert as opposed to the screw diameter. Further if repeated disassembly is anticipated the insert will resist wear and galling during service.
Joe

SeaMoss · Nov 19, 2017

If there's room, keenserts are way better than helicoils.

Scottl · Nov 19, 2017

It's hard to visualize what your design will look like but unless you are planning to disassemble it stainless screws plus epoxy should be as strong as you will ever need. I routinely use SS screws with aluminum because they are less prone to "galling out" the surface of the thread than black oxide or phosphated ones.

Glug · Nov 19, 2017

Miroslav said:
So I'm making a rifle magazine in a hobby project of mine. I want to make it out of two halves (L/R) of high quality aluminum and join them by 2-4 screws.

How are the halves otherwise located and registered to each other? Is there a machined lip that is captured along the majority of the contact face? If so, the fasteners only need to provide tension and will be much more robust.

If you cannot machine a proper lip, what about dowel pins?

MrWhoopee · Nov 19, 2017

Assuming this is not intended to be disassembled and reassembled repeatedly, there's probably no need for any sort of thread insert. Any of the higher strength aluminum alloys (6061, 2024, 7075) should be more than adequate. Loctite and done.

Tony Quiring · Nov 19, 2017

In a past life Motorola used T10 driver sized metric self tapping (form threading) screws that were amazing and we used them for all sorts of things.

Requires proper drill selection and if no plans for tear down a drop of thread locker works as lubrication then locks in place.

Must be a common off the shelf screw.

Makes for better outcome as no worry about breaking taps.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

Conrad Hoffman · Nov 19, 2017

Or, take it to somebody that does good TIG work on aluminum.

Larry Dickman · Nov 19, 2017

or spot weld it.

Or, maybe post a god damn picture so we know what you're trying to do.

bridgedog · Nov 19, 2017

Just make sure you use billet aluminum. :popcorn:

michiganbuck · Nov 19, 2017

bridgedog said:
Just make sure you use billet aluminum.

Yes, don't bill it SS if you make it of aluminum.:popcorn. :stirthepot:

72bwhite · Nov 19, 2017

or just use the right glue,
quite a few modern car body panels are glued on these days

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