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jarhead86
12-01-2015, 07:55 PM
I want to make an aluminum ring box for my wife and have the top laser engraved. Im thinking about 3 1/2 inches OD. I would like the top to thread on. I think UNF or UNC threads would get damaged after awhile. Can anyone suggest a better thread. Pitch isn't the concern style is. Something rugged that wont cross thread easy. Thank you

Toolguy
12-01-2015, 07:58 PM
Acme, Stub Acme, Round Form or Square are all pretty bulletproof.

Bluechips
12-01-2015, 08:27 PM
Be careful with aluminum on aluminum threads. They can gall up and stick. I new a fellow that was building a shooting rest out of aluminum (6061 I think). Both the nut and shaft were aluminum. It was about 2 1/2" OD and had ACME threads. He had finished it and was showing it off to everyone when it just stopped turning. Stuck solid and never moved again as far as I know. His fit was pretty tight for the application. A looser fit might not be so critical.

One of my hobbies is building hot rod cars. A lot of commercially available parts are aluminum or stainless. You are cautioned to use never seize compound on all threaded connections. It's nasty stuff that you definitely do not want on jewelry box, but shows how easily it will gall without precautions.

boslab
12-01-2015, 08:33 PM
Threaded jack leg off Ali scaffolding might work, it's about the diameter, the ones I have is threaded with what looks like square but there is a full rad on the crest if you see what I mean
Mark

Toolguy
12-01-2015, 08:34 PM
Hard anodizing goes a long way toward fixing this problem. It also looks great when laser engraved.

bollie7
12-01-2015, 08:37 PM
What about a brass insert in the lid (nut) to reduce the possibilty of galling? For the thread you could get really tricky and make it a double or triple start
peter

Bluechips
12-01-2015, 08:48 PM
Hard anodizing goes a long way toward fixing this problem. It also looks great when laser engraved.

Sounds like a great idea. You are right about how it looks with engraving. I am beginning to see a lot of aluminum gun parts that get the anodized and engraved treatment. The contrast looks very good.

danlb
12-01-2015, 10:45 PM
The tripple start thread is a great idea. It lets her screw the lid on with only a twist of the wrist instead of having to shift her grip to rotate it several times.

Dan

J Tiers
12-01-2015, 10:53 PM
Acme look nice, and are quite rugged. A multi-start would be pretty slick.

With aluminum, a trace of silicone oil would probably "poison" the surface enough to prevent galling. A loose fit would help too, but once the cover is tight, you are back to the chance of galling in place. You could make the cover locate on an different feature to prevent it seeming sloppy.

The multi start has another good feature: It tends to lift the cover right off, and minimize the amount of rubbing of the two surfaces that close the thing, so they may not gall. And it also is harder to tighten very tight, so galling of the threads might be minimized.

RichR
12-01-2015, 11:29 PM
... but once the cover is tight, you are back to the chance of galling in place.

Add an O ring to bottom out against.

dfw5914
12-02-2015, 01:02 PM
Aluminum on aluminum lathe cut threads will almost certainly eventually gall solid with anything other than a very loose fitting thread.
This is because the quick forming oxide layers shear off in microscopic flakes that slide over each other to stack up and form a wedge that is immediately embedded in the underlying material.
Even a loose fit will gall if tightened to the point of close contact, it's surprising how instantaneous the event can be.

One option would be to thread both halves internally and use a black delrin O.D. threaded insert. Would probably look pretty nice.
Keep in mind, even the flat contact surfaces of the two halves will gall, so the delrin should have a flange to prevent alu/alu contact.

RichR
12-02-2015, 01:23 PM
Take a look at the cap for changing the batteries on one of those aluminum flashlights. They usually have a rubber O ring on them. I
presume it's there to help reduce the force on the threads and prevent the cap from bottoming out.

elf
12-02-2015, 02:24 PM
Aluminum is pretty cheap material. You don't want your wife to get the wrong idea. You should be using titanium or platinum :)

macona
12-02-2015, 02:56 PM
No, its to keep water out.

Frank Ford
12-02-2015, 03:03 PM
Personally, I'd go for something more like a simple "bayonet" mount that would take a quarter turn or less to snug up. It's a box lid, not a pressure fitting, yes?

dfw5914
12-02-2015, 03:19 PM
Aluminum is pretty cheap material. You don't want your wife to get the wrong idea. You should be using titanium or platinum :)

Platinum, definitely make it from platinum.:cool:

RichR
12-02-2015, 03:58 PM
No, its to keep water out.

They even have them on the free ones from Harbor Freight. I doubt they are meant to be water tight. I don't think the lenses are
sealed on them.

Illinoyance
12-02-2015, 05:57 PM
Have you considered a bayonet type closure instead of threads?

Toolguy
12-02-2015, 06:41 PM
He probably has, check post #15.

J Tiers
12-02-2015, 08:47 PM
Multi start thread would be hard to tighten and would tend to pop the cover loose, so it's less likely to gall badly in a way that would seize.

Paul Alciatore
12-02-2015, 10:44 PM
Yes, yes, YES!




Hard anodizing goes a long way toward fixing this problem. It also looks great when laser engraved.