Material choice for 1.25" threaded fastening
Material choice for 1.25" threaded fastening
(OP)
Hiya,
I'm designing a fitting which will have the male half of a 1.25" screw thread fastening on one end. The female half is being made by another company, and is anodised aluminium. The whole fastening is going to be regularly done and undone by hand - the part I'm designing is kind of an optional add-on.
I know aluminium-aluminium threads have a serious problem with seizing. It's my understanding that anodized aluminium threads also tend to seize, although I'm assuming this is for different reasons.
My material choices are:
Stainless steel (303, probably)
Brass
Anodized aluminium.
Does anyone have any experience of this sort of situation? Anyone recommemnd any particular material? Weight is also a consideration, so the lighter the better.
Ta
I'm designing a fitting which will have the male half of a 1.25" screw thread fastening on one end. The female half is being made by another company, and is anodised aluminium. The whole fastening is going to be regularly done and undone by hand - the part I'm designing is kind of an optional add-on.
I know aluminium-aluminium threads have a serious problem with seizing. It's my understanding that anodized aluminium threads also tend to seize, although I'm assuming this is for different reasons.
My material choices are:
Stainless steel (303, probably)
Brass
Anodized aluminium.
Does anyone have any experience of this sort of situation? Anyone recommemnd any particular material? Weight is also a consideration, so the lighter the better.
Ta
Matt Freeman,
Design Engineer,
UK





RE: Material choice for 1.25" threaded fastening
I've had good luck with using a hard anodize per MIL-A-8625 Type III. Might want to give that a look.
RE: Material choice for 1.25" threaded fastening
RE: Material choice for 1.25" threaded fastening
If it does, could it have a threaded non-metal liner?
RE: Material choice for 1.25" threaded fastening
Matt Freeman,
Design Engineer,
UK
RE: Material choice for 1.25" threaded fastening
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Material choice for 1.25" threaded fastening
Is the part being used to lock/clamp something in place or for positioning?
Is the thread fine or coarse?
Can a lubricant be used?
RE: Material choice for 1.25" threaded fastening
I don't think lubricant can really be used - it's an often handled part, so we can't guarantee the state the customers will keep it in, so it's best to assume it's unlubricated. Sure, you could use something pre-impregnated, but I think that's overkill.
The drawing specifies a 1.25" -20 UN thread. I'm a metric boy myself, but I think that's a coarse thread.
As to the loads - to be honest, I don't have any figures I can give you right now, it's all a bit back-of-fag-packet. I'll try and post some figures before the end of the day.
Matt Freeman,
Design Engineer,
UK
RE: Material choice for 1.25" threaded fastening
As suggested above hard annodized will probably be better than standard for this application.
KENAT, probably the least qualified checker you'll ever meet...
RE: Material choice for 1.25" threaded fastening
Also the brass is going to be easy to produce, will thread easy, and be a completely different color, that way when the guy in the field drops it he can find it again.
Nick
I love materials science!
RE: Material choice for 1.25" threaded fastening
RE: Material choice for 1.25" threaded fastening
Sample callout:
APPLY EVERLUBE 9002 IAW MIL-PRF-46010 TO THE THREADS, .0003 TO .0005 THICK. CURE AT 400 DEG F +/- 15 DEG F FOR 120-140 MINUTES.
RE: Material choice for 1.25" threaded fastening
Matt Freeman,
Design Engineer,
UK
RE: Material choice for 1.25" threaded fastening
Combine PTFE or similar dry film lubricant with anodize to get wear resistance + lubricity. Have professionals do it for you:
Some suppliers:
In the US: http://www.magnaplate.com/coatings/tufram.html
In the UK: http://www.poeton.co.uk/w1/a350.htm