"simple" AL to AL press fit cap

[Mantawa]

Hello,

I am looking for some guidance in specifying the dimensions for an easy to assemble press fit aluminum cap. The cap has a thin wall flange that will be pressed into the id of an aluminum tube. tube ID = 0.945in.

Any help is appreciated.

 

[vc66]

http://www.eng-tips.com/faqs.cfm?fid=1230

V

 

[drawoh]

Mantawa,

Please define "easy to assemble".

I do not think you can do a metal to metal press fit that does not require tools. You cannot take it apart easily, afterwards, without tools.

I once designed a metal to plastic press fit that could be assembled by hand. I used screws to keep it together. Another option is to use or design a snap fastener, or some kind of springy interface.

JHG

 

[MadMango]

Taking it apart may even be harder due to galling.

 

[drawoh]

MadMango,

You can control galling by specifying an anodize finish. The dimensional accuracy goes down, of course. Since it goes down, your nominal dimensions create more interference, increasing the nominal assembly force.

JHG

 

[Mantawa]

Thanks for the replies so far.

The assembly needs to be assembled easily, (simple press fixture at most). I'm not concerned with ease of disassembly. The parts will be anodized which will make controlling the fit more difficult.

A snap-together mate would be ideal. Does anyone have experience with snap together aluminum assemblies?

Thanks!

 

[drawoh]

Mantawa,

If it is a permanent assembly, you can specify the dimensions for an ANSI FN1 fit. This might be pretty accurate for anodized aluminium. This assumes of course, that you are machining it.

A snap-together assembly consists of a bunch of components that bend (strain) a lot. You need to understand exactly how your components are going to work, and how permanent they need to be. You need to do structural analysis. You need to feed your structural analysis back to your part design, and probably, work back and forth through a few iterations. You need to understand how your parts are going to be fabricated.

Search Machine Design Magazine online. They have done some articles on snap fasteners.

JHG

 

[tbuelna]

A thermal shrink fit would be easiest. You should be able to get at least .003 inch of interference fit with two aluminum parts and a 0.945 diameter.

Of course, you didn't mention what kind of forces the fit must be capable of sustaining.