Soldering Aluminum? Good, Bad, Ugly??

[Chitownmachine]

So, I need to soldier a joint which consists of an 3/32" aluminum tube, inserted into a 3/32" hole in an aluminum head. Is soldering the way to go, or should I press fit? Oh yeah, and it needs to hold an air pressure of 50-60 PSI. I asked my welding professor and he suggested TIG, which on a really tiny hole like that, may be a bit over kill and he would do it in trade (ie 6er of beer) So any suggestions on where an at home kinda guy can do this type of joining? Thanks for the info!

 

[GailInNM]

Chi...,
Soldering is probably not the way to go. None of the aluminum solders will wick or flow into the joint. About the best you could do with solder is to build a fillet up around the joint. This is very difficult to do and have a neat looking joint. Also the difference in the bass of the head and tubing will make heat control difficult. Heat control is critical with aluminum soldering. The zinc base aluminum solders working point is only a few hundred degrees below the melting point of aluminum. I have not had very good results with other types of aluminum solder.

If you are using hobby store aluminum tubing, ie K&S, then the tubing is too soft to be able to get a good press fit.

There are several other ways to make the joint, but we need a little bit more information to be able to recommend one.

How deep can the tube insert into the head?
Does the hole for the tube pass through the head?
How thick is the head?

Gail in NM

 

[tel]

Twere me I think I'd be screwing the two parts together - 7BA or something close to it.

 

[Omnimill]

Have a look here:

http://technoweld-fusion.com/Int/TW_En/index.html

Vic.

 

[b.lindsey]

I agree with tel as to a threaded connection if possible, but if the hole in the head is already 3/32 that won't work unless you can use larger tubing. If the depth of the tubing in the head is sufficient and assuming the connection only needs to withstand air pressure and not steam or higher temps. there is a good possibility that a loctite connection would work too.

Bill

 

[shred]

Yeah, I'd be thinking about Loctite green sleeve retainer unless you needed to run high-temperatures

 

[rake60]

I've had very good luck with DuraFix rods.

http://www.homemodelenginemachinist.com/index.php?topic=1523.0

Rick

 

[bentprop]

Neither Technoweld nor Durafix will work on a 3/32 tube.
By the time you would get the head hot enough for the rod to flow,the tube would have melted into a globby mess.
I have used this type of rod for years,and it will not work in this situation.I would stick with a retaining compound on something this small.

 

[ruzzie]

Loctite would be my choice

680 Loctite - cured strength 3000-5000 psi working temp up to 150c
620 Loctite - cured strength 3000-3500 psi working temp up to 230c (450F)

Cheers
Paul