Ok...so I need some help. Although I am not new to the industry, I have never tried to cut threads in aluminum pipe. I am wiring a new grain bin and using aluminum pipe. It is great to work with.....well it was until I had to cut and thread it.

Can anyone one give me any pointers on how to thread this stuff? What do I need to use for a threading compound? I can cut the threads ok but when I go to back off the die, the cuttings get bound up in the threads and destroy what I just cut. Help....please!

Thanks, Merlin

Sure .... prepare to forget everything you think you know about pipe!

First off, aluminum is considerably softer, weaker, and -paradoxically - a lot less forgiving than steel. You'll have to take considerable care not to crush or fltten it in your vise, when bending it ... and you can forget about 'unbending' it if you make a goof.

Wear gloves - the oils in your hands will oxidize the aluminum, and turn your skin black.

As for cutting threads, go to a machine shop supply house, or visit one online, like MSC Direct. You'll want to use a water-based cutting fluid - I reccomend LPS Green - rather than the usual threading oils.

Once you thread something tight in aluminum, you can forget about loosening it; you'll usually destroy the threads. It's probably a real good idea to use Noalox on the fittings for this reason.

Thanks, Reno. So can I use regular pipe threading dies or do I need special dies?

Regular dies are just fine .... just pay attention to the chips, and back the dies off several times to break the chips. Be wary of the chips as well, as they will iterally be razor sharp.

Thanks for your help. I tried a different set of dies and they worked much better. I must of had a dull die that was causing me some aggravation. I actually used WD-40 for lube and it worked great. Thanks again for the info.

The problem with cutting near pure aluminum is that it's so soft. You need an acute rake angle on cutting tools to get them to penetrate properly, and a standard die set will usually be set up for steel. That usually means they cut oversize first pass. Reno's answer of a cutting 'gunk' plus cycling the die down is the solution. Aluminum also tends to 'gall' or weld itself to cutting edges, so it's advisable to check and clean any galls off regularly.

Got to go with Reno. The new set of dies will be a big help too.

I seem to remember that the manual pipe threader in our fitting shop withdrew the 4[?] dies once you got to depth, so you did not have to unscrew the pipe to get it out.

Alan.,

Yes I did recall in the Ridge companie they did have one like that and it have special cam on it when you get done threading the alum pipe then hit the lever which it will pull the dies out then you can slide it out but becarefull it don't take much to nick it.

But as other mention a new die and diffrent cutting fluid will work just fine.

Merci.
Marc

You won't believe this, but we used lard!

I have heard that one and myself I haven't try it yet.

Merci.
Marc

Lard is a great cutting lube, active ingredient is lard oil, [olein], which is sold commercialy as a cutting fluid. Our foreman Frank used to mix it with kerosene, 50-50 when I was an apprentice for machining dural. Mineral oils don't make good cutting lubes for soft metals like aluminum or copper as they seem to flow away from the action.
I have seen soap/water and even gasoline [ ] used to machine soft copper, and even had one guy who reckoned milk was the answer- till it went off in his suds tray! Nothing quite as permanent and truly obnoxious as really rotten milk!

Point is, these items are all at the supermart and I bet they are a tenth of the price of fancy cutting oils.