Threading a 6" diameter aluminum tube

[psient]

Hi:

I own a PM 1340.

I am not sure if this is the appropriate place to post this. If not let me know. All dimensions are inches.

I have to create a canister made from aluminum tubing. The wall thickness is in excess of .378 and the O.D. is 6.25.

I will have to thread the O.D. using 8NPT. I have an indexable toolholder with a specific insert for this thread. The insert is specific to the toolholder (Seco/Snap-Tap).

How would you do your set up. I know that Aluminum is difficult to tread. I figure there is no better place than here to get advice.

Once again I apologize if I have overstepped the rules governing where this should be posted. I see no manufacturing discussion forum here.

Jon

 

[Th232]

Can't help you very much, but there's a machining section right here:

http://www.candlepowerforums.com/vb/forumdisplay.php?f=44

 

[DM51]

Moving this to MMM...

 

[precisionworks]

How would you do your set up.

Cutting NPT pipe threads is easy enough on steel, and even easier on aluminum.

NPT threads have a standard 60° thread angle, so your Seco threading insert should be perfect.

For 6" pipe, nominal OD is 6.625". Your aluminum pipe is 6.250". If you are using a standard 6" coupling it will be too large for your tubing. If you are making a custom coupling (or cap) you will not have a problem.

Set your taper attachment to 1° 47' (the taper is 1/16" in an inch, which is the same as 3/4" in a foot). Touch off the insert at the end of the pipe, advance the cross slide and make your first threading pass. Continue this process, advancing the insert each time until the thread is at proper depth. Here's an excellent reference chart: http://www.engineersedge.com/hardware/taper-pipe-threads.htm

No taper attachment? Take the piece to a shop that has one.

 

[gadget_lover]

Since the threads for NPT are not usually real long, wouldn't you be able to use your compound-slide? set to that same angle?

Never mind. As I visualized it, that will give you a taper, but not threads.

How about offsetting with the tailstock?

Daniel

 

[brickbat]

Another option for you if you don't have a taper attachment:

http://www.practicalmachinist.com/vb/general/cutting-npt-thread-manual-lathe-201212/#post1324512

 

[Torque1st]

If no taper attachment is available I would use a straight 12TPI thread and an O-Ring.

 

[precisionworks]

use a straight 12TPI thread and an O-Ring

+1

If you aren't holding pressurized gas or liquid, the straight thread plus O-ring does a nice job. Look at all the lights using that same method.

 

[Torque1st]

+1

If you aren't holding pressurized gas or liquid, the straight thread plus O-ring does a nice job. Look at all the lights using that same method.

It even works for pressurized gas and liquids.:thumbsup:

Tapered threads are frowned upon for any type of industrial system where leaks are to be avoided, hydraulics, pneumatics, process piping, controls, etc.