Fittings for a Stainless Steel Pipe

Why not just use some 1/2 steel plate cut to shape and weld it? I might contact somebody that makes drive shafts for assistance or google drive shaft fabrication for a shop near your location.

Your Pipe ID is 146.2mm or so and 2 inch 150# flange OD is 152.4mm. You can use 2 inch flanges either after threading on the OD and matching thread on ID of the pipe or after machining the Pipe ID to 152.5 and insert the flange and weld it at the edges , or lock it from the sides.

Probably the simplest would be to make two plates with O.D. to fit inside the 6" pipe, and I.D. to fit over the 2" or 3" pipe. Conveyor pulleys are often made this way.

Perhaps this is the way to go, with a bolt or clevis pin to convey the torque. Thank you for the reply.

Drive shaft end flanges need to be welded on not screwed.

What are you building John?

The 6" pipe will wind a cable of a boat lift.

What are the pros and cons of welding vs screwing?

You are building a capstan/drum winch.

Welds can't loosen ie unscrew.

If screw together is easier for you for what ever reason then you will have to tack weld the threads so they don't unscrew. If you need to dismantle you can grind the tacks off and unscrew.

With welding you aren't constrained to available thread sizes and possible design compromises. You can make it the size you want not the size that's available.

How about Tornado's solution, which involves two annular rings (he calls them plates) that fit between the two pipes. The pipes and the rings can be through bolted to make them rotate together. I do not know the cost of making those rings, however, and that can change the picture.

Bolt through would work but may clash with other parts. This method of securing is prone to hole elongation and increased lash over time...could even break the bolts if they wear thin.

A clevis pin would keep things turning together securely with easy dismantling but you will have to get keyways milled into the shafts and collars.

I haven't quite pictured the arrangement. Can you post a sketch?

The problem of hole elongation and lash could be reduced by increasing the diameter of the bolt. Here is what I now have in mind. The sketch shows just one end of the drum. The main question with this, I think, is the cost of the ring. Any thoughts?

Cost to fabricate (turn) the ring?

In these parts $10 labour plus material at metal spot price.

Well that is right on, Guru. Thank you.

Of course I must adjust for "in these parts," to "in my parts" since I see that you are in Phnom Penh and I am in Florida. How many machining hours are in the $10. labour? I can easily adjust hours to local rates.

If this goes into production, of course, I may be back in "your parts" again.

Machine shop here charges per job not time.

Not including shopping time for material that would take an hour or 2 to turn on a lathe.

Thanks to you and to all the others who have contributed to this discussion.

Why not make the outer part an interference fit on the inner part, then heat it, insert the inner part and let it cool? The process is called shrink-fitting.