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spro wrote:Tapered threads can "bottom" out in certain fittings or even pipe clamp heads. The "tightness" should be within the thread taper and not because the minor diameter went too far and bound.
Exactly. Correctly cut, the end 3 threads of the pipe are full and sharp and are responsible for sealing the joint. If the thread is loose and the end of the pipe binds against the fitting body then they don't make full, tight engagement with the female threads and the joint leaks via the incomplete thread crests that follow. After the first 3 sealing threads, the remainder are just there for mechanical strength of the joint. It is important not to overtighten even a correctly cut threaded joint. 1 to 2 turns past hand-tight is sufficient; overtightening just serves to distort the threads and may drive the sealing threads in past the last thread in the fitting.
Not an issue with the pipe clamp scenario, but useful information if you ever decide to use your tools to do a little plumbing.
I've done this a bunch of times over the years. It's no big deal if it's for clamps. Not like it will have to handle 150 psi.
Clamp pipe in your 'average sized' bench vise.
Get a 'decent sized' pipe wrench to help it stop from turning.
Slap appropriate sized die in die holder and put on pipe
Lube with whatever oily liquid you have around
Thread it. Maybe have to reverse threader to break chips every so often.
Wipe clean.
Done.
Elapsed time 3 minutes.
I've threaded a couple kazillion miles of 1" & 2" schd 40 pipe, with Ridgid electric machine, hand held....model 700 if I remember right.
I've also threaded at least one kazillion miles with a 12R hand ratchet and an 18" pipe wrench for a vise. 12R used the same dies as the electric threader.
No difference in quality of threads between the two, and we often pumped water above 1000 psi.
(All is well if the dies are sharp.....and don't spare on the dope.....)
The only difference..... that hand ratchet was a whole lot like work!
I had to tap a pipe thread in a PVC end cap and I was VERY surprised at how fast the cutting forces went up as I went in. I may bore the hole tapered next time to make it easier. This is not a pressure-critical application.
SteveM wrote:I had to tap a pipe thread in a PVC end cap and I was VERY surprised at how fast the cutting forces went up as I went in. I may bore the hole tapered next time to make it easier. This is not a pressure-critical application.
Steve
Would ABS work next time? My experience with the ABS and PVC has been that ABS is a harder plastic and cuts with less force, the PVC seems to be softer and more 'gummy' providing higher friction between the pipe and cutter.
