Threading Schedule 80 PVC Pipe

[sunworksco]

I am searching for information how to thread the inside diameter of 4" schedule 80 pvc pipe which has a wall thickness of .337".The female thread needs to be a coarse and straight.I am also needing a threaded male plug with an o-ring for sealing the pipe.This project will be used for a scuba water tight container.
Thanks,
John

[Marklar89]

Isn't there a clean-out adapter that works for sched. 80? If so that would be the threaded fitting, the cap, and the o-ring together. Should be what you need. Maybe a sched 40 clean-out would work too, but I doubt it because of the differing wall thickness, unless the outside diameters are the same. It seems you need the strength of sched 80 though...

Lets see what others say.
Mark

[Fireguy97]

Originally Posted by sunworksco

I am searching for information how to thread the inside diameter of 4" schedule 80 pvc pipe which has a wall thickness of .337".The female thread needs to be a coarse and straight.I am also needing a threaded male plug with an o-ring for sealing the pipe.This project will be used for a scuba water tight container.
Thanks,
John

Will this be pressurized? I'm not sure if Sch80 is rated for pressurized air. PVC in general is not rated for air pressure. SCUBA denotes pressurized air. Water tight -is not pressurized.

If it's not pressurized, what about gluing a female adapter (slp x fip)? This would be a built in thread. Finding an O-ring that would fit shouldn't be that hard. If you are willing to go with a little bit of a buldge, you could use a union for the O-ring part.

If it is pressurized, I would find another material to use.

Mick

[PLUMBER RICK]

my very first underwater video camera i made with sch 40 5'' pvc. the control rods were brass toilet lift wires into 1/8'' brass compression fittings drill out to accept an o-ring.

the 2 halves were held together with a 5'' no hub band. my first 60' deep test was with no camera inside. worked all the controls and came up dry.

loaded my 8mm sony camera and was off to film the sea lions. we had fun blowing bubbles at each other and got some great shots of them underwater.

so if i can risk a $1000. camera on an o-ring, no hub band and pvc pipe, it can work. this was done in 1991 before i had access to a machine shop.

you can take the material to a good machine shop and they can thread the id, od and machine an o-ring grove into the plastic.

unless you know someone, a single custom job is not cheap.

buying parts off the shelf is cheap. male and female adapters with plugs or caps are cheap. sch. 80 fittings are much more than 40.

a good irrigation supply should have the fittings you need.

rick.

[lovetheUSA]

There is no standard thread for the inside of any pipe. As someone mentioned, a machine shop could thread the pipe, and would have to make a plug also, as there will be no standard fittings which would work

Machining a plug with an o-ring type of seal will be much better than relying on tapered threads.

[myakka]

You are going to have problems threading any plastic. You'll need a constant cooling source(flowing water or other) and something on the outside of the pipe to keep its size and location to the threader constant(assuming as you said you are threading the inside of the pipe).

[sunworksco]

I have been talking with some machinists about maching the inside threads of the 4" schedule 80 pipe and have come up with a single tooth cutting tool design that can be hand cranked and adjusted for depth control for several re-threads.I will be using a wooden mandrel with a pilot shaft hole through the center for the interior of the pipe with a no-hub coupling to couple the end of the pipe to the wooden mandrel.The other end of the pipe will have an Acme single tooth thread cutting tool mounted to a steel support disc mounted on an Acme threaded rod with a hand crank.The Acme threaded shaft will be free turning with female thread discs fastened on each end of the wooden mandrel.
This may sound like a lot of design and fabrication work but most of the parts are off the shelf and are easily assembled.I have been threading pipe for 40 years and I think that this threading tool is very practical.Most machinists that turn pvc are quoting me several hundred dollars to thread both ends of the inside diameter of the pipe,not including the threaded screw plugs.There is a similar scuba container used for flairs and gps devices rated at over 200ft. water depth and that is with slightly thicker wall than schedule 40 pvc.It is cast abs pipe with pvc screw plugs/o-rings,measuring 2-1/8" I.D x 9" long.

[PLUMBER RICK]

is you project a 1 shot deal or will you be making many of these.

as with anything else, the first one is time consuming and expensive. the next ones are cheap.

i'll show this to my buddy who has a cnc machine shop and he can quote you a price based on you specs.

please update your specs and is it a similar design to the one you posted?

how many do you need?

he's in los angeles and can get this done.

of course a photo/ shop drawing is good with dimensions.

rick.

[sunworksco]

These water tight containers are used for RC submarines.You can got to : www.subcommittee.com to see examples.
They vary in OD sizes of 2.5"-4.5" and range from 8"-36" in length.I have talked to numerous machinists that want to thread many tubes at a time but these wtcs are not flying out the door now so will have to machine by hand for now.

[sunworksco]

Submarine components.