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coollx
11-05-2005, 10:09 AM
I have a project I'm working on that requires various ID's and want to use 4" schedule 40 PVC plastic pipe as the basis. As manufacturered it has a 4 1/2" OD and a 4" ID. I want to make several versions of it with different ID's and thought boring it or possibly turning it would be a way to accomplish it.

Being a very very amateur home shop machinist my problem is I do not know how to accomplish it. I have a 9" X 20" lathe and a BP mill but have not been able to figure out how to hold the piece on the mill or chuck it on the lathe.

I don't have a boring head for my mill but would buy an inexpensive one if I could figure out how to hold and center the work piece. By the way, the workpiece will be between 4"-5" in length.

Any suggestions and help would be greatly appreciated.

Thanks

Dom

punkinracer
11-05-2005, 10:23 AM
Well if it were me I would machine up a blank of material to same ID as the standard pipe, put the pipe over it and chuck the whole lot in the lathe. That way the pipe won't get squished when tightening the chuck.

HTH,Pat

Evan
11-05-2005, 11:19 AM
Yep, I make stuff from PVC pipe all the time. Make up a plug for the sizes you want to hold or if you are going to hold on the ID then make a metal or wood collar for the tube. When boring with a boring bar which I do when putting non reflective threads on the inside (spotting scope etc) it must be very secure and perfectly centered or it will snag and throw it out of the chuck. Be prepared for a few little incidents like this and keep one hand near the OFF switch.

darryl
11-05-2005, 02:36 PM
It's pretty easy for a cutter to snag in pvc and rip the piece out of the chuck. Just something to be careful about.

I second the use of a turned plug, but I would add that the id of most pipe is not round to start with. You might want to true up the id of one end of the piece, then turn a second plug for that end, and begin the part you're making from that point. Depends on how accurate the end result needs to be. Releasing the part from the chuck will likely let it flex back into a non-round shape internally if you don't take this extra step.

coollx
11-08-2005, 07:17 PM
I do not currently have a chuck large enough to grip the OD of the work piece and wonder if the following might work.

Turn a wood plug the size of the PVC pipe ID that's about 2" long. I would turn it by drilling a hole in the center of the wood blank then holding it tightly to the chuck with a bolt. Epoxy it in one end of a piece of the PVC pipe that's 2 inches longer than the finished work piece. Hold the PVC pipe with plug epoxied in place to the chuck with the nut and bolt used to turn the plug. Then bore the ID of the other end of the pipe to the desired size. When done, cut the plug end off.

By the way, the finished ID does not have to be super precise.

Will it work? Will epoxy hold wood and PVC together?

MarkT
11-08-2005, 08:26 PM
As an alternative have you considered just heating it up and stretching it out? The link below talks about reforming pvc. If you could heat it evenly enough you should just be able to pull a properly sized ball through the piece. I haven't tried it of course, but if it doesn't kill you outright it might work.

http://billpentz.com//woodworking/pvc.html

coollx
11-08-2005, 08:42 PM
MarkT, interesting article. However, for this particular project, I need to maintain the OD while increasing the size of the ID.

Thanks

darryl
11-09-2005, 12:02 AM
Dom, you could always bore a hole in the wood piece large enough to fit over the outside of the jaws, then crank the jaws out to grip the wood. Turn the wood for a tight fit into the pipe. Then mark the jaw positions on the wood so you can return the wood back to the chuck the same way. Remove, saw a slit through this 'doughnut', then compress it slightly to fit it into the pipe. Return it to the chuck and make a few trial turns of the spindle by hand to check for runout of the pipe. Tighten the jaws outwards in a few steps while aligning the pipe. With the slit in the wooden doughnut, the jaws' force will transfer to the pipe ID.

I don't like the bolt idea- done that lots. In no time the disc will be turning off-center. What you could do though is put a threaded rod through the spindle, and arrange to hold the wooden piece tightly towards the chuck, drawbar style. You night need to make a large wooden washer to facilitate this, and maybe arrange for the threaded rod to remain centered in the spindle bore.

Is the diameter of the chuck larger than the diameter of the pipe? If so, you can press the pipe against the chuck as you're tightening it, and that will help to keep it running true. If the chuck's OD is smaller than the pipe's ID, then you can slip most of the pipe over the chuck, and there won't be so much overhang when you go to machine on it.

By the way, it pays to stop often and clear the stringy ratsnest of cuttings. If you don't, it can whip up into a huge car-wash-like brush that wants to sweep out and rip your lips off.

Epoxy- I'm not too sure about using that to hold pvc. If you rough sand the area to be glued, that should hold ok, but don't rely on that too much. Expect the pipe to go flying at any time anyway, because there's enough flex in it that a snagged tool could easily rip the pipe out and throw it. Been there many times. Go with the wooden disk idea, and maybe put a few screws through the outside of the pipe into the wood.

darryl
11-09-2005, 12:06 AM
Oh, I meant to say as well that instead of a single hole bored in the wood disk, you could have three holes in a triangular array. One jaw fits each hole. That system has worked well for me. Or if you wanted to get creative, you could go with the single hole, but bore it in two steps such that it fits the steps on the jaws. That way more jaw surface is holding against the wood.

[This message has been edited by darryl (edited 11-09-2005).]