Using a die to cut a thread on brass/copper pipe.

[Brian JohnParticipant @brianjohn93961]

UPDATE : My new heavier vice with the V notches arrived so I have put the brass tube in that and tried again. Still no luck as the tube keeps turning. I have got about two turns of thread cut on the tube but I cannot get any more. I am not sure what to try next. I was really not expecting to have any problems using dies : I thought using taps would be the big problem. I must be doing something wrong as some people said I should not need a vice at all ?

Edited By Brian John on 12/05/2014 06:11:22

[JasonBModerator @jasonb]

Brian do you have any other material that is 3/16dia? if you tried threading a bit of bar that would at least eliminate the copper from the equasion if it threaded OK.

[Brian JohnParticipant @brianjohn93961]

I am threading the brass tube. I have given up on the copper altogether ! Can this really be done by hand ie. without using a vice ? If that is so, then I am doing something very wrong.

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

Given that the depth of thread at 40tpi is only about 16thou … Yes, I would have thought it possible.

… I would guess that the die is undersize and/or not sharp.

Any chance you could post some close-up photos of the die, and your results with it ?

MichaelG.

.

P.S.

It might be worth acquiring some "surplus" knitting needles, in a range of sizes around 3/16" and finding out how small you need to go before you CAN cut a thread with that die.

Edited By Michael Gilligan on 12/05/2014 11:10:26

[stan pearson 1Participant @stanpearson1]

Hi Brian

Went into my workshop tonight and threaded a piece of 3/16 OD copper tube. The die is also from Tracy Tools and the pipe held in a 4" Record vice no problem. I think ether the pipe OD is not 3/16 or the die is not the correct size or you are not opening it out far enough with the centre screw.

Regards

Stan

[julian atkinsParticipant @julianatkins58923]

a possibility is that there is a burr on the die where the screws are supposed to engage, and on the split. i have had to remove same off quite a few dies using an oilstone. the other possibility is that the screw for the split in the die (in the die holder) hasnt got a long enough thread on it and isnt totally enlarging the die.

just a few off the wall thoughts from experience.

cheers,

julian

[Brian JohnParticipant @brianjohn93961]

Tomorrow, I will try enlarging the die with the centre screw and have another go. I did not think that the centre screw would enlarge the die enough to make any difference but obviously it does.

Edited By Brian John on 13/05/2014 06:02:11

[Rick Kirkland 1Participant @rickkirkland1]

Brian, you are right in thinking the centre screw makes that much difference. In fact on a decent quality split die the adjusting screws can make a difference between a thread which is too large to enter the nut and one which is too small to be of any usefull mechanical strength and all this without causing the die to break in two. Cheap dies are sometimes not even hardened let alone tempered for correct use and I have known them to have no relief whatsoever thus causing binding problems and chewed up threads.

Rick

[Gordon WParticipant @gordonw]

Have you checked the clearance of o/d of die to i/d of the holder ? I've had holders that would not allow the die to expand,. die o/ds and holder i/ds do seem to vary. Apologies if I'm beeing simplistic.

[thomas oliver 2Participant @thomasoliver2]

Thank you Rick for confirming what I posted – that it is possible to be sold dies either unhardened or with no rekief. It seems that since no approaches have given results, it is simply that the die has no relief and will simply not cut under any circumstances. The cure is either to grind in the relief, or to obtain a new die, preferably of British make. It is possible to cut good threads on copper pipe with a sharp die and some lubrication.

[Brian JohnParticipant @brianjohn93961]

Success…I think ! I opened the die out as much as I could using the centre screw. I was still having problems with the brass tube turning in the vice but I persevered by turning the die stock back and forwards about 10 degrees left and right ( a see sawing movement). Eventually, things became easier. I overdid it a bit as you can see : far too many threads

I think all my problems were caused by incorrectly fitting the die to the diestock the first time. As others pointed out, the centre screw was in the wrong place and this closed the die up too much.

1. Is that new vice okay ? As you can see from the top view the red base is not quite parallel with the jaws. I am not sure if this affects its grip ?

2. I have put a machined ell piece ( by PM Research) on the brass tube but it only goes on about two full turns. This seems to be the norm when buying machined parts as I have tested some of their other fittings with each other. These are straight pipe, not MTP. I thought they should screw on further than that ?

3. How do you clean all the filings from the die once you have finished with it ?

 

Edited By Brian John on 14/05/2014 06:04:23

Edited By Brian John on 14/05/2014 06:08:24

[Michael GilliganParticipant @michaelgilligan61133]

It looks like you are making progress now, Brian; although I would have expected the pipe to screw further into the fitting [perhaps six threads?]

If you now loosen the centre screw a little, and tighten the outer pair, it will reduce the diameter of your thread.

I see that the fittings are made to the Unified form [60°], whereas your ME Die would be Whitworth form [55°]. … This should be no problem, so it's probably just that your thread is a couple of thou' oversize. You have plenty of thread on your test-piece, so have a go.

MichaelG.

[JasonBModerator @jasonb]

As I said somewhere before in one of your threads I find that even PMR's "universal" thread does not fit ME despite what it says on their site.

First I would run your 3/16x40ME plug tap into the supplied fittings, if things are still tight then do as Michael suggests and loosen ctr screw and nip up teh outer ones and run the dia down the thread again.

J

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

Could you please measure the outside diameter of that thread that you have cut.

It may be an illusion, but it looks considerably smaller than the OD of the pipe … which would explain why you are having difficulty cutting it, but not why it doesn't screw into the fitting.

Dreadful thought: are you certain that the fitting is 40tpi ?

MichaelG.

[Brian JohnParticipant @brianjohn93961]

Outside diameter of the pipe = 4.73mm

Outside diameter of the thread = 4.59 to 4.64 (It varies according to where I measure it. I think this would be caused by making adjustments to the centre screw.)

[Brian JohnParticipant @brianjohn93961]

After initially placing the order for the carbon taps and dies with Tracy Tools, I reconsidered ; then I called them back two hours later to change the order to HSS but the carbon taps and dies had already been posted !

[Bob Brown 1Participant @bobbrown1]

Age old "pay for what you get".

In a production environment taps and dies are specified for the material they are cutting.

Personally from past experience I stick to the best I can get for a reasonable price and always in at least a HSS and prefer of they are coated but that adds another dimension to taps and dies.

Bob.

[Brian JohnParticipant @brianjohn93961]

I will be ordering some HSS taps and dies next time I place an order with Tracy Tools. In the mean time, I am still experimenting with the carbon dies. I have cut another thread on one end of a 25mm piece of pipe. My biggest problem is stopping the pipe from turning so the vice has to be screwed up VERY tightly. The vice I am using has V notches so that does help. But how do I cut a thread on the other end of the pipe as putting the already-cut thread end in the vice will crush that thread ?

[Boiler BriParticipant @boilerbri]

Hi Brian make two nuts. Put them on the threaded end and lock them together. You can then hold the job on the nuts.

Bri

[Brian JohnParticipant @brianjohn93961]

Yes, that sounds good. Thank you for the idea. I hope the taps cut better than the dies !

AFTERTHOUGHT : the nut will end up so tight that getting it off may be difficult ?

Edited By Brian John on 21/05/2014 07:31:32

[Brian JohnParticipant @brianjohn93961]

UPDATE : I ordered some HSS dies from Tracy Tools and they arrived yesterday. I have just finished cutting a 3/16-40 thread on some brass pipe : no fuss, no problems, no drama ! The HSS die did the job in minutes.

Forget all about carbon steel dies and always buy HSS.

Edited By Brian John on 03/07/2014 04:40:25

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 03/07/2014 04:39:51:

I have just finished cutting a 3/16-40 thread on some brass pipe : no fuss, no problems, no drama ! The HSS die did the job in minutes.

.

Great News, Brian … glad to hear it.

MichaelG.

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