cutting internal pipe threads on cnc lathe. should the minor diameter be kept constant or should the hole be cut with the taper of the thread. this would leave equal material for threads.

Bore the taper first.

Hi Mike Rainey nice to see you. Well it of to work for another night of paperwork-Boston Globe, NY. Post and some locals. Have a nice day

Thanks Mrainey, thats what the fellow at Kennametal said. Got any npt gages for sale?

You too, my friend.

If it's any help, Union Butterfield has taper pipe reamers in their standard product line.

Thanks Jay. I am machining these parts on a cnc lathe. Don.

also make sure your thread tool path is also on a taper. If you're using Cam software like Mastercam, you can select the pipe thread in the parameters when doing the toolpath. Cam software makes cnc programming a joke. I remember 12 years ago when I would program each line of code to make taper threads on a old Niles Lathe running a GE 1050 control. The machine is older than I am LOL

I've got a question for you, its related but.. un-related.

Anyone know how to lay out pipe lengths when threading them together? I'm working on a piping project and am trying to get as much detail as I can but don't know how to figure out how much one pipe is going to thread into another and therefore be able to adjust its length accordingly. Anyone have some handy dandy rules of thumb for doing this?

Jerry [sorry if this is a bit of a hijack.. :(]

Usually Pipe Thread Wll Gage On 3-4 Turns. Eg 11.5 Tpi =.087 Per Turn. 3-4 Turns Would Be .261 To .348 Inches.or You Can Get Machinists Handbook Out And Look At Engagement Lengths On Chart.

I'll have to look at the handbook. I follow you.. to a point.. I'm not sure how to know at what point on the thread does it engage.. and then take X number of more turns.. kind of a black art as far as I can tell :)

Jerry

. kind of a black art as far as I can tell :) Jerry

It depends on the pipe you are using; if it is gas pipe it is black art but for water you need galvanized art. :stickpoke

And 150# steam pipe? seriously though... its 1 1/2" "black" pipe... I'm pretty much faced w/ put it together and then mark down the sizes for the next time..

Jerry..

O.K., so somebody please explain what I'm missing here. So even though you're machining on a cnc lathe, doesn't it still have a turret in which you could mount a reamer? And wouldn't that be easier and quicker than boring the taper? Or is something like this a case of not enough parts to justify new tools? :confused:

Reaming the taper would be slower and more costly if you don't already own that taper reamer. Boring it would definitely be the best way.

Jerry, are you trying to couple 2 pipes using a collar? If you're machining all the parts yourself I would follow the machinist handbook. If you’re buying parts off the shelf and trying to figure out lengths I wouldn't go by the book because most of the pipe thread elbows, couplers etc are coming from China these days and the quality control is not there. Do a dry fit in that case and measure the depths if it needs to be ultra precise.

Yeah, you could use a reamer if you had one. It will take about 2 seconds to bore. The NPT is a 1" 11-1/2. Thanks.

Pimp, no I'm actually just using 'off-the-shelf' stuff to design a water pipe,fuel and steam piping. I've not designed piping to this level before so.. its a learning experiance in itself. I'm trying to map out as much of the process as I can to simplify ordering and assembly. I can do just the mechanical layout and let a pipe fitter do the rest, but I've been asked to do what the pipe fitter would do, in figuring out all the fittings and the needed pipe lengths before we start. We're making several [like 18] of these system's so we want it to be kinda 'cut and paste' for each one.. I might just end up doing a prototype for the first one.. and then using those numbers to order for the following 17 units.

Jerry

... but I've been asked to do what the pipe fitter would do, in figuring out all the fittings and the needed pipe lengths before we start. We're making several [like 18] of these system's so we want it to be kinda 'cut and paste' for each one.. I might just end up doing a prototype for the first one.. and then using those numbers to order for the following 17 units. Jerry

Jerry this is high risk. As you know pipe threads are tapered and you cannot predict exactly where they will pull up tight. Also if one pipe fitter is a little guy and another is a gorilla you can get a turn or two difference on each joint. I suggest you identify locations in the piping network where you can simply spec out a nominal lengths and have these cut and threaded on site to accommodate accumulative errors. Probably at the locations where you put unions.

Thanks Geof.. thats pretty much what I've done already.. but was hoping the 'black art' ..wasn't.. :).. anyway I'll get most of it close and then we'll have to just 'as build' about 5 pc's each time to make it work.. I haven't found a way around it at this point.. it has to fit several lazer cut holes in the shack's and like you say.. it's probably not going to go together exactly the same each time anyway.. oh well.. it was worth asking.. this way I have a leg to stand on when I go back to my higher ups and say.. 'not gonna happen' :D

Thanks guy's.. I'll bow out of your thread.. and let ya'll continue..

Sorry for the temporary hijack.. :(

Jerry