lathe

[256]

I always wanted a nice used lathe to learn pipe threading and tapering etc. I am new to machining but know the basics.My employer has a good full machine shop to make drill pipe. What smaller but not too small used rig would you recommend for me to buy??. It needs to be automated only to the extent that the tool carriage and the chuck
are synced and move with each other.For making threads. I would guess most of them do that much.I want to spend about 5-800$.Dont care if its beat looking..
I want to start with plastic and learn and then move to steel. I want to learn first threading pipes and tapering and go from there..

 

[tweinke]

I think to do pipe threads you would also need a taper attachment.

 

[mmcmdl]

It needs to be automated only to the extent that the tool carriage and the chuck
are synced and move with each other.For making threads. I would guess most of them do that much

As stated above . You would need either a taper attachment , tracer attachment OR a cnc machine for taper pipe threads . Also , if you plan on doing any kind of true ( large ) pipe threading , you should go with at least a 15" swing with a big thru spindle bore . JMI .

 

[Downunder Bob]

As above, firstly what size pipe do you want to work on? you will need to get a lathe that will accept that size through the spindle bore so could be a quite large machine. Unless you simply want to learn the threading process on short pieces of pipe, that can be fitted into the chuck,then a smaller machine would work.

Also, as mentioned above you will need a taper attachment if you want to make taper threads, they are not usually cheap. however again if you are really only wanting to learn the process of thread cutting on a lathe then any lathe with a leadscrew and suitable change gears or gearbox will suffice.
Good luck, and have fun.

 

[256]

what specific machines would you look for?

 

[Bob Korves]

If it is just threading pipe that you are interested in, then I would buy a pipe threading machine. Tapered pipe threads on a lathe can be done with a taper attachment, but setting it up properly takes too long unless you will be doing larger quantities, which brings us back to a pipe threading machine, or if you are a hobbyist and time is not an issue. You can also use dies for cutting pipe threads in the lathe, but often to less than perfect pipe threads. A lot of it depends on whether the threads will be used for holding pressure or not. If not, there are more options for methods that will work adequately.

Of course, a good lathe can do lots of different jobs, not just cutting threads on pipe.

 

[Bob Korves]

what specific machines would you look for?

Some lathes will not be equipped up from the factory to do some pipe threads, like 11 1/2 and 27 TPI. If the threads need to be tapered, then a taper attachment will be needed. The hole through the spindle must be capable of letting the size pipe you want to cut through it. The lathe must be in good condition and properly set up if the threads will need to hold pressure, which requires accuracy to ANSI/ASME standard B1.20.1, that would be if you want to sell them commercially.

 

[P. Waller]

I have found turning taper pipe threads on a manual lathe with a conventional taper attachment to be about as slow and annoying as lathe work gets.

I suspect that there are oil field lathes with provisions for doing such work on a production level that are not NC.

However if you have many parts of different sizes to produce a NC lathe wins.

 

[Bi11Hudson]

Pipe thread is tapered. It must be cut with a taper attachment, the compound won't work. Conduit thread on the other hand, is not tapered. It can be cut on any machine that that will cut the particular thread. And, pipe thread in the smaller sizes is sometimes fractional or an odd number, as noted.

For cutting pipe(tapered) thread, a die is probably the better choice. Unless it is for a spaceship or something of that nature. A pressure connection should be run in under fairly heavy torque anyway, so accuracy of the thread is usually not a big issue. Optionally, an insert from a pipe die could be set into the tool holder if the particular thread were available to use. That would cut the tapered thread, but would be a heavy load on most any machine unless you made multiple passes.

Conduit(straight) thread is permitted, by the electrical code to be cut with a pipe die. I usually loosen(?) the cutters a fuzz so it cuts a little oversize, but that's optional. So long as the fitting will pass over the thread. There are places where the conduit thread must be a couple of inches longer than pipe thread, so part of it ends up straight anyway.

Further, as noted, the pipe should be able to pass through the headstock for any usable length. For anything over 1/2" pipe, that involves a full sized machine. Over 3/4", you're talking big bucks. The only exception there(literally) is for a short(close) nipple. What must be kept in mind here is that the 1/2" is nominal ID and requires almost a 7/8" hole to pass through. I use a Craftsman 12X36 with a MT-3 taper and my passthrough is limited to 3/4", too small for 3/4" pipe. So, you're talking a large machine from the git-go.

Bill Hudson​

 

[Bob Korves]

What must be kept in mind here is that the 1/2" is nominal ID and requires almost a 5/8" hole to pass through.

Bill, 1/2" NPT is .840" nominal O.D., larger than 3/4".