facing the end of a pipe

[ARC-170]

I have a 4.5" dia x 0.25" thick steel (type unknown, but it's nothing fancy) pipe I'd like to square the end on. I cut it with a reciprocating saw so it's a bit crooked. I grinded it down a bit. My question is how I should go about squaring it up on the lathe?

Here it is mounted on the chuck. You can see where I've tried to cut it:


Here is the cutter I'm attempting to use. It's cut like a cut-off tool:


I thought I might try using this cutter in this orientation when I get the end smoother:


Here is an end-view of the pipe:


I'm getting lots of chatter. The lathe is on low speed (164/500) on the spindles and medium speed (1140) on the motor. Back gear is not engaged. If the motor I have is similar to the original and I'm using the speed chart in the MOLO correctly, then I'm at 500 RPM. I tried it on low (164) and it really chattered. Higher speed gave a smoother cut.

Cutting speed for carbon steel is 80 ft/min. 3.82x80/4.5=67.91 RPM. I'd use the back gear drive for that speed, correct?

Because the end is crooked and the pipe wobbles a bit in the chuck, the cutter will contact the material, then be in the air, then contact the material, on so on. I've grinded it such that the tool doesn't contact a blunt end; instead, it contacts a "ramp"/inclined surface, but at some point, the cutter will break thru; then what? Whenever I've used a parting tool before, I've always stopped before it broke thru. I may not have that option here; it may break thru in one part.
Here's a sketch to illustrate what I'm talking about:


One option may be to grind this down as square as I can, then finish it on the lathe. However, it's a lot of grinding. I thought using a cut-off type tool would be quicker and look nicer. I didn't count on the pipe wobbling, either, but didn't think that would matter since I don't need the end perfect, just somewhat smooth and straight.

I'd like some guidance on how to safely do this. Thanks!

 

[matthewsx]

I just did something similar today but with a much smaller tube. You will need to get it chucked up with as little runout as possible, I had to file and sand the end I planned on cutting so I could use a dial indicator to get it aligned. Then light taps with a small hammer should allow you to true it up. I used a rounded HSS bit and cut back from the center with the tool at ~29*.

I'm sure someone else has a better insight but that's what I did and it worked for me.

Cheers,

JOhn

 

[mattthemuppet2]

smack it a bit until it's running true, put the lathe in backgear then use a RH cutter (like the brazed carbide cutter in your 2nd pic) to face it with the carriage locked to the ways. I'd start off with light cuts otherwise the interrupted cut will lever the pipe out of the chuck.

If you want to hold it a little more solidly, hold it in a 4 jaw, that'll be a little more secure than a 3 jaw.

 

[T Bredehoft]

John has it right. Before you cut, get the outer surface of the meterial running without wobble, to be consentric. Then cut toward the center, a bit at a time. use, under 100 RPM, slow to get the correct surface feed. Until you have one continuous cut you must take so little cut that it doesn't disturb the security of the piece in the chuck.

 

[ARC-170]

Thanks for the input! Just to clarify:

1. Use a hammer and dial indicator to get the pipe running true. Light taps.

2. Use the RH cutter or a rounded cutter to cut from the center of the pipe out. In other words, cut away from the center and toward me. Take light cuts until the cut is continuous.

3. Cutter bit should be angled a bit in relation to the pipe. In other words, don't cut with the whole length of the cutter (as shown in 3rd picture above), cut with the point.

4. Lower speed. Use back gear.

 

[markba633csi]

Agree with all above. Always risky when you hang a workpiece out farther than the diameter, but we all do it and (usually) survive to tell the tale.
Be careful, try to stand off to the side somewhat in case the pipe decides to fly out in your direction

 

[ARC-170]

Agree with all above. Always risky when you hang a workpiece out farther than the diameter, but we all do it and (usually) survive to tell the tale.
Be careful, try to stand off to the side somewhat in case the pipe decides to fly out in your direction

Thanks! It's already come off once. It was very slow speed, so it was fine. I think the bits are dull as well.

 

[MontanaLon]

Run your tail stock up and extend the quill inside the pipe so if it does come out of the jaws it can’t get loose and create chaos.

 

[MontanaLon]

Also, if you turn down the thickness away from the ragged edge the interrupted cut will be less of an issue as the thickness isn’t so great.

interrupted face cuts place a tremendous amount strain on everything where interrupted turning cuts are less stressful.

 

[benmychree]

If you were doing this very much, I would make a "spider", a steel disc that would fit inside the pipe with perhaps 1" total clearance, with 4 holes tapped into it radially for 3/8' square head setscrews, on the back of it I would weld on a piece of pipe that would fit through the spindle with cross drilled holes that would mount a pin at various distances that would bear against the spindle end so that tailstock thrust would not push it back, and of course, on the front end there would be a center drilled hole (in the center) for the tailstock center. In use, it sits inside the pipe enough to clear the tools used for facing or parting, and would be used to center the part up, much like a 4 jaw chuck. This is standard shop practice, often used. As you have already seen, it is all too easy to knock long unsupported work out of the chuck. As to extending the tailstock into the work to prevent the work being tossed out at long range, why risk scarring up your tailstock quill?