Slip & Slide

Use a collet. Much more surface bearing on the workpiece Simple solution for this project would be a Hex-shaped 5C collet holder in the 3-jaw, and 3/8 collet (assuming that dimension is the actual OD).

Perhaps a lathe dog and driver plate. Four jaws normally hold better than three. Was the die one that cuts a standard tapered pipe thread- and you wanted to cut longer thread than normal? Jim.

Try putting some paper, only one layer, around the pipe before chucking it up. Use regular white printer paper, not shiny magazine stuff or thin newspaper. It's possible that when you chuck up on the part that the back of the jaws are the only jaw surfaces touching the part if the chuck is worn. If that's the case then the paper trick might work better with two layers. Of course the jaws should be repaired if worn but sometimes we can't do what we want.

Oh yes, brass pipe is not very stiff.

You should not need that much HP. You need a sharp die and some cutting oil. Yes, cutting oil also helps on brass. Dies don't have a relief and brass is quite springy. The oil helps to reduce that friction.

HTH, Nick

are you sure that your die isn't a rethreader type with no relief? That would make cutting threads much more difficult

tony

collets have less holding power than a 3-jaw chuck, as chuck jaws bite into the work.

collets are good for precision work, rapid loading/unloading of the workpiece, or when you don't want the work marred

can you do the job off the lathe, using a chain vise? I never had a pipe slip in a Rigid chain vise/tripod. Or just use a Rigid pipe threader.

Sacrifice a bronze bushing. Find or size a bushing to the OD of the pipe. The longer the better. Saw cut through the wall. Now, chuck the assembly in the lathe with the saw cut between two jaws.

Better still is to use medium or course grit sand paper instead.

Answers to the questions: I was only cutting a standard length pipe tapered thread. The pipe was 3/8" pipe meaning it was 3/8" ID. The OD was whatever brass pipe is. The die was a Greenfield "little giant" 2 piece removable type - very old but seems to be sharp. I used steel tapping fluid as a lubricant. I don't have a chain vise or a traditional pipe threader.

Thanks for the sandpaper idea. I'll give it a try next time.

Gary

Don't know it this is true in your case, but I've sometimes had relatively thin walled tubing collapse slightly in a three-jaw chuck and then this collapsed area "rolls" as the work slips. The solution is to put a proper sized round pin inside the tubing so the jaws clamp the tube against the pin.

Jerry

Sure, but that's part of the problem.

The solution to this problem has already been posted. Turn a bushing as long as the chuck jaws. Turn its ID to slip over the pipe, then slit the bushing and use the chuck jaws to compress the bushing over the pipe. You ain't a'gonna do any better than that.

GWE

I've yet to see a 3-jaw chuck that holds stock anywhere near as well as a 5C collet does in its diameter range. If the chuck jaws are biting into the work for solid pieces, the chuck is being abused. If the chuck jaws bite into the work for hollow pieces (as in this case) the work is scrap.

Mark Rand RTFM