So I chucked up a piece of 3/8" unthreaded brass pipe in the old lathe
and proceeded to thread it with a pipe die.
The die did a good job for about half the needed thread length. Then
the pipe workpiece stalled as the chuck spun on it.
I cinched it down and tried again. I got about a quarter turn more on
the threads only to have the chuck spin on the workpiece once again.
Well, ultimately I got the threads cut but the pipe was pretty much
The lathe seemed to have enough horse power to cut the threads - if I
could keep the chuck secured to the workpiece.
So what would you do (short of buying a new chuck) to keep the
workpiece and chuck acting as one?
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).
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.
collets have less holding power than a 3-jaw chuck, as chuck jaws bite into
collets are good for precision work, rapid loading/unloading of the
workpiece, or when you don't want the work marred
| 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.
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.
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
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.
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.