Lathe Steady Rest - Is This Kosher?

M

MTBob

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The other day I need to turn a long round bar of brass, about 2" in diameter, about 18" long. I first put a center finder scribe on the end, and center drilled it in the drill press. I didn't have a dog that would fit over the bar, so I stuck in a 6 jaw chuck and supported the end with a live center on the tail stock. I then turned a smoother surface on the bar for the steady rest to run. I noticed that the bar had some runout since the center I drilled wasn't exact. Got it all set up, and removed the tail stock support. (I wanted to machine a piece on the end of the bar and then part it off). So, as I was cutting the end I found the bar loose in the chuck. I tightened it and began turning again. Again, the bar came loose in the chuck. It seemed to work it's way out of the chuck.
So, here's my question - is it kosher to mount a bar in a chuck when using a steady rest? Or... was the bar becoming loose simply because I had a small amount of runout at the steady rest location?

MTBob
 
From the sound of it, there may be a few reasons: 1)the stock that's being held in the chuck is tapered, 2) the chuck jaws are tapered or 3) the stock isn't running true between centers and is in a bind in the steady rest. The steady rest may be slightly off center and binding the stock causing it to 'walk' out of the chuck jaws.
When you set the steady rest, did you hang the stock between centers, true it, then mount the rest while the tail stock was still in place? If not, chances are the steady rest is off center and pulling the stock.
I hope that makes sense.
 
Two things at play here. One is the soft nature of brass. That allowed the second factor to play more aggressively. You weren't quite on with your steady rest setting. It's natural for a workpiece to "walk" out of a chuck if the steady isn't set dead true. Since your center drill showed runout when you moved to the steady rest only, something is amiss. Of course, the tailstock is strong enough to pull the piece pretty true when you have a center in the stock, so you might not notice that it isn't aligned with the headstock perfectly. With the steady off center a little, and the material being soft, the jaws would work into the material and get loose. It's not so much the chuck backing off, but the jaw eating into the brass. With the bar floating, knock it around until running true. Stick an indicator on it and bring the steady to bear against it while watching that you don't push if off center with the tips. That will assure you that it is running true with the headstock.
 
Tony is correct. Also,brass is a slippery metal. Try wrapping a strip of brown paper bag(paper without clay in it) around the brass(1 layer only) and clamping the jaws onto the paper. But,the brass is wiggled with every revolution if it is a little out of true,and does want to walk out of the chuck.
 
Thanks folks, this is really helpful. I think just about everything you mentioned was at play with my set up. What I need to do is to use a dial indicator on the bar near the chuck and then align the bar near the steady rest with that indication. In addition to the alignment technique, you've told me that it is OK to use a steady rest with a chuck. I just wasn't sure about that. THANKS!
MTBob
 
Well, using a steady rest with a chuck is pretty standard. After all, a faceplate and a drive dog wouldn't work with it, so what other options are there that you might have? A collet? Sure, but most collet work is done up close, so I'm thinking that not many of us have used a collet with a steady rest.
 
Ok Mt Bob, Ya want to really get on the darkside. The other day this job requiring some
turning to a dia. and threading on a 4' X 2 1/2 Alum stock. First problem a freind borrowed
my tailstock chuck & and a center drill and thats like a MT 6 for my gk1918 so thats out and
of course they want this yesterday. So I got to do it on a SB9. I should but I dont have a
steady rest for either SBend, only a follow rest,and I need centers. On a four foot piece, ya
right. I called customer to know what was important, they said only about four inches each
end anywhere else not important. Once I drill both centers good to go. So I dialed in the
4jaw, dialed in the tailstock end to the follow rest and ran one of those swivel knurlers
right in there against the work to the follow rest. You know that worked so well I am
going to make brass rollers for the thing. I got plenty of knurlers. Who needs a steady rest.
Then the old twist of fate, no soon I got done here comes my borrowed Greaves chuck.
Then a little sandpaper on the knurl marks, nobodys the wiser.

gotta be a little red necked sometimes sam
 
GK1918 said:
So I dialed in the 4jaw, dialed in the tailstock end to the follow rest and ran one of those swivel knurlers
right in there against the work to the follow rest.
Click to expand...

Sam - that's a great idea, using a knurling tool as an alignment tool. Thanks!

MTBob
 
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