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Repair "pineapple" roller shaft.

Overland

Stainless
Joined
Nov 19, 2017
Location
Greenville, SC
A guy brought me this shaft to repair, 40" long, 4" OD - the end was damaged and also bent. He had started to repair by welding up the shaft, then trying to turn it, but he didn't have a steady rest - ??????
So I set it up and had quite a time getting it true in the steady - the shaft was bent about 1/8" off my estimated center. I used a level on top, and a dial indicator with a 6" rule to give me a flat surface. I welded up the rest of the shaft and started to clean it up. My thinking was once I got a clean diameter, I could measure any taper, then take it out by adjusting the steady to get it running parallel.
So I was out by 0.003" on the 8" length of the shaft - that'll do.
A buddy said later that I could have turned a piece of scrap to the "good" diameter on the job, and set the steady up on that - good idea.
Any other suggestions how this steady could be set-up true ?
Bob
Edit: The pic shows the job as he brought it to me; he had tried to turn it between centers, then realized shaft was bent.
 

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When I use a steady on a finished part that I do not want to show wear marks, I wrap a piece of steel shim stock around the part and hold it in place with a worm hose clamp near the steady fingers. The shim is trimmed so there is no overlap of the ends, just a very small gap. This plan would also work on a knurled shaft, but with thicker shim stock than what I would normally use.

In this sort of case, I clamp the end of the part in the three-jaw so that the far end of the part has minimal wobble. Then I set the steady fingers on the part with the steady as close as possible to the chuck, using the same shim stock and clamp. Then I move the steady toward the tailstock and reposition the shim and clamp and close the steady on the part.

Larry
 
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Chuck the roller up and support the free end using a pad with a center hole in it and the tailstock center. Apply enough tailstock pressure the free end is supported. Indicate the steady rest journal and tap it around until it runs true. Bring the steady rest pads up until they just touch.
 
I generally use the turned scrap to set the steady but depending on the wear of the ways when you move out to the end there may be some shift so using Guy's method takes care of that. Just depends on how heavy and long the roller is.
Once centered I recut the center with a single point tool .
 
Chuck the roller up and support the free end using a pad with a center hole in it and the tailstock center. Apply enough tailstock pressure the free end is supported. Indicate the steady rest journal and tap it around until it runs true. Bring the steady rest pads up until they just touch.

In this case the end of the shaft needing repair was bent about 1/8" out of line, so I couldn't use a tailstock center.
Also to indicate on a true diameter it would need to be held only in the chuck. In this case the shaft is 40" long 4" bar, that weighs about 100 lbs. I had no confidence in hanging that out of the chuck.
My crude method actually worked out quite well. But I do like the idea of turning a slug the right size, setting the steady on that, then repositioning the steady.
As pointed out, the risk is wear in the bed may screw things up, but if you measure any taper you might have, before the finishing pass, then the steady can be adjusted to take it out.
Thanks for comments.
Bob
edit: I welded up the old center hole and drilled new one.
 
In this case the end of the shaft needing repair was bent about 1/8" out of line, so I couldn't use a tailstock center.
You can still use the tailstock center. The pad you make becomes a faux center. It has a center hole that fits on the center and is flat on the other face. Jam the flat face against the end of the roller and friction will support the 50# of that end. So you are not using the bent center in the shaft. Indicate the spot you are gonna put the steady rest on and tap the end of the roller adjacent to the pad until the steady rest journal runs true. The bent part will be running out however much it is bent at this point. Adjust the steady rest, back the tailstock off, and recut the center true.

This works great and eliminates pricking around setting the steady rest by the chuck and moving it, or worse simply guessing. I've seen guys struggle setting the steady rest only to have it so far eccentric with the rotational axis the part wiggles out of the chuck. Kinda scary!

The limiting factor is the weight of the shaft. The pad friction has to support that weight.
 
On similar parts I weld up the center hole and straighten as necessary. Then I put it on the horizontal boring mill and put in a new center, and turn between centers. Before the boring mill I would hang it off the back of a B'port table and swivel the head over.
 
I welded up the old center hole and faced it off.
I put a large center drill in the tailstock. I figured the alignment was pretty good "up & down", not so good side to side. So I orientated the center drill with the point line up and down. I fed the drill slowly and the center drill marked a small circle about 1/8" diameter.
Really easy then to adjust the steady to get the center drill point in the middle of the circle; then when I started to drill the new center I was getting chips from both flutes !
I figured I nailed it at that point.
Job came out really nice.
Piece of cake.
Bob
 
Cat head.

True a running spot on the shaft.

Set steady rest.

Drill or cut a new center.

Install live center in tailstock.

Move or remove, steady rest.

Machine shaft.
 








 
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