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Old 10-20-2021, 06:37 PM
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Default What's wrong with my setup?

Material is 2" 1018 cold rolled steel.

Need to machine a part out of it for the ironworker in another thread.

Turn down the od, bore and thread id and part off to length.

Chuck is as tight as I can physically get it but it keeps spinning out of the chuck jaws. It's also fully seated into the chuck.

Used this chuck before and didn't have this issue.
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Old 10-20-2021, 07:09 PM
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How did you set up the steady rest?
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Old 10-20-2021, 07:33 PM
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Use a 4 jaw and indicate the shaft then put the steady on
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Old 10-20-2021, 07:44 PM
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if you have not got the steady rest lined up properly it will walk out.
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Old 10-20-2021, 07:46 PM
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I would do it on centers if you can. It also looks like there is way too much load on the bearings on the steady rest. Possibly the bar is bent or out of round
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Old 10-20-2021, 07:53 PM
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Quote:
Originally Posted by milomilo View Post
How did you set up the steady rest?
Check this,

Do you have a dial indicator? If so check the end of the shaft and see if it is wobbly. this indicates it is not positioned correctly in the steady rest. ( gee I wonder How I would even know to suggest this)

Also make sure the bearings are all free in the steady rest.

Scott
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  #7  
Old 10-20-2021, 08:26 PM
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Put the bar in the chuck, slide it in till there's only a couple inches sticking out then face it off and drill a centre hole. Once you've drilled it, slide it out as far as you need it and run the tailstock centre in to support the outboard end. Once you've done that machine a narrow strip where you want the steady to run, then set up the steady so it's just snug where it's running on the shaft. If at all possible try to use the live centre for as much of the process as you can and it's generally a good idea to run a bit slower RPM if you can get away with it.

When using a steady the area where you run it needs to be round and concentric to the centreline of the workpiece. This applies to any steady rest but it's especially important if you're running a roller bearing steady. I have found the latter to be quite unforgiving when it comes to alignment of the workpiece. I would try and find a steady that uses brass or bronze for the bearing surface.

I'm pretty sure this will fix your problem; if it doesn't then you've got some misalignment somewhere. Those rollers only need to be cocked a little bit to suck the material out of the jaws...
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Old 10-20-2021, 08:51 PM
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I did check run out at the steady rest and I've only got .002".

I did not check at the chuck but I know that three jaw chuck has about .030" run out.

I think I should put the 4 jaw back on.
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  #9  
Old 10-20-2021, 09:10 PM
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Kieth has good advice.


Couple questions I have, How big is through hoke in your lathe. I’m assuming not big enough to put entire bar in, so you only have a little bit stickout from the chuck.

If you can’t stick it thru far enough so you only have like a inch sticking out in order to face off and center drill the end, then try the following.

Stick the bar as far in the chuck as you can. Do not tighten the steady rest in yet. Use a dial indicator to see how far bar is running out at the chuck. Use a dead blow hammer, or a piece of aluminum or brass to hit the jaws/ bar as needed to try to get as much runout out as possible. Then at this point start tightening one off the lower steady rest rollers in. When the roller starts to turn, adjust the opposite lower roller. Keep alternating between all three roller then, until you can just feel a bit of slip on each roller. If you hold your finger against the roller, you will feel it stop slightly, and then grab again. Careful not to pinch your finger in roller.

At this point, you should be able to face the end, and center drill the end for the tail stock center. After this, hold the end with the tailstock center, and then true up the rod where you want to run the steady rest. Now you should be able to tighten the rollers up, and they should all roll on a trued up round surface. Keep the rollers as loose as you can, to keep heat buildup down. But you might need to tighten a bit if you get chatter marks while turning.

If you only need a small piece, sometimes it is better to cut a smaller piece, and do away with the steady rest if possible. Just leave a bit of extra material if needed to hold into the chuck, that you can machine off at the end.


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  #10  
Old 10-20-2021, 09:16 PM
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Quote:
Originally Posted by OldRedFord View Post
I did check run out at the steady rest and I've only got .002".

I did not check at the chuck but I know that three jaw chuck has about .030" run out.

I think I should put the 4 jaw back on.

The steady will bend the bar to where ever you have it set to, and hard to get it concentric with the center line of lathe spindle. You would need to run a dial indicator lengthwise along the bar, with the indicator mounted on the carriage, and check for runout. You would need to do this on the to of the bar, and the front side to, 90 degrees from the top. This will tell you if you have the steady holding the bar centered, as long as the bar is straight.

The four jaw might be better for you , if you have that much runout in the three jaw. That really sounds excessive. Are you sure the jaws are in correct order?


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