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Machining large cylinders

I ran centerless grinders in production for over twelve years before changing careers. We had all the books from Cincinnati and you would be amazed at some of the rigs and fixtures they showed for infeed and throughfeed grinding. With a little imagination, this would be quite doable.
I had several years on Cinci centerless grinders as well and we did have all the books also. The ball bearing grinding shown in the book always tickled me. Maybe possible but I certainly won’t be involved. We ran some 3 1/2” a few times a year and that sucked.
 
I ground the OD of 18 inch diameter fiberglass pipe in a cincinnati centerless. A larger machine will do the job very well.
 
That is a lot to ask without grinding.

That wouldn’t be a problem for any shop doing shaft work in the Fox Valley of Wisconsin. Paper rolls demand tighter tolerances. They would quote grinding 100% of the time.

Your mid shaft runout might be the shaft pulling away from your center as you are at max bending moment in the middle. There are many other variables hard to diagnose.

I thought I knew how to run a lathe until I worked in the Fox valley with the paper roll lathe hands. Making hollow paper rolls with a few tenths runout became easy.
 
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Making hollow paper rolls with a few tenths runout became easy.

So, what's the secret? How did you hold the rolls: chuck and center, chuck and chuck, chuck and steady, chuck and 2 steadies, something else? Anything special around balancing before turning?

Or were you doing that roll work on a dedicated roll grinding machine like with dual hydrostatic steadies?
 
What'd that do do your coolant?
You nailed it. The grinding removed a lot of material and the settling tubs had to be emptied 4-5 times per day. Back then they had us just fork lift them outside and dump them in the corner of the lot. A few years after that job I heard they had a big EPA fine and needed a lot of remediation.
 
So, what's the secret? How did you hold the rolls: chuck and center, chuck and chuck, chuck and steady, chuck and 2 steadies, something else? Anything special around balancing before turning?

Or were you doing that roll work on a dedicated roll grinding machine like with dual hydrostatic steadies?
From a turning perspective, keep the stresses out and do not fight the natural straightness of the roll. We used what ever chuck was on the machine, either a 4 jaw or a 3 jaw adjust tru with bronze pads so you are just hanging on by a bit and a good center. Sometimes we would stabilize a roll with just the bottom two rolls of a steady to add a dampening point. If you slide the work back into the chuck you will be be bending the roll as you turn it. One thing that is important is to recut your centers to keep them in the middle. We would support the roll in a steady and recut the centers before semi finishing. The drive ends would tweak after they were shrunk into the roll itself. The grinder hands asked for runout less than a thou when we gave them a roll.
The goal is to keep the inside or the tube concentric with the OD, less balancing is required. We did not grind large enough rolls where they wouldn't fit in our universal grinder. There is a shop in the Valley that has Farrel roll grinders that locate and spin the roll off the bearing journals.
 
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Thanks for the tips @MCritchley ! There's a lot of invaluable experience summed up in what you wrote.


Sometimes we would stabilize a roll with just the bottom two rolls of a steady to add a dampening point.

How does this add dampening? Is there a special 3rd point of contact on the steady to absorb vibrations, or is it more about not gronking down on the work from all directions?


We used what ever chuck was on the machine, either a 4 jaw or a 3 jaw adjust tru with bronze pads so you are just hanging on by a bit and a good center.

I see, so truly turning between centers with just enough chuck grip to drive the work.

Did you ever have the bowing problem that @gregormarwick brought up? How'd you solve it if you did?

One thing that is important is to recut your centers to keep them in the middle.

If all the turning is between centers, how do the centers in the work get out of concentric with the OD? Are we talking a dead center on the tailstock end that would wear the initial center cut in the work?
 
Thanks for the tips @MCritchley ! There's a lot of invaluable experience summed up in what you wrote.




How does this add dampening?

It doesn’t, it prevents sag. The roll is not over-constrained in this case.

I see, so truly turning between centers with just enough chuck grip to drive the work.

No, not turning between centres.

If all the turning is between centers, how do the centers in the work get out of concentric with the OD? Are we talking a dead center on the tailstock end that would wear the initial center cut in the work?

Referring to when the centre is installed in the spindle. Whenever it’s replaced, skim cut to true it up and you’ll be dead-nuts every time.
 








 
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