[How do I?] How does one mount a large (heavy) cylinder on a lathe?

Bill Kahn

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I am having a blast with my new PM1030V lathe.

I have a puzzle...

It is a 1030. So, I guess I can machine a 10" diameter cylinder 30" long. Or at least approach those numbers.

I have a 4" diameter steel (sort of) cylinder 7" long. Heavy. I want to make a better cylinder from this stock. How hard could it be? Chuck it up and make sharf.

Well, my chuck with the outside jaws (the ones that grab by pushing out) can only grab a 3" cylinder on their inside. OK, switch over to the inside jaws. They can grab the 4" but less than a half inch of one end. (Remember, this stock is heavy--almost wanted to get out the shop crane to position it.). But, grabbing 1/2 ", even through everything is steel, and really tightening up the jaws--well it is crooked. Steady rest is too small to go around it. Follow rest doesn't support from the bottom. Tried to use the dead center on the tail stock.

OK, now the question--what sequence of adjustments does one do to get the mostly but only sort-of cylinder chucked up basically axially symmetric and ready to turn? I guessed at the center of the cylinder (the end has about 1/4" of gentle wave in it) for the dead center. Got a dimple there. Loosened chuck. Retightened. Clearly I was off of center. But wrongly located dimple was already there.

4-jaw chuck same problem. Face plate--ok, but how do you mount a 7" cylinder to it?

Any suggestions for a big heavy chunk of roundish steel like this?

-Bill
 
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You can very likely fit a larger chuck on your lathe. It might be harder finding a larger steady rest that fits, but you could mock one up out of a tree fork and a saw. I'm only half kidding. You can make a wooden V block that fits your lathe ways, and then and knock it over and shim it up until your indicated in pretty good. Tighten your lathe chuck, Drill your center whole, remove your v-block, and support your part for turning with your center. You may still get a little hour glassing in the middle. I don't really know how much it will sag under its own weight. A good place for precision shims is... Harbor Freight. I periodically stop by and buy half dozen packs of cheap feeler gages.
 
so with the jaws grabbing from the outside you will need the tailstock.
So create a plug to fit into the tailstock end of the tube.
What you want to do is first machine a plug that looks like a hat.
Fit it nicely into the tube end. then create a lip to stop it from pushing in.
Reverse it, then face and center drill the lipped (brim) side.
Put it in the tube use your center to hold the tube in. you can now do any turning you need to the outside. The inside cannot be cut w/out a steady rest.
 
I think he has a solid cylinder. A tube would be easier if only because its lighter.
 
I hate to say it but soft jaws, one may hold diameters far larger then the chuck, a 4 jaw will as well. The limit is that the chuck jaws will hit the ways before the part when holding on the outside.
This is a 20" disk held in a 20" 4 jaw where the jaws just clear the ways.


Good Luck
 
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With a 10x30 lathe, you cannot machine something that is remotely close to 10" dia x 30" long. First of all the cross slide gets in the way, that takes you down to about 7" diameter. The 30" is the absolute max length between center points (no chuck, no ball bearing center), in practical terms you are down to about 24" working length.

You should have no trouble working a piece of 4" diameter bar 7" long. That is a robust piece of material, but strictly speaking, it is nothing special. You will absolutely need tailstock support. You need to get a center drill into the one end - but don't try that in the lathe. There is nothing wrong with just carefully laying out the center (measuring tools) and drill the center with a drill press - even by hand held drill. Of course, do as good a job as you can, but it does not need to be perfect. With a big hammer / center punch - you can migrate that mark you have until it is pretty close.

What chuck? It doesn't really matter. A half inch of grab is plenty (when the outer end is supported). Select a chuck and jaw combination so that the jaws are not sticking out past the body of the chuck (or if they must then as little stick out as possible - this is a safety issue and obviously stronger if they don't stick out).

Keep your speed down: 4" diameter - 100 rpm gives you 100 feet per minute, which for HSS cutting steel is about as fast as you ought to go.

Let us know how you make out. Regards, David
 
I hate to say it but soft jaws, one may hold diameters far larger then the chuck, a 4 jaw will as well. The limit is that the chuck jaws will hit the ways before the part when holding on the outside.
This is a 20" disk held in a 20" 4 jaw where the jaws just clear the ways.


Good Luck
Wreck... What is the red thing in the picture? BW
 
Helps keep the coolant in the machine, a 20" jawed chuck will fling coolant everywhere even at 250 Rpm's.
This is one of the advantages of a collet chuck, no jaws to turn it into a fan (-:
 
The problem you have is the reason when I'm asked . I say get the biggest lathe you can fit and afford. Small lathe equals small work. A lot can be done on your lathe the possibilities are as good as you are. But trying to build cannon barrels on a lathe made for 45-70 barrel. And that would be pushing it. Run your lathe build some projects and tools have fun learning from your lathe. Good luck with all the future builds. Just share is what we like. Pictures and more. Ck marks builds on here if you want inspiration his LATHES a 9" .
 
Here's a crazy idea. How about turning a short bushing that will fit over the shaft and have 4 adjusting screws like a spider to center it up. The bushing is closed on the chuck end and at a diameter that'll fit in your chuck. I'm thinking something like a standard die holder for the tail stock pictured below. Of course, the disadvantage is you can't get to the area in the bushing. Plus it'll eat up some distance between your head stock and tail stock.

Bruce

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