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

[benmychree]

To support the outer end of the tube, make a "spider", a disc of steel with 3 or 4 radial holes on it's periphery, tapped for square head setscrews, perhaps 3/8 NC, the disc will have a center hole facing the tailstock in its center, a pipe coupling of a size that its pipe size will fit through your spindle will be welded in the center of the backside and a piece of pipe screwed in; a cross hole is drilled through the pipe to locate the spider axially with regard to its necessary location inside the end of the workpiece. P pin is made to fit the crosshole, and it will bear against the end of the spindle, so the spider will not slide back into the tube against the pressure of the tailstock center. The setscrews are used to center the outer end of the workpiece similar to chuck jaws and allow safe facing and turning cuts or shallow boring cuts in the very end of the workpiece. If a shallow counterbore is made in the end of the tube in this manner, a steel disc can be inserted into the counterbore (fit tightly) so that when the part is turned around for boring from the other end, the chucking pressure will not distort the tube, and also it plugs that back end so that coolant is not thrown all over the place by the chuck jaws,
This method is especially good for making thin bushings from stock having enough length to allow the wastage of the counterbored part to machine off after the part is finished.
So far as the 7" length of the part is concerned, it will be necessary to cobble up some sort of steady rest. I have made them from steel plate machine burnt and machined up like a normal looking item, I have also made wooden patterns and had the cast in iron, which is the proper way to go about it. For smaller lathes it may not be necessary to make the rest hinged as most are; I just made one for my 9" Monarch lathe from the WW-1 era, A friend had an original, so I just copied it; it was made solid, no hinge, but with the front section open where the normal fastening point would be. For a small lathe it is not so important to have the hinge feature, and it is lots simpler to make.

 

[benmychree]

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

View attachment 241446

Technically what you describe is not a spider, but a "cat head" or maybe derived from "cap head". Using a spider inside makes the job much easier as several operations may be done in one setting of the workpiece. Also called a spider is a sleeve that will fit over the workpiece, having two rows of setscrews for centering with enough space between them to allow the steady rest jaws to run between them.
I once machined some very long crane drum shafts that were rough forgings, they were so limber that chatter was a large problem, so a spider of that sort was located about in the middle of the shaft and adjusted to run true and steady rested; no more chatter problem. A cat head can be used on a similar job to center the end of the shaft accurately enough so that a steady rest spot can be turned behind it, steady rested, the cat head removed and the shaft end properly faced and centered. If the workpiece were a piece of cole finished shafting, no problem, but we were working with roughly hammered forgings that could not be steady rested.

 

[12bolts]

Well, my chuck with the outside jaws (the ones that grab by pushing out)

Bill, just as a matter of clarity and future reference, the description of chuck jaws describes the location of the jaws on the work. Outside jaws are outside of the work and operate by pushing inwards.

Cheers Phil

 

[Bill Kahn]

Bill, just as a matter of clarity and future reference, the description of chuck jaws describes the location of the jaws on the work. Outside jaws are outside of the work and operate by pushing inwards.

Cheers Phil

Thank you. So much to learn. How to hold on tight to a 25 lb chunk of steel and also the name what I am suppose to use to do so. All lessons gratefully received.