how to level south bend 9

[dansawyer]

The lathe is a a late 1945 South Bend 9a. It has an under motor mount. After much back and forth the lathe is installed on a new table. It is a tool room model with a free floating foot. In other words the bed is supported by 4 bolts to the casting near the head and the foot is supported by a floating cylinder that allows rotation about the bed longitudinal axis.
I purchased a master machinist level. It is accurate to .0002 inch per 10 inches. I have no practical way to test this the limits but I have been able to confirm is at least in the range of 10ths. I used the level on the saddle to test the saddle run out across the travel. It was actually very good for this a lathe this old, about 1 1/2 thousands end to end.
However I am unable to verify the horizontal flatness. The tail stock V is higher then the saddle V's. Simply setting the level on the saddle is a close approximation. Is this good enough? Is there a straight forward way to level this dimension? Given the nature of the three point support it should only be necessary to level this axis at the head. I there a good place to do this.
BTW: If anyone is interested this is a very interesting process. The level measurements respond to the weight of the saddle as it is moved end to end. There is some inherent flex in the mounting. I have not determined what is attributable to the bed versus the table.

 

[benmychree]

A machine with 3 point fastening down to the bench should not need to be leveled, it should be inherently in alignment wherever it sits; on such a machine level makes no difference, alignment it where its at. A lathe with a 4 point perch also needs to be in alignment, and transverse leveling is usually all that is required, and is one way to assure alignment, on a machine with little wear, alignment can be had by simply cutting two bands on a test bar about 6" apart and shimming one of the machine legs until it cuts straight, a level not being strictly necessary, a lathe with 6 or more legs would be difficult to achieve alignment without leveling, due to sag in the area of the center legs, so it would be leveled both transversely and axially.

 

[mikey]

However I am unable to verify the horizontal flatness. The tail stock V is higher then the saddle V's. Simply setting the level on the saddle is a close approximation. Is this good enough?

Yes, just make sure the cross slide bed is free of protruding nicks or dings and set the level on the cross slide. Check level at both ends of the bed and adjust until they're the same. Then do a 2-collar test to verify and fine tune.

 

[Technical Ted]

There's a small section in here on bench lathes. I thought it might be some good general leveling and testing information to help you.

Ted