Alignment Specs

There are standards for alignment, see "Schlesenger's Universal Tolerances." In Conneley's book on machine tool rebuilding, it is suggested to make a test bar that is hollowed out in steps to reduce sag due to weight, the hole in the end is capped and center drilled to facilitate finish grinding.
 
Here's a link to the 1944 Sheldon Lathe catalog. Page 40 is a copy of the test sheet used at the final inspection just before the machine is sent to the customer:

Note an acceptable spindle runout is .0000 - .0003. Acceptable runout on a free floating test bar 12" from the spindle is .0000 - .0006. The same test sheet appears in several catalogs and brochures as late as 1970. It may have been used longer, but 1970 is the newest catalog I have.
 
According to Schlesinger's book "Testing Machine Tools", the tolerance for the vertical plane and horizontal planes are .0008" in 12", rising in the vertical plane towards the free end of the test bar and in the plane of tool pressure at the free end of the test bar, for lathes up to 15 3/4" center height. For toolroom lathes, these limits are cut in half.
The book was originally published in 1932 and subsequently updated in the late 1930s.
 
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