[irnsrgn]

Lathe leveling was brought up at one of the conventions I used to attend and developed into a very heated discussion as usual especially with 80 to 100 shopmen assembled in one room. The part that stuck in my mind was from an 80+ year old Master Machinist who was setting next to me and kept quiet thru it all. But, he did confide in me his tried and true method for setting a lathe as he called it. His method was to shim the headstock end higher than needed and level to within .0001 per foot, then go to the tail stock end and using a little screw jack in the exact middle under the ways to jack it up till the bed was level to within .001 of its length, let it set for 2 to 3 days so the metal in the lathe bed returned to normal as it was machined, check it for level again then check the tailstock end crosswise to the same specs as the head stock. If it didn't level itself in this 3 point contact set up with no external twist to the end, it would never cut true no mater what you did to it.

Most old machinists were very particular and one of the things they always did when turning between centers was to dial in or center the tailstock in the position it was going to be used in every time for each set up.

As for leveling on a ship, its usually fastened down to the steel deck of a ship which in the way its put together gives a very stable un twisting mounting surface. Not counting chance encounters with torpedoes, bombs and internal below decks fires and explosions.

I had a friend who was a machinist on a Sub Tender and for some unknown reason they put the smithy shop directly above the machine shop, the Smithy had a 500 lb LG hammer in it, and they had to give all the compartments below and adjacent to it at least an hours notification prior to using it. LOL