Lathe Levelling - how level?

May seem a daft question, but how much discrepancy in levelling the bed is too much?

I'm aware it's bed twist that really matters, rather than end-to-end or exact side-to-side levelling, but how much twist?

I've found that my grandad's WW1 clinometer (used for setting up the sights on Vickers .303 machine guns - he was the final inspector in one of the factories!) is accurate to 1 minute of angle , which I think is an inch in about 95 yards, and can be set +/- 15 degrees consistently- accurate enough, too accurate?

Thanks all,

Dave H.

Reply to
Dave H.
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Try it. The real test is if it can turn a cylinder parallel to the accuracy you need (or can measure). Uneven wear and misadjustment may cause more error than the twist.

The bubble on my 12" South Bend Lathe level moves about 1/32" per thousandth.

jsw

Reply to
Jim Wilkins

A master precision level is accurate to about .0001" per foot, not exactly sure what that converts to in arc seconds. I use an electronic level that is good to a couple arc seconds, and it is more sensitive than I actually need.

Jon

Reply to
Jon Elson

I make that master level accurate to about 1.7 arc seconds... and a minute of angle is about 3 thou"/foot so a couple of orders of magnitude away :)

Dunno if anyone can give a *quantative* answer though? Currently the Big Toy isn't in working order (still have to hook up the VFD and interface to the original switchgear and 3-speed motor) so I can't do a parallel-turning test, but it appears to be level to less than 20 m.o.a. across the boring table, about 1+1/4 degrees head-down due to a sloping shed floor, and (possibly thanks to the 2 tons of Old Iron) less than 10 m.o.a. of twist?

Cheers, thanks for the info,

Dave H.

Reply to
Dave H.

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