Precision Level??

[RJSakowski]

I ended up taking a slightly different approach compared to others here. About a year or so ago I was not ready to level my lathe, but I was browsing ebay or something and found what was advertised as a precision spirit level vial (only the vial) for like 7$ and figured it was worth a try. I believe it was supposed to be 2 or 4 arcseconds per division.
I had removed the headstock for cleaning which in hindsight was not very necessary, but I figured I wanted to learn how to align it anyways. Now that I've got the lathe on a sturdy base and reassembled I used the vial to take out bed twist as best I could . I have absolutely no way of verifying it's accuracy but I'd say It's pretty darn sensitive. The lathe stand is bolted to a concrete floor and the difference in reading when I stood next to the lathe as opposed to a metre away was about one division.

It is fairly easy to determine the sensitivity of your level vial. Fix it to a beam and adjust the beam for a level reading. Now place a shim under one end of the beam so that you shift the bubble by one division and using care not to disturb the position of the beam. The sensitivity of the level vial is the thickness of the shim divided by the length of the beam.

A 4 arc-sec./div vial would would have a sensitivity of .00023"/ft and a .0007" shim would move the bubble by one division with a 3 ft. beam..

 

[RJSakowski]

For comparison's sake,

A Starrett 199 master precision level has a sensitivity of .0005"/ft./division or approximately 10 sec./div
A Starrett 98 series level has a sensitivity of .005"/ft./div. or approximately 86 sec./div.
A Starrett 132 series precision bench level has a sensitivity of .080"/ft./div. or 19 min./div.
A typical carpenter's/mason's level has a sensitivity of approximately 1/8"/ft./div. for an 1/8" bubble movement similar movement to the sensitive levels above) or 36 min./ div.
The digital levels like the iGaging Angle Cube read to .05º but the literature states a repeatability of .1º and an accuracy of +/- .2º. Based on my experience with my Angle Cube, I would have to put the repeatability at more like .5º or 30 minutes.
Another option which has been used is a plumb bob. Assuming a length of 3 ft. and the ability to locate the end of the bob to within 1/16" of an inch, this would give a readability of 6 minutes.

Note that the sensitivity specifcations are for a bubble movement of one division or about 1/8". A movement of 1/4th that is easily detectable.

 

[Kroll]

Guys I went cheap on ya'll but others also like this level along with the price.I would have loved to have a Starrett but wife and I want to eat this month so I just could not do both.I believe this level will do just fine and as you can see it was well pack.So off to watch more Youtubes and set it on lathe to see how bad its out.Thanks guys for all the replys and all the suggestions.

 

[WarrenP]

Looks like the same one I have from Grizzly. It's not bad... I think getting it calibrating is a bit strange. Seems like it changes calibration sometimes, unless its me but the starrett I have seems easier to calibrate.