Machinist level specs seconds vs tenths/10"

[AGCB97]

I'm looking at level specs of various levels.
Starrett gives 0.42 mm/m or 80 to 90 seconds
How does this compare to .0005/10"
My math seems to not work

Thanks
Aaron

 

[T Bredehoft]

0.42 mm/m

equals .0165 per 39.37 inches.

If your Starrett level is 10 inches long, that would equal ,0042 in 10 inches. Someone please check my math.

 

[RJSakowski]

10 seconds of arc equals approximately .0005"/10" or .0006"/12". A second of arc is 1/3600 degrees. The sine of 1 second of arc is 4.848 x 10^-6 (.000004848) That times 10" is .00004848". For very small angles, the sine, tangent, and arc in radians (2π radians equals 360º) are close to equal so 10 seconds of arc = .00048"/10".

 

[mikey]

Per Starrett, Main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42mm per meter)

 

[AGCB97]

Per Starrett, Main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42mm per meter)

Should that be .0005" per foot?

 

[RJSakowski]

Should that be .0005" per foot?

Starrett' 98 Series levels are .005"/ft. Their 199 series level is .0005"/ft.

 

[woodchucker]

equals .0165 per 39.37 inches.

If your Starrett level is 10 inches long, that would equal ,0042 in 10 inches. Someone please check my math.

That's correct.

 

[benmychree]

Starrett' 98 Series levels are .005"/ft. Their 199 series level is .0005"/ft.

The bottom line is that the 98 series is not good enough to precision level a machine tool such as a lathe, but is adequate to level such as milling machines, drilling machines, etc.

 

[Optic Eyes]

The bottom line is that the 98 series is not good enough to precision level a machine tool such as a lathe, but is adequate to level such as milling machines, drilling machines, etc.

Thats good enough for checking for twist i a lathe bed as well as levelimg, let it sit in use and see if it holds tolerances or check with a 199 Starrett or a King gage.

 

[benmychree]

I quite disagree with the above statement, a Starrett #98 is nowhere near sensitive for lathe alignment, it is only good enough for rough leveling in preperation with a .0005 resolution (or better) level for final alignment.