# Machinist level specs   seconds vs tenths/10"



## AGCB97 (Jun 24, 2017)

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


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## T Bredehoft (Jun 24, 2017)

AGCB97 said:


> 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.


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## RJSakowski (Jun 24, 2017)

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".


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## mikey (Jun 24, 2017)

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


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## AGCB97 (Jun 24, 2017)

mikey said:


> 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?


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## RJSakowski (Jun 24, 2017)

AGCB97 said:


> Should that be .0005" per foot?


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


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## woodchucker (Jun 24, 2017)

T Bredehoft said:


> 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.


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## benmychree (Jun 24, 2017)

RJSakowski said:


> 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.


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## Optic Eyes (Apr 10, 2021)

benmychree said:


> 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.


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## benmychree (Apr 10, 2021)

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.


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## Optic Eyes (Apr 11, 2021)

benmychree said:


> 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.


I have been a Millwright installing Machinery in industry, and a machine rebuilder since 1969, I worked in Nuclear power plants installing Turbines and Reactors, I did precision alignment on paper mil!s, web lines, extruders, Screw machines and Tool room equipment including Moore Jig bores and grinders, I rebuilt Harding's lathes, tool room, chuckers, and Harding's CNC, My own Company produced Precision squares and straight edges.  So what your extensive experience BTW?


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## benmychree (Apr 11, 2021)

I started my machinist apprenticeship in 1964, worked in that shop for seven years running things up to 5" bar G&L boring mills 87" swing lathe, universal cyl. grinder 16X72 big surface grinder,  vertical boring mills, all common machine tools, then worked for a refrigeration shop doing industrial refrig (ammonia ) work and machine work, then started my own machine shop with over 4,000 sq ft of space full of standard machine tools, much like the machinery that I trained on until I retired about 10 years ago, at home I have some of the same machines, as listed below.  I also have done considerable scraping and rebuilding and considerable wood patternmaking for my own and other's projects, including making replacement parts for the winches on a steam donkey at a steam sawmill that I volunteer at, where I mostly run the engines that power it; Google "Sturgeon's Mill" and see pictures and videos.  In my shop we did repair work and made a line of products to serve the wine industry.  The shop I apprenticed was Kaiser Steel in Napa Cal. it is all gone now but was a large fabricating operation that built small ships during WW2, and later a bunch of barges, bridges, cranes for their steel mill, pipe mill machinery for large diameter oil and gas transmission, built pipe mills for UK, Germany Japan, and others and did all the framing for the Transamerica building in San Francisco.  A pipe mill for up to 48" diameter 15/16" wall welded steel pipe 40 feet lengths was also part of the operation, as was a mill to make steel tunnel liner segments for the BART rapid transit in the SF Bay area.
As you know precise alignment is quite important especially in large machine tools, the G&L boring mills needed to be leveled quite closely, these had  feet of vertical travel I had to relevel one that spent a lot of time on, and used a .0005 level to do it, to perhaps only one graduation or less, it is surprising how flexible such big machines can be and how little pressure on a wrench can send the bubble scooting along.


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## Optic Eyes (Apr 11, 2021)

Good resume nice to neet you, I worked on Giddings & Lewis boring mills, repairing them. I pushed a job moving a big machine shop that omly did BIG work, their Horizontal bar was twenty feet tall table big enough to park cars on, on big stuff like that I shoot it in with K& E Jig transits and Tilting levels, like when we aligned steam turbines at Power Houses, I started when tight wire alignment was used but Optics took over, I taught optics as well. 
My comment was sometimes to sensitive can work against you if you cannot correct it, but I always let machines go to production then relevel, there is a lot of bad castings used today.


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## benmychree (Apr 11, 2021)

Optic Eyes said:


> Good resume nice to neet you, I worked on Giddings & Lewis boring mills, repairing them. I pushed a job moving a big machine shop that omly did BIG work, their Horizontal bar was twenty feet tall table big enough to park cars on, on big stuff like that I shoot it in with K& E Jig transits and Tilting levels, like when we aligned steam turbines at Power Houses, I started when tight wire alignment was used but Optics took over, I taught optics as well.
> My comment was sometimes to sensitive can work against you if you cannot correct it, but I always let machines go to production then relevel, there is a lot of bad castings used today.


I liked working at that shop for the most part, but I got laid off and needed to find another job when my unemployment was about to run out, and would have gone back when work got going again, but there was a boss there who had been their first apprentice and was the night superintendent's son in law, he was a dumb F*** and he and I did not get along, so I did not see a future there; so I declined to return, the irony was that within a year of me not going back, he was divorced and subsequently fired twice and died of alcohol related causes.  I kept in contact with the shop and visited old friends there regularly, and ended up buying several machines and equipment when the closed the doors.  They had three of those 350T G&Ls, one fairly new, sold for only 30K about 15 years ago, with all tooling.  Good to meet you too, look forward to reading your comments in the future.  Another thing they had in that facility was an Ingersoll floor mill with 13 ft up and down and 44 ft of horizontal with head and column swivel, all DC electricals --- actually they had two of them, one with only 20 ft of travel, and yes, you could park cars on the tables, which were flush with the shop floor.  Later under a different management they bought and used a lathe with 16 ft swing and 100 ft between centers with two carriages for a seismic retrofit job on the SF-Oakland bay bridge, a "pin" assembly about 5 ft in diameter and about 40 ft long.


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## Optic Eyes (Apr 11, 2021)

Really big stuff is fun, working in the power plants we ground the tips of the turbine blades, the lathe was a headstock and tailstock of big blocks bolted together
the 100 ton rotor was on centers with a driving plate and big lathe dog, there was a big wood scaffold like a bleacher in a stadium, we had a rail to clamp a tool post grinder to grind the blade ends. Bolts on a turbine can be 5" in diameter and as many feet long
I wanted to work at Westinghouse where they made that stuff.


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## benmychree (Apr 11, 2021)

Sounds like good fun; I detest tiny workpieces; fingers too big!


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