FYI: Starrett Accuracy Specs (Squares, Comb Squares, Rules, Straight edges)


Hi,
I've been looking into Squares, Combination Squares, Rules and Straight edges. Trying to determine price versus performance trade offs. I just got an email from Starrett with a their technical specs in a few MS Word documents so I thought I'd post some info as people see interested about this stuff. [prices are from ww.msc-direct]
SQUARES
Part No 13             Squareness:    .0015" 14             Squareness .0005" 20             Squareness:    .0001" per foot 21    Outside and Inside Squareness .002" 55             Squareness:    .0001" per foot 61             Squareness:     .0005" 453             Squareness:     .0001" 457             Squareness:     .004" per inch
COMBINATION SQUARES
Square Heads - Squareness of head to blade (90 degrees) 2 1/2" (+/- .0005") 4", 6" (+/- .001") 12" (+/- .002") 18" (+/- .003") 24" (+/- .004") 150mm (+/- .02mm) 300mm (+/- .05mm) 600mm (+/- .1mm) Lateral squareness - 1/2 width of blade maximum. Miter (45 degrees) - +/- .004" per foot (12")
Center Heads - Working edge shall bisect 90 degree angle within +/- .005" (+/- 3 minutes)
Protractor Heads - Base to blade inspection within .004" 90 and 180 degree inspection within (15 minutes) Base concavity tolerance .002" maximum
RULES AND COMBINATION SQUARE BLADES
Scale Accuracy: End grind to the first / last inch line, 1" (+/-.0025")

first 6" (+.004"/-.0035") 6"-12" (+.005"/-.0035") 12"-18" (+.006"/-.0035") 18"-36" (+.007"/-.0035") 36"-48" (+.010"/-.0035") 48"-60" (+.011"/-.0060") 60"-72" (+.012"/-.0070") 72"-96" (+.014"/-.0090") 96"-120" (+.016"/-.0110") 120"-144" (+.018"/-.0130")
Over All Length: 6" +.004"/-.0020" 12" +.005"/-.0035" 18" +.006"/-.0035" 24"-36" +.007"/-.004" 48" +.010"/-.005" 60" +.011"/-.006" 72" +.012"/-.007" 96" +.014"/-.009" 120" +.016"/-.011" 144" +.018"/-.013"
Straightness: .001"/Foot from Mean Plane Parallelism : .002"/24" Squareness : 5 Minutes or .0015"/Inch
STRAIGHT EDGES
Edge straightness:    .0002" per foot from a mean true plane. Total                     variation, from high spot to low spot, can be .0004"                     per foot at any point along its edge. Flatness:    No curvatures perceptible to the naked eye. Parallelism:    within .0004" per foot.
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