Question 1

Why should sine bars not be used above 45°?

Accepted Answer

Above 45°, the sensitivity dθ/dH = 1/(L×cos θ) increases rapidly. At 60°, a 0.01 mm stack height error produces 0.0057° angle error, while at 30° the same error produces only 0.0033°. At 80°, sensitivity is 3× higher than at 0°. For angles above 45°, set the complement angle (e.g., for 70°, set 20° and orient the part accordingly) or use a sine table with angular readout.

Question 2

How do I build the optimal gauge block stack?

Accepted Answer

Use the successive subtraction method: start with the target height, select the block that eliminates the last decimal place, subtract and repeat. For 27.385 mm: select 1.005 (→26.38), then 1.38 (→25.0), then 25.0 mm. Total: 3 blocks. Minimize the number of blocks (each wrung joint adds ~0.25 μm uncertainty). Maximum recommended stack is 5-6 blocks.