McMaster 94895A029 SAE Grade 8 High-Strength Steel Hex Nut, Pack of 100, Zinc-Yellow-Chromate-Plated, 1/4"-20 Thread TS4000 10 N-m Secondary Scale Minimum

10 N-m Secondary Scale Minimum Torque 115 ft-lb Secondary Scale Maximum Torque 560 ft-lb Extended Data Testing Yes

then Starrett's 572B Thickness Gage is definitely what you need

and the RD700

Ex ia da IIC T4 Ga

McMaster 94895A029 SAE Grade 8 High-Strength Steel Hex Nut, Pack of 100, Zinc-Yellow-Chromate-Plated, 1/4"-20 Thread TS4000 10 N-m Secondary Scale MinimumSAE Grade 8 high strength steel hex nut with zinc yellow chromate plating for corrosion resistance in wet and outdoor environments. Hex Nut Profile Standard Fastener Strength Rating High Material Zinc Yellow Chromate Plated Steel Thread Size 1 4" 20 Width 7 16" Height 7 32" Fastener Strength Grade Class SAE Grade 8 Drive Style External Hex Nut Type Hex Performance High Strength System of Measurement Inch Thread Direction Right Hand Thread Fit Unified