Accuracy: ?2″.
To inspect protractor, taper gage, index plate, index head and goniometer, can also be used to set angle.
Made of special alloy steel, hardness HRC64, high stability, wear resistance and easy combination.
Can be combined to any angle with interval 6 seconds after combination (6″, 12″, 18″, … , 360?).

Standard Abrasives 709187, A/O Straight Cartridge Roll, 1/2 in x 1-1/2 in x 1/8 in 60, 7100085869
3M 07054, Scotch Printable Flatback Paper Tape 256, White, 1 in x 60 yd, 6.7 mil,36 per case (12 rolls/pack 3 packs/case), 7010378934
3M 77579, Cubitron ll Cloth Belt 784F, 36+ YF-weight, 1/2 in x 24 in, Fabri-lok 45 Angle, Single-flex, 7100232690, 200 per case 
