Screw gauge

Vernier caliper

Gear tooth vernier caliper

Feelar gauge

Lock the index crank in position

Eliminate counting holes each time

Fix the index plate on its correct location

Avoid the back lash of worm and Worm wheel

20

28

40

46

Sector arm

Index plate

Worm shaft

Worm gear

Good quality iron tube

Good quality round rod

Good quality copper sheet

Good quality steel sheet