For very accurate measurements micrometer calipers are used.

Micrometer Caliper

For very accurate measurements micrometer calipers are used.

For very accurate measurements vernier calipers are used.

Vernier Caliper

For very accurate measurements vernier calipers are used.

Measuring chordal thickness with gear tooth vernier.

Tooth Vernier

Measuring chordal thickness with gear tooth vernier.

Gear tooth vernier.

Tooth Vernier

Gear tooth vernier.