Brief description

High-precision measuring instrument used to measure very small dimensions with accuracies of hundredths or thousandths of a millimeter.

Use / Function

• Precision Mechanics: Measuring shafts, sheet thicknesses, wires, and machined parts.
• Engineering: Quality control in manufacturing.

Operating principle

Based on the micrometer screw: a screw with a very fine and precise thread. Turning the screw advances it a very small, known distance (pitch). Rotation is amplified on a circular scale, allowing fractions of a turn to be read.

How to create it

1. C-Frame: A rigid frame that does not deform.
2. Anvil and Spindle: Flat, parallel contact surfaces.
3. Screw: A fine-pitch screw (e.g., 0.5 mm per turn).
4. Thimble: Graduated cylinder attached to the screw.

Materials needed

• Essential: Hardened steel (to avoid wear on tips and thread), Cast iron (for the frame).
• Tools: High-precision lathe, grinding tools.

Variants and improvements

• Outside Micrometer: For measuring external thicknesses and diameters.
• Inside Micrometer: For measuring hole diameters.
• Depth Micrometer: For measuring groove depth.

Limits and risks

• Clamping Force: Overtightening can deform the part or instrument (a ratchet is used to limit force).
• Temperature: Hand heat can expand the frame; should be held by thermal insulation.
• Cleanliness: Dust on the screw or faces ruins measurement.