Starrett 68128 Mechanical Inside Micrometer 0.25 in

Product Description

The STARRETT 68128 is a mechanical inside micrometer designed for precise internal bore and hole measurements. It features a ratchet stop thimble that delivers consistent, repeatable gauging force, and self-centering contacts that guide the tool to a true reading without manual alignment. Graduation is 0.0001 inches with an accuracy of 0.0001 inches, making it well suited for close-tolerance work. The measuring faces are solid carbide for durability and wear resistance. This tool is intended for machinists, tool and die makers, metrology technicians, and quality control professionals who require reliable internal dimensional verification.

The 68128 is used in shop-floor and inspection environments where accurate inside diameter measurement is required. It covers a 0.25 inch range and includes extension rods up to 6 inches in total length, extending its utility across a range of bore sizes. The 0.75 inch gauge depth allows measurement in relatively shallow bores. Typical applications include checking cylinder bores, bushing IDs, bearing housings, and machined cavities in both production and repair settings.

Key Features

• Ratchet stop thimble provides consistent measuring pressure for repeatable results
• Self-centering contacts guide the tool to true readings without manual centering
• Solid carbide measuring faces resist wear during repeated use
• 0.0001 inch graduation and 0.0001 inch accuracy for close-tolerance inspection
• Maximum extension rod length of 6 inches expands measuring range beyond base capacity
• Includes case, contacts, setting ring, wrenches, and instructions for ready deployment

Compatibility

Designed as a standard mechanical inside micrometer for use wherever internal bore measurement to 0.0001 inch precision is required. Compatible with standard extension rod sets appropriate for inside micrometer systems of this type.

Installation Notes

Inside micrometers are installed and removed by hand — no power tools or mechanical fastening is involved. Before use, zero and verify the instrument against the included setting ring to confirm calibration. Keep measuring faces clean and free of chips or debris, as contamination directly affects reading accuracy. Store in the supplied case to protect the carbide faces and maintain calibration integrity.