Starrett 68133 Mechanical Inside Micrometer 3/4 in

Product Description

The STARRETT 68133 is a mechanical inside micrometer designed for precision internal bore measurement. It features a ratchet stop thimble for consistent measuring pressure and three self-centering contacts that automatically align to the bore centerline for true, repeatable readings. The measuring faces are solid carbide for long service life in shop environments. With a graduation of 0.0003 inches and an accuracy of 0.000150 inches, this instrument is suited for close-tolerance work where surface finish and fit matter. Licensed machinists, tool-and-die makers, and precision maintenance technicians are the primary users.

The 68133 covers a measurement range from 16.00 mm (minimum) to 0.7500 inches (maximum), making it appropriate for small bore applications in precision manufacturing, maintenance, and inspection work. The gage depth of 2.4375 inches allows measurement inside bores with adequate clearance, and the maximum extension rod length of 6.0000 inches expands reach when needed. This instrument ships complete with a case, contacts, setting ring, wrenches, and instructions, allowing the technician to verify and use the tool immediately upon receipt.

Key Features

• Solid carbide measuring faces resist wear for sustained accuracy in production environments
• Ratchet stop thimble delivers consistent contact pressure, reducing operator-to-operator variation
• Three self-centering contacts locate automatically on bore centerline for true diameter readings
• 0.0003 inch graduation with 0.000150 inch accuracy supports close-tolerance inspection work
• Maximum extension rod length of 6.0000 inches expands measurement reach beyond the base range
• Includes case, contacts, setting ring, wrenches, and instructions for immediate use

Compatibility

Designed as a general-purpose mechanical inside micrometer suitable for small-bore measurement applications in precision machining, maintenance, and quality inspection environments.

Installation Notes

Inside micrometers are calibrated and used by machinists, tool-and-die makers, and precision maintenance technicians. Before taking measurements, verify the instrument against the included setting ring and allow the tool and workpiece to reach the same ambient temperature to minimize thermal expansion error. Clean the bore and measuring contacts before use. Store the instrument in its case when not in use to protect the carbide faces and maintain calibration.