Spi 21-912-1 Mechanical Hole Micrometer 2.5-3.0 in

Product Description

The SPI 21-912-1 is a mechanical hole micrometer designed for precision internal bore measurement in the 2.5 to 3.0 inch range. It delivers 0.0002 inch graduation and 0.0002 inch accuracy, making it a reliable tool for checking bore diameters to tight tolerances. Three self-centering contact points ensure consistent alignment within the bore, while carbide measuring surfaces resist wear over repeated use. A ratchet stop thimble controls applied measuring force for repeatable readings. The instrument ships calibrated with a NIST traceability certification included, satisfying quality system requirements on the shop floor or in the field.

This hole micrometer is suited for machining, metrology, and maintenance applications where internal bore dimensions must be verified against engineering tolerances. Typical use cases include checking cylinder bores, housing bores, and large-diameter fitted holes in industrial equipment. It is appropriate for use by machinists, quality technicians, and precision maintenance trades working in manufacturing, heavy equipment service, and toolroom environments. The included 2.5 inch setting ring allows the instrument to be set to a known reference before measurement.

Key Features

• Measurement range: 2.5 to 3.0 inches with 0.0002 inch graduation
• Accuracy: 0.0002 inches across the full measurement range
• Three self-centering contact points for consistent bore alignment
• Carbide measuring surfaces for extended service life
• Ratchet stop thimble provides controlled, repeatable measuring force
• Ships calibrated with NIST traceability certification included
• Includes one extension rod and one 2.5 inch setting ring

Compatibility

Designed as a general-purpose mechanical hole micrometer for internal bore measurement applications in the 2.5 to 3.0 inch range. Suitable for use wherever a calibrated inside micrometer with NIST traceable certification is required.

Installation Notes

This instrument is a precision measuring tool, not a component that is installed in a system. Handle with care to avoid dropping or striking the measuring anvils or thimble. Store in the provided case when not in use to protect the chrome finish and carbide contact points. Zero the micrometer against the included setting ring before each measurement session to confirm calibration status.