Spi 10-744-1 Mechanical Hole Micrometer 3.2 Inch Range

Product Description

The SPI 10-744-1 is a mechanical hole micrometer designed for precise internal bore measurement. It features a ratchet stop thimble for consistent gauging pressure and solid carbide measuring anvils for long-term durability in production and inspection environments. The instrument delivers a graduation of 0.0002 inches and an accuracy of 0.000250 inches, making it suitable for applications where close-tolerance bore verification is required. Machinists, toolmakers, and quality control technicians use this micrometer for measuring hole diameters in metal, plastic, and composite workpieces.

The SPI 10-744-1 is suited for shop-floor and lab metrology applications requiring accurate internal diameter measurement. The three-contact-point design promotes self-aligning and self-centering behavior inside a bore, reducing operator error during measurement. The micrometer covers a maximum measurement range of 3.2 inches, with a maximum extension rod length of 6.0 inches and a gage depth of 3.54 inches. It is appropriate for use in precision machining, manufacturing quality control, and tool and die work where repeatable bore measurement is critical.

Key Features

• Solid carbide measuring anvils for extended wear resistance
• Ratchet stop thimble provides consistent and repeatable gauging force
• Three-contact-point design is self-aligning and self-centering in bore
• 0.0002 inch graduation with 0.000250 inch accuracy
• Maximum extension rod length of 6.0 inches for deeper bore access
• No digital counter — purely mechanical readout for reliable shop use

Compatibility

Designed as a direct-use hole micrometer for internal bore measurement applications requiring a 3.2 inch maximum range; no setting rings are included with this unit.

Installation Notes

This instrument is handled and used by machinists, toolmakers, or quality control technicians — no power source or wiring is required. Before use, clean the measuring anvils and bore surface to remove debris that could affect readings. Store the micrometer in its case away from heat sources and cutting fluids to preserve calibration. Periodic calibration verification against a certified standard is recommended to maintain measurement integrity.