Spi 10-742-5 Mechanical Hole Micrometer 2.4 Inch

Product Description

The SPI 10-742-5 is a mechanical hole micrometer designed for precision internal bore measurement. It features a ratchet stop thimble that delivers consistent measuring pressure, solid carbide measuring anvils for long-term wear resistance, and a self-aligning, self-centering three-contact-point design that seats accurately inside bores without manual adjustment. The instrument reads to a graduation of 0.0002 inches with an accuracy of 0.000250 inches, making it suitable for demanding dimensional inspection work in machine shops, maintenance facilities, and manufacturing environments. It is used by machinists, metrology technicians, and precision maintenance professionals.

This hole micrometer covers a maximum measurement range of 2.4 inches, with a gage depth of 3.54 inches and a maximum extension rod length of 6.0 inches. The setting ring diameter is 2.0 inches. It is well-suited for inspecting bores, cylinders, and internal diameters in production machining, engine rebuilding, pump service, and similar precision measurement applications where analog readout is preferred over digital instrumentation.

Key Features

• Ratchet stop thimble ensures repeatable, consistent measuring pressure across readings
• Solid carbide measuring anvils resist wear on hardened and abrasive workpiece surfaces
• Self-aligning and self-centering three-contact-point design seats accurately in bores
• 0.0002 inch graduation with 0.000250 inch accuracy for high-precision dimensional work
• Maximum extension rod length of 6.0 inches extends reach into deep bores
• No digital counter — direct analog thimble reading for straightforward interpretation

Compatibility

Designed as an OEM-style mechanical hole micrometer suitable for general internal bore measurement applications across machine shop, maintenance, and manufacturing environments where a 2.4 inch maximum range instrument is required.

Installation Notes

This instrument is used by machinists and metrology technicians and requires no installation in the traditional sense. Before use, zero the micrometer against the included or separately sourced setting ring to verify calibration. Handle carbide anvils carefully to avoid chipping against hard surfaces. Store in a protective case away from temperature extremes to maintain measurement accuracy.