Spi 21-904-8 Mechanical Hole Micrometer 0.8-1.0 in

Product Description

The SPI 21-904-8 is a mechanical hole micrometer designed for precision internal bore measurement in the range of 0.8000 to 1.0000 inches. It delivers an accuracy of 0.0001 inches (0.002 mm) with a graduation of 0.0002 inches, making it suitable for tight-tolerance machining and inspection work. The micrometer features three self-centering contact points with carbide measuring surfaces and a ratchet stop thimble for consistent, repeatable gauging pressure. Machinists, quality control technicians, and tool and die professionals use this instrument wherever bore diameter verification is required to a high degree of precision.

The 21-904-8 is appropriate for use in precision manufacturing, machine shop inspection, and tool room environments. It handles internal measurements where standard outside micrometers or bore gauges lack the resolution needed for close-tolerance work. The instrument comes with a setting ring with a 1.0000-inch diameter and one extension rod with a maximum extension rod length of 6.0000 inches, expanding its utility across a range of bore depths up to 3.5500 inches gauge depth. A NIST traceability certification is included, making it suitable for calibrated inspection processes.

Key Features

• Measurement range of 0.8000 to 1.0000 inches with 0.0001-inch accuracy
• Three self-centering contact points for repeatable, centered readings
• Carbide measuring surfaces for extended wear resistance
• Ratchet stop thimble provides consistent gauging pressure
• Chrome finish on micrometer body
• Includes setting ring and one extension rod; NIST traceability certification included

Compatibility

Designed as an OEM-style precision measuring instrument for internal bore gauging applications requiring a 0.8000 to 1.0000 inch measurement range in machine shop, tool room, and quality control inspection settings.

Installation Notes

This instrument is installed and operated by machinists or metrology technicians familiar with precision measuring equipment. Before use, verify calibration with the included setting ring per the manufacturer procedure. Keep measuring surfaces clean and free of chips or debris prior to each measurement. Store in the provided case away from temperature extremes to maintain calibration integrity.