Mitutoyo 139-179 Tubular Inside Micrometer 4-36 in

Product Description

The MITUTOYO 139-179 is a mechanical tubular inside micrometer designed for accurate internal bore and diameter measurements across a wide range of 4 to 36 inches. Built around a hollow pipe design with interchangeable extension rods, it delivers a graduation of 0.001 inches for precise readings without a digital counter. Accuracy is rated at 0.00012 plus m plus (0.00004 x R/20) inches, making it a reliable choice for demanding measurement tasks in manufacturing, machining, and inspection environments. The set includes five extension rods covering 1, 2, 4, 8, and 16-inch lengths, giving technicians the reach needed for large-bore applications.

This micrometer is suited for professional use in machine shops, manufacturing facilities, and industrial maintenance settings where large internal dimensions must be verified with precision. The tubular body construction and interchangeable extension system allow a single tool to cover measurements from 4 to 36 inches, reducing the need for multiple instruments when working across varying bore sizes. It is intended for use by machinists, quality control inspectors, and metrologists who require consistent, repeatable inside measurement performance.

Key Features

• Wide measurement range of 4 to 36 inches using interchangeable extension rods
• Graduation of 0.001 inches for precise mechanical readout
• Hollow pipe tubular design with 5 extension rods: 1, 2, 4, 8, and 16 inches
• Maximum single extension rod length of 16 inches
• Rod diameter of 0.67 inches for stable extension coupling
• No digital counter — fully mechanical operation for reliable field use

Compatibility

Designed as an OEM-style inside micrometer for use with Mitutoyo 139-series tubular micrometer extension rod systems. No specific replacement part numbers were provided in the product data.

Installation Notes

This instrument is installed and operated by machinists or metrology technicians following standard calibration and measurement procedures. Before use, verify the tool is zeroed against a reference standard appropriate for the measurement range. Extension rods should be hand-tightened securely to prevent measurement error from loose couplings. Store the instrument in its case when not in use to protect the contact surfaces and extension rod threads.