Description
Condition
Used (Good).
This internal micrometer is in good condition, presenting well aesthetically and functioning perfectly. The mechanical movement is smooth, and the ratchet stop provides the correct tactile feedback. It is housed in its original manufacturer’s wooden storage case, which provides excellent protection.1 Please Note: This listing is for the micrometer and case only; it does not include a setting ring or adjustment spanner.
Product Overview
The Mitutoyo 368-109 is a professional-grade “Holtest” (Hole Test) internal micrometer designed for precise bore measurements in the 45mm to 50mm range. This mechanical instrument utilises a three-point self-centring contact system, widely regarded as the most stable method for internal measurement. As the spindle is rotated, three hardened anvils extend radially to contact the bore wall, automatically aligning the tool with the axis of the hole to ensure accuracy. The measurement is read via a clear, satin-chrome finished vernier scale on the thimble. It features a ratchet stop mechanism to ensure constant measuring force, eliminating variations caused by different operator strengths.2 The anvils are designed to allow measurement close to the bottom of blind holes, adding to its versatility in complex machining setups.3
Brand Information
Mitutoyo Corporation is the world’s leading manufacturer of precision measuring instruments, established in Japan in 1934.4 The “Holtest” series is iconic within the metrology industry, setting the standard for internal diameter measurement. Mitutoyo is renowned for its exacting manufacturing tolerances and high-quality metallurgy, ensuring that its mechanical tools remain accurate and reliable over decades of service.5 The 368 series demonstrates their commitment to producing robust, workshop-ready tools that professional machinists can trust for critical engine and component measurements.
Specifications
| Feature | Specification |
| Model | 368-109 |
| Measuring Range | 45mm – 50mm |
| Graduation | 0.005mm |
| Accuracy | ±3µm |
| Measuring Method | 3-Point Self-Centring |
| Display | Vernier Scale (Mechanical) |
| Mechanism | Ratchet Stop (Constant Force) |
| Case Type | Original Wooden Case |
| Included Accessories | None (Micrometer & Case Only) |
Keywords
Mitutoyo, 368-109, Holtest, internal micrometer, bore micrometer, 45-50mm gauge, three-point micrometer, blind hole measurement, mechanical bore gauge, Japanese metrology, machinist tools.
