Description
Product Overview
The Mitutoyo 103-139 is a 50–75 mm outside micrometer built to the exacting standards that have made Mitutoyo the benchmark for toolroom metrology across Australia and the world. With a 0.01 mm graduation and a classic mechanical thimble design, this is a dependable, no-nonsense bench instrument for anyone who needs repeatable, accurate measurement in the 50–75 mm range — whether that’s checking turned stock, verifying bearing journal diameters, or qualifying ground shafts before assembly.
- 50–75 mm measuring range with 0.01 mm graduation — The 25 mm spindle travel covers the most common mid-range shaft and bore work without requiring a setting standard for every reading. The 0.01 mm (half-thou) graduation is fine enough for most toolroom and production applications without introducing the parallax sensitivity of a vernier micrometer.
- Carbide-tipped anvil and spindle faces — Mitutoyo equips this series with hardened carbide measuring faces, which resist wear and maintain flatness far longer than unhardened steel. This matters on a used tool: the faces are the first place accuracy is lost, and carbide tips mean there’s genuine working life left in a well-kept instrument.
- Lockable thimble with friction ratchet — The ratchet stop (visible on the thimble end) ensures consistent measuring force regardless of operator, which is critical for repeatable results across a shift or between operators on a shared bench. The spindle lock lever lets you secure a reading before pulling the mic from the part.
- Setting standard / reference gauge included — The 50 mm setting standard in the case allows you to zero and verify the instrument at the bottom of its range on the bench, rather than relying on a wrung slip stack. This is the correct way to verify a mid-range mic and is a genuine accessory, not an afterthought.
- Ideal for — Checking turned shaft diameters and bearing journals in the 50–75 mm range, qualifying ground spigots and bores (with a bore mic for comparison), verifying stock removal on a lathe between passes, checking hydraulic cylinder rod diameters, and qualifying press-fit component dimensions prior to assembly.
Condition
Used (Good Condition / Pre-Owned, Functionally Sound)
This micrometer presents in honest used condition consistent with having seen genuine workshop service. The frame carries the light surface patina and minor handling marks typical of a tool that’s been on the bench and done real work — no deep gouges, no impact damage, and no corrosion on the precision surfaces. The spindle advances and retracts smoothly throughout its full 25 mm travel with no binding or roughness, the ratchet stop engages cleanly with consistent feel, and the spindle lock holds a setting firmly. The measuring faces — both anvil and spindle — show no visible pitting, scoring, or edge chipping that would compromise contact geometry. The thimble scale and sleeve markings are clear and legible with no obscuring wear. As with any pre-owned precision instrument, we recommend zeroing against the included 50 mm setting standard and checking repeatability across several closures before putting the tool into production use. If your application demands traceable calibration, a straightforward calibration check against a certified ring gauge or master will confirm the instrument’s accuracy to your required standard.
Included
- 1 x Mitutoyo Outside Micrometer, 103-139, 50–75 mm, 0.01 mm graduation
- 1 x 50 mm setting standard / reference gauge
- 1 x Original Mitutoyo fitted case
- 1 x Original warranty / documentation card (保証書)
- 1 x Spanner / adjusting tool (as included in original accessory pack)
Not Included
- No additional setting standards beyond the 50 mm gauge
- No calibration certificate (recommend independent verification if traceability is required)
Brand Information
Mitutoyo Corporation, founded in Japan in 1934, is the world’s largest manufacturer of precision measuring instruments and is widely regarded as the global reference standard in dimensional metrology. Their products are manufactured in Japan to tolerances that consistently meet or exceed JIS and ISO 9000 series quality requirements, and Mitutoyo instruments are found in toolrooms, quality labs, and on CNC machine floors across Australia and internationally. In terms of market positioning, Mitutoyo sits at the top tier of the industry alongside Mahr and Starrett — a significant step above import-grade instruments and the tool of choice when accuracy and long-term reliability are non-negotiable.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model | 103-139 |
| Type | Outside Micrometer (Mechanical) |
| Series | 103 — Standard Outside Micrometer |
| Measuring Range | 50–75 mm |
| Graduation / Resolution | 0.01 mm |
| Accuracy | ±0.004 mm (per Mitutoyo Series 103 specification) |
| Measuring Faces | Carbide-tipped anvil and spindle |
| Spindle Thread Pitch | 0.5 mm |
| Measuring Force | Controlled via friction ratchet stop |
| Spindle Lock | Yes — lever type |
| Frame Material | Cast steel with enamel finish (heat-insulating side plates not specified on this series) |
| Country of Origin | Japan |
| Condition | Used (Good Condition) |
| Included Items | Micrometer, 50 mm setting standard, original fitted case, documentation, adjusting spanner |
| Not Included | Calibration certificate |
Keywords
Mitutoyo 103-139, Mitutoyo outside micrometer, Mitutoyo 50-75mm micrometer, outside micrometer 50-75mm, 0.01mm micrometer, toolroom micrometer Australia, precision micrometer used, shaft diameter measurement, machinist micrometer, Mitutoyo micrometer Australia, bore and shaft measurement, mechanical micrometer 75mm
