Description
Product Overview
Measuring small bores to genuine micron-level accuracy is one of the hardest jobs in the toolroom — and it’s exactly where the Mitutoyo Holtest earns its reputation. Unlike two-point bore gauges that rely on operator rocking to find the true diameter, the 3-point Holtest uses three self-centring anvils spaced at 120° to lock onto the bore axis automatically, giving you a repeatable reading every single time. In the tight 12-16mm range, this is the go-to tool for small hydraulic bores, precision bushing fits, valve guides, and injector bodies. This one also comes bundled with a reputable SK Japan 12mm setting ring — meaning you can zero and verify the mic right out of the gate.
- True 3-point self-centring via three TiN-coated anvils at 120° — automatically aligns on the bore axis with no operator feel required.
- 0.005mm graduation on the thimble for direct micron-level reading without interpolation.
- Titanium-nitride coated contact points resist wear and galling far better than bare steel — keeps accuracy over years of use.
- Ratchet stop delivers consistent measuring force, eliminating operator-induced error between readings.
- Includes SK 12mm setting ring (guaranteed to 0.0004mm accuracy) — use it to zero the mic and periodically verify calibration in-shop.
- Ideal for valve guide inspection, small hydraulic bores, precision bushing ID, injector components, and any tight-tolerance small-bore work.
Condition
Used (Good Working Condition / No Case).
Honest write-up here: this Holtest has been used — it’s not a shelf queen. Mechanically everything is sound: the three anvils extend and retract cleanly, the ratchet stop clicks properly, and the thimble turns smoothly throughout its range. The TiN-coated contact points show their characteristic gold colour with no visible wear-through or chipping. Cosmetic patina is consistent with shop use — some handling marks on the thimble and body — but nothing that affects function. No fitted case is supplied with this listing. Store it carefully or source a generic foam case to protect the anvils in transit. As always with used mics, we recommend zeroing against the supplied setting ring before first use.
The bundled SK Japan 12mm setting ring is a bonus here — SK (Niigata Seiki) is a Japanese metrology brand sitting in the same tier as Mitutoyo for reference gear, and the stated ±0.0004mm tolerance means you’ve got a legitimate calibration reference to go with the mic.
Included:
- 1 x Mitutoyo 3-Point Internal Micrometer (Holtest), 12-16mm, 0.005mm graduation
- 1 x SK (Japan) 12mm Setting Ring — accuracy within 0.0004mm
Not included: Original case
Brand Information
Mitutoyo is the global standard-bearer in precision metrology — founded in Tokyo in 1934 and the name that appears on virtually every serious toolroom bench in the world. Their Holtest three-point internal micrometer line has been the benchmark for small-bore measurement for decades; when engineers specify “3-point bore mic” they almost always mean a Holtest. The SK-branded setting ring supplied with this lot is from Niigata Seiki, another respected Japanese metrology manufacturer whose reference standards are widely used in Japanese industry for calibration and gauge verification.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Type | 3-Point Internal Micrometer (Holtest) |
| Model Family | Series 368 (Holtest) |
| Measuring Range | 12 – 16 mm |
| Graduation | 0.005 mm |
| Accuracy | ±3 μm |
| Measuring Method | 3-point self-centring (anvils at 120°) |
| Contact Points | Titanium-nitride (TiN) coated |
| Measuring Depth | ≈ 80 mm |
| Force Control | Ratchet stop |
| Country of Origin | Japan |
| Setting Ring | SK (Niigata Seiki) 12mm, accuracy ±0.0004mm |
| Condition | Used — Good Working Order |
| Included | Holtest mic, SK 12mm setting ring |
| Not Included | Case |
Keywords
Mitutoyo Holtest, Mitutoyo 3 point bore micrometer, 12-16mm internal micrometer, Mitutoyo 368 series, 3 point hole micrometer, small bore micrometer, Mitutoyo internal mic, SK setting ring, Holtest 12-16, self-centring bore micrometer, precision bore micrometer, TiN coated bore mic
