Description
Mitutoyo 25–30mm Holtest Three-Point Internal Micrometer — 368-107
The Mitutoyo Holtest is the benchmark three-point internal micrometer for toolroom and production floor alike. This 25–30mm example (Series 368-107) gives you direct-reading bore measurement across a 5mm span with self-centring, three-contact geometry — no rocking, no interpolation, just a repeatable reading right off the thimble. If you’re measuring bored housings, reamed holes, hydraulic cylinder bores, or finish-ground ID work where a two-point bore gauge won’t give you the geometry you need, this is the instrument that belongs on your bench.
- Three-point self-centring contact system — Unlike a two-jaw bore gauge that requires careful rocking to find true diameter, the Holtest’s three equally-spaced carbide contacts locate automatically on the bore centreline. This eliminates the single biggest source of operator error in internal measurement and gives you consistent, repeatable readings without technique-dependent skill.
- Direct micrometer thimble readout — Reads directly in 0.001mm increments off the sleeve and thimble — no dial face to interpret, no zeroing to a master and reading a deviation. Combined with the gold-ring thimble locking collar, you can lock the reading and extract the tool from a blind bore without disturbing the setting.
- 25–30mm measuring range — This 5mm span sits squarely in the range used daily for press-fit bearing housings, shaft seal bores, bushings, and small cylinder work. A compact, purpose-built range means the contact geometry is optimised for this span — you’re not stretching a general-purpose tool to cover a size it wasn’t designed for.
- Ideal for — Measuring finish-bored and reamed housings, checking bore size after honing or grinding, verifying hydraulic cylinder and pneumatic bore diameters, inspecting bearing housing fits, and confirming ID tolerances on turned or ground sleeves and bushings.
Condition
Used (Good Condition)
Mechanically, this Holtest is in good working order. The thimble turns smoothly with no binding or roughness through the full 25–30mm range, the three-point contact assembly extends and retracts correctly, and the locking ring functions as intended. The carbide contacts show no visible chipping or flat-spotting to the naked eye — the surfaces that actually do the measuring are the ones that count, and they present well. There is the expected light surface patina and minor handling marks on the barrel and body consistent with a used instrument that has been stored and used in a workshop environment rather than abused — nothing that affects geometry or function. One point to note: the tool is stored in its original Mitutoyo wooden case, however the seller advises this case is for an incorrect Holtest size — it fits and protects the instrument adequately, but the case labelling will not match the 368-107 specification. As is standard practice for any pre-owned precision internal micrometer, we strongly recommend verifying the zero and calibration against a certified setting ring in the 25–30mm range before putting this instrument into production inspection. Setting rings to suit this range are listed separately by the seller.
Included
- 1 x Mitutoyo Holtest Three-Point Internal Micrometer, 25–30mm, Series 368-107, Gold Ring (Locking Thimble) Model
- 1 x Original Mitutoyo wooden storage case (note: case is labelled for a different Holtest size — see condition notes above)
Not Included
- Setting ring (listed separately — required for calibration verification)
Brand Information
Mitutoyo Corporation, founded in Japan in 1934, is the world’s largest manufacturer of precision measuring instruments and the name that defines the top tier of production and toolroom metrology globally. Their instruments are manufactured to exacting standards in Japan and are the default specification on aerospace, automotive, and precision engineering inspection floors worldwide. Mitutoyo sits above catalogue-grade instrument brands and is the direct peer of Mahr, Tesa, and Starrett in terms of accuracy, build quality, and long-term calibration stability — with the added advantage of extensive AU-based service and calibration support.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model / Series | Holtest 368-107 |
| Type | Three-Point Internal Micrometer (Holtest) |
| Measuring Range | 25–30mm |
| Graduation / Resolution | 0.001mm |
| Accuracy | ±0.004mm (per Mitutoyo specification for this series) |
| Contact Type | Three-point self-centring, carbide-tipped contacts |
| Thimble Variant | Gold ring — locking thimble model |
| Material / Construction | Hardened steel body, carbide measuring contacts |
| Country of Origin | Japan |
| Condition | Used — Good Condition / Toolroom Patina |
| Included Items | Instrument; original Mitutoyo wooden case (labelled for alternate size — see condition notes) |
| Not Included | Setting ring (listed separately) |
Keywords
Mitutoyo Holtest 368-107, Mitutoyo internal micrometer, three-point bore micrometer 25-30mm, Holtest bore mic, internal micrometer Australia, bore gauge toolroom, Mitutoyo 368 series, precision bore measurement, bore mic 25mm 30mm, machinist internal gauge, toolroom micrometer used, bore micrometer bearing housing
