Description
Product Overview
The Mitutoyo Holtest 368 Series is one of the most respected internal micrometer systems on the market — a three-point contact bore mic that self-centres in the bore and delivers repeatable, reliable readings without the operator-induced error that plagues two-point internal mics. This example is a 25–30mm H1 head, a workhorse range covering the bores most commonly encountered in general machining: bearing housings, bushing bores, hydraulic cylinder liners, and precision-fit holes in fixtures and dies.
- Three-point self-centring contact system — Unlike a two-jaw telescoping gauge or a standard two-anvil bore mic, the three-point Holtest design centres itself in the bore automatically. This eliminates the rocking and feel-dependent technique required with other internal mics, delivering consistent readings regardless of operator experience — critical when you’re checking a bearing housing to a 0.01mm tolerance and can’t afford a re-bore.
- 0.005mm graduation (1 DIV = 0.005mm) — Visible on the thimble scale in the photo, this half-micron resolution puts you firmly in toolroom territory. For bore work where clearance fits are measured in single-digit microns, reading to 0.005mm means you’re not guessing at the half-thou mark.
- 25–30mm measuring range (H1 head) — The H1 designation covers the 25–30mm range, one of the most frequently used spans in general machining. This range spans common bearing IDs (6205, 6305 series bearings sit at 25mm bore), bronze bushings, and precision dowel holes in tooling plate.
- Mitutoyo 368 Series compatibility — The H1 head is designed to be used with a Mitutoyo Holtest handle from the 368 Series system. Per the seller’s notes, this head is stored in a box sized for another range — confirm handle compatibility against the Mitutoyo 368 Series catalogue before use. Replacement handles and setting rings are available through Mitutoyo AU distributors.
- Ideal for — Checking bearing housing bores on a surface plate, verifying cylinder liner IDs, inspecting precision bushing fits in hydraulic manifolds, confirming reamed hole diameters in jigs and fixtures, and final inspection of bored features on a machining centre or lathe.
Condition
Used (Good Condition)
The measuring surfaces and three-point contact head show no visible damage, gouging, or wear that would affect measurement integrity — the contact points are the critical surfaces on a Holtest, and these present cleanly in the photos. The thimble and barrel graduation markings are clear and legible. The tool shows the kind of light surface patina consistent with careful storage and previous calibrated use in a toolroom environment — not abuse, just honest service life. The seller notes this H1 head has been stored in a 368 Series box sized for a different range, so treat the box as protective packaging rather than a matched set; confirm the measuring range against the head markings (25–30mm) before use. A calibration certificate is included, which is a meaningful inclusion for any tool going back into a quality-controlled environment — verify the certificate date and issuing body against your shop’s calibration interval requirements. As with any used bore mic returning to service, zeroing against a certified setting ring or a traceable master gauge before first use is recommended practice, regardless of the certificate.
Included
- 1 x Mitutoyo Holtest H1 Head — 25–30mm, 368 Series, 0.005mm graduation
- Original wooden storage box (368 Series — note: sized for a different range within the series)
- Papers / manuals
- Calibration certificate
- Original accessories (as packed — see photos)
Not Included
- Mitutoyo Holtest handle (sold separately — required for use; source a 368 Series compatible handle through Mitutoyo AU distributors)
- Setting ring / master gauge (recommended for in-service zero verification; not included)
Brand Information
Mitutoyo Corporation, founded in Japan in 1934, is the benchmark name in precision metrology worldwide — sitting at the top tier of the market alongside Mahr, Tesa, and Starrett. Their toolroom-grade instruments are manufactured to exacting Japanese Industrial Standards and are the default specification on quality inspection floors across aerospace, automotive, and precision engineering globally. In Australia, Mitutoyo instruments are supported through an established local distribution and calibration network, making spares, setting rings, and recalibration services genuinely accessible — a practical advantage over lesser-known imported brands.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model / Series | Holtest 368 Series — H1 Head |
| Type | Three-point internal micrometer (Holtest head) |
| Measuring Range | 25–30mm |
| Graduation / Resolution | 0.005mm (1 DIV = 0.005mm) |
| Accuracy | Refer to calibration certificate and Mitutoyo 368 Series datasheet (typically ±0.003mm for this range — verify against certificate) |
| Contact System | Three-point self-centring |
| Handle Compatibility | Mitutoyo 368 Series handle (not included — required for use) |
| Material / Construction | Hardened steel contact points, aluminium / steel body |
| Country of Origin | Japan |
| Condition | Used — Good Condition |
| Included Items | H1 head, wooden box, papers/manuals, calibration certificate, original accessories |
| Not Included | 368 Series handle, setting ring / master gauge |
Keywords
Mitutoyo Holtest 368, Mitutoyo internal micrometer, Mitutoyo bore mic 25-30mm, Holtest H1 head, three-point internal micrometer, bore micrometer Australia, toolroom bore gauge, internal mic 25mm, Mitutoyo 368 series, precision bore measurement, machining centre bore inspection, used Mitutoyo micrometer Australia
