Description
Mitutoyo 368-904 Holtest Three-Point Internal Micrometer Set — 50–100mm
The Mitutoyo 368-904 Holtest is a professional-grade three-point internal micrometer set covering the 50–100mm bore measurement range across five individual gauges. Unlike two-point bore gauges that rely on feel and operator technique to find the true diameter, the Holtest’s three-contact measuring system self-centres in the bore, giving you a direct reading that’s repeatable, reliable, and independent of skew. This is toolroom-grade kit built for the bench — and this example presents in exceptional condition with minimal evidence of workshop life.
- Three-point self-centring contact system — Three tungsten carbide-tipped anvils make simultaneous contact with the bore wall, automatically centring the instrument along the true diameter. You eliminate the rocking and tilting technique required with a two-point bore gauge, which means less operator-to-operator variation and more confidence in the number you’re reading — critical when you’re chasing a tight H7 fit or verifying a reamed hole before assembly.
- 0.001mm graduation across the full 50–100mm range — Resolution to one micron lets you detect stock removal in the single-digit micron range. On a finishing pass or a honing operation where you’re creeping up on final size, that granularity tells you what’s actually happening in the bore rather than forcing you to interpolate between marks.
- Direct-reading micrometer thimble — no transfer to a comparator required — Unlike a telescoping gauge or small bore gauge that must be removed and measured externally, the Holtest reads directly in the bore. That removes one complete source of error (the transfer step) and significantly speeds up in-process gauging on a lathe, mill, or cylindrical grinder.
- Set of five gauges with Mitutoyo setting rings — Each gauge covers a sub-range within 50–100mm, and the kit includes the corresponding Mitutoyo setting rings for zero-setting each instrument against a ground reference of known size. The rings are the correct way to establish zero — far more reliable than setting against a micrometer jaw or a bore of unknown accuracy.
- Ideal for — Verifying bored, reamed, or honed diameters on the lathe or machining centre; checking cylinder liner and housing bores in engine reconditioning; qualifying hydraulic cylinder bores; in-process gauging during internal grinding; QC inspection of bearing housings and gearbox cases where fit class matters.
Condition
Used (Like New / Immaculate, Minimal Use)
This kit presents in exceptional condition that is genuinely difficult to distinguish from new old stock. All five Holtest gauges show no measurable wear on the carbide anvil tips, no corrosion, no pitting, and no visible handling marks on the thimbles or barrels — the anodised and ground surfaces are clean and bright throughout. The three Mitutoyo setting rings are equally unmarked: the precision-ground bore faces show none of the fretting or contact wear that accumulates on rings that have seen regular service, and there is no rust bloom or surface oxidation on any ring. The original wooden storage case is intact, with the kraft paper packing undisturbed in a way consistent with a kit that has been stored correctly rather than knocked around a toolroom. Mechanically, the thimble action on each gauge is smooth and free from slack or binding, and the locking collars function correctly. As with any used precision instrument — regardless of apparent condition — best practice before putting this kit into production is to zero each gauge against its corresponding setting ring and verify the reading against a known bore or gauge block stack. That single step will confirm calibration status and give you confidence in the readings before the first chip falls.
Included
- 5 x Mitutoyo Holtest Three-Point Internal Micrometer (368-904 set, covering 50–100mm range across five gauges)
- 3 x Mitutoyo precision setting rings (sized to correspond to the gauge sub-ranges within the set)
- Original Mitutoyo wooden storage case
- Original packing and accessories as supplied by Mitutoyo
Not Included
- Current calibration certificate — recommend calibration verification against traceable standards before use in a formal QC environment
Brand Information
Mitutoyo Corporation, founded in Japan in 1934, is the largest manufacturer of precision measuring instruments in the world and is widely regarded as the benchmark brand in dimensional metrology — sitting at the top of the same tier as Mahr, Tesa, and Starrett for professional and toolroom-grade instrumentation. Their Holtest series has been the go-to three-point internal micrometer in toolrooms and inspection departments across Asia-Pacific for decades, trusted in aerospace, automotive, and precision engineering environments where traceability and repeatability are non-negotiable. Japanese-made Mitutoyo instruments are a genuine selling point: tight manufacturing tolerances, consistent quality control, and long service life with minimal maintenance are well-documented characteristics of the brand in practice.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model / Series | Holtest — Series 368, Set No. 368-904 |
| Type | Three-point internal micrometer (bore gauge, direct reading) |
| Measuring Range (Set) | 50–100mm (five gauges covering sub-ranges within set) |
| Graduation / Resolution | 0.001mm (1 micron) |
| Accuracy | ±0.003mm (refer to Mitutoyo Series 368 specification sheet for per-range values) |
| Contact Points | Three-point, tungsten carbide tipped, self-centring |
| Setting Method | Precision setting rings (included) |
| Number of Gauges in Set | 5 |
| Setting Rings Included | 3 x Mitutoyo precision setting rings |
| Country of Origin | Japan |
| Storage / Case | Original Mitutoyo wooden case (included) |
| Condition | Used (Like New — minimal use, immaculate throughout) |
| Included Items | 5 x Holtest gauges, 3 x setting rings, original wooden case, original accessories and packing |
| Not Included | Current calibration certificate |
Keywords
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