Description
Product Overview
The Mitutoyo Holtest 368-172 is a three-point internal micrometer covering the 75–88mm range, built to Mitutoyo’s exacting toolroom standards. Unlike a two-point bore mic or a telescoping gauge that depends on feel and a follow-up measurement with an outside mic, the Holtest self-centres in the bore via three equally spaced contact points — giving you a direct, repeatable reading at the true diameter without the operator-induced error that plagues two-jaw alternatives. If you’re chasing H7 fits, checking cylinder bores after a rebore, or qualifying a bored housing before pressing in a bearing, this is the instrument that belongs on your bench.
- Three-point self-centring contact system — direct reading, no transfer error. The three tungsten carbide-tipped anvils locate automatically at the bore’s true centre, eliminating the rocking and transfer steps required with a two-point mic. For toolroom work where you need repeatable readings to 0.005mm graduation, this design removes the biggest single source of human error.
- 0.005mm graduation with ±0.003mm accuracy — genuine toolroom resolution. At this specification, verified to Mitutoyo standard and backed by the included certificate of inspection, the 368-172 is capable of confirming interference and transition fits in bearing and bushing work — not just checking whether a bore is “close enough”.
- 75–88mm range in a single head — covers the most common bearing housing and cylinder bore sizes. This range catches 80mm, 85mm, and common metric bearing OD housings in one instrument without a range extension. The thimble reads directly off the graduated sleeve in the same familiar way as any outside mic, so there’s no relearning your reading technique.
- Compatibility and accessories. The Holtest is used directly in the bore — no stand or indicator is required. A setting ring at the nominal size (75mm, 80mm, or 85mm) is the correct way to zero the instrument; setting rings are available separately. The included certificate lists the inspection points at 75mm, 80mm, and 88mm.
- Ideal for: checking bored housings for bearing press fits, qualifying cylinder bores after line boring or honing, verifying hydraulic cylinder and sleeve bores, inspecting bushing housings on jig bores and horizontal borers, and confirming H7/h6 or H6/k5 fits in production or toolroom environments.
Condition
(Used — Like New / Excellent Mechanical Condition, Minimal Use)
This Holtest presents exceptionally well for a used instrument. The three carbide anvil faces are clean and free of nicks or scoring — the contact surfaces that matter most are in sound shape. The thimble rotates smoothly with no detectable play, the graduated sleeve is clearly legible with no wear to the markings, and the ratchet stop functions correctly, delivering consistent measuring force as intended. The chrome and satin surfaces show no meaningful wear patina — this tool has clearly had very little bench time. The seller describes it as well cared for, and the physical condition is consistent with that assessment. As with any used precision instrument, best practice is to verify zero against a calibrated setting ring at one or more points in the range before putting it to work — the included certificate of inspection documents factory performance, but confirming current zero is straightforward and takes two minutes. No functional deficiencies were identified.
Included:
- 1 x Mitutoyo Holtest Three-Point Internal Micrometer, Model 368-172, 75–88mm, 0.005mm graduation
- Original Mitutoyo hard plastic carry case
- Certificate of Inspection (issue no. 08J1001B, serial no. 844667)
- Original instruction / reference papers
- Original accessories as supplied by Mitutoyo
Not included:
- Setting rings (available separately — strongly recommended for zeroing)
Brand Information
Mitutoyo Corporation, founded in Japan in 1934, is the global benchmark in hand-held precision measurement instrumentation — the name machinists reach for when the reading actually matters. Their products are manufactured in Japan to tolerances that consistently meet or exceed stated accuracy, and Mitutoyo’s quality system and traceability standards are recognised worldwide. In the metrology market, Mitutoyo sits alongside Mahr, Tesa, and Starrett at the top of the field — a step above the mid-tier Taiwanese and Chinese instruments and a direct competitor to other Japanese marques like Mitutoyo’s own RSK range and Fowler. Buying a used Mitutoyo instrument in good condition is, for most Australian toolrooms and home shops, a significantly better investment than a new budget-brand equivalent.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model | 368-172 (HT-8SR per certificate) |
| Type | Holtest Three-Point Internal Micrometer |
| Series | 368 — Holtest (current / modern production) |
| Measuring Range | 75–88mm |
| Graduation / Resolution | 0.005mm |
| Permissible Error (Accuracy) | ±0.003mm (±3µm) per certificate of inspection |
| Uncertainty of Measurement | U = 2.5µm (k = 2) per certificate |
| Standard Temperature | 20°C |
| Contact Points | Three-point, self-centring, tungsten carbide tipped |
| Inspection Standard | Mitutoyo standard |
| Serial Number | 844667 |
| Country of Origin | Japan |
| Condition | Used — Like New / Excellent, minimal use |
| Included Items | Instrument, original hard case, certificate of inspection, instruction papers, original accessories |
| Not Included | Setting rings (sold separately) |
Keywords
Mitutoyo 368-172, Mitutoyo Holtest, Mitutoyo internal micrometer, Holtest 75-88mm, three-point bore micrometer, bore mic 75mm, internal micrometer toolroom, Holtest bore gauge, precision bore measurement, bearing housing inspection, cylinder bore micrometer, Mitutoyo Japan metrology
