Description
Mitutoyo 20–25mm Holtest Internal Micrometer — Series 368-706
The Mitutoyo Holtest 368-706 is a three-point internal micrometer purpose-built for accurate bore measurement in the 20–25mm range. Unlike a two-point bore gauge or a telescoping gauge that relies on feel and a follow-up outside micrometer reading, the Holtest contacts the bore wall at three equally spaced anvils simultaneously, self-centring in the bore and delivering a direct, repeatable reading on the thimble. That means less operator dependency, faster setups, and genuine toolroom-grade repeatability without needing a second instrument to translate the measurement.
- Three-point self-centring contact system — The tri-anvil head centres itself in the bore automatically, eliminating the rocking technique required with two-point instruments. On the shop floor this translates to consistent readings between operators and far less re-measuring when verifying bored holes, reamed diameters, or honed cylinder bores.
- 0.005mm graduation on a direct-reading thimble — At half a thou per division, the Holtest resolves detail that a dial bore gauge or a telescoping gauge simply cannot match without additional equipment. This level of resolution is appropriate for checking H7/g6 fits, confirming bearing housing bores, or qualifying a finish-bored hole before assembly.
- 20–25mm measuring range — a critical bore size bracket — This range covers a high proportion of precision engineering work: 20, 22, 24, and 25mm reamed or bored features are common in hydraulic components, spindle housings, small gearboxes, and fixture tooling. Having a dedicated instrument for this range avoids interpolating across a wider-range gauge where sensitivity can be compromised at the extremes.
- Mitutoyo build quality — ground anvils, hardened measuring faces — The contact anvils are carbide-tipped and precision-ground, meaning wear from repeated use in cast iron, steel, and aluminium bores remains minimal over the tool’s service life. The thimble mechanism is the same quality standard used across Mitutoyo’s 300-series bore measuring range.
- Ideal for — Qualifying finish-bored and reamed holes on a manual lathe or machining centre, checking bearing housing diameters, verifying hydraulic cylinder bores, confirming bushing and liner fits, and incoming inspection of purchased components with 20–25mm internal features.
Condition
Used (Good Condition / Tested and Accurate)
This Holtest has been inspected and tested — the thimble turns smoothly with no binding, no backlash beyond normal micrometer tolerance, and the ratchet stop functions correctly. The three anvils extend and retract evenly with no sticking, and the measuring faces show no visible pitting, chipping, or deformation. The barrel and thimble graduations are clean and legible. There is light surface patina consistent with a tool that has seen regular workshop use — expect minor handling marks on the barrel and the outer sleeve, nothing that affects the precision surfaces or the measuring function. The instrument has been seller-verified as accurate; however, as is standard practice with any used precision bore micrometer, Makers Market recommends zeroing the instrument against a certified setting ring in the 20–25mm range prior to production use. Setting rings are not included with this listing but are available separately — see the seller’s note below.
Included
- 1 x Mitutoyo Holtest Three-Point Internal Micrometer, 20–25mm, Series 368-706
- 1 x Original Mitutoyo wooden storage case
- 1 x Original operation manual / papers
- Original Mitutoyo accessories as supplied (plastic bag, as pictured)
Not Included
- Setting ring (sold separately — required for zero verification and recommended before production use)
Brand Information
Mitutoyo Corporation is a Japanese precision instrument manufacturer founded in 1934 and widely regarded as the global benchmark in hand-held metrology. Their instruments are manufactured in Japan to rigorous JIS and ISO standards and are the reference point against which most other precision measuring tools in the industry are evaluated — sitting clearly above mid-market Chinese and Taiwanese brands and alongside Tesa (Switzerland) and Mahr (Germany) at the top tier of the global metrology market. In Australian toolrooms and machine shops, Mitutoyo is the dominant brand — calibration labs, TAFE machining departments, and tier-one manufacturers specify it as standard, which also means recalibration and service are straightforward to arrange locally.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model / Series | Holtest 368-706 |
| Type | Three-point internal micrometer (Holtest) |
| Measuring Range | 20–25mm |
| Graduation / Resolution | 0.005mm |
| Accuracy | ±0.006mm (per Mitutoyo specification for this series) |
| Contact System | Three-point self-centring, carbide-tipped anvils |
| Reading Type | Analogue thimble / barrel (vernier-style) |
| Construction | Hardened steel, ground precision surfaces, carbide contacts |
| Country of Origin | Japan |
| Condition | Used — Good Condition, tested and accurate |
| Included Items | Instrument, original wooden case, operation manual, original accessories |
| Not Included | Setting ring (sold separately) |
Keywords
Mitutoyo 368-706, Mitutoyo Holtest, Mitutoyo internal micrometer, three point bore micrometer 20-25mm, bore mic 20mm 25mm, Holtest bore gauge, internal micrometer toolroom, precision bore measurement, bore micrometer Australia, Mitutoyo used bore gauge, machining centre bore inspection, bearing housing bore measurement
