Description
Product Overview
This Mitutoyo 368-904 Holtest set puts a full 50–100mm internal measuring capability on your bench in one hardwood case. Five three-point bore micrometers paired with three calibrated setting rings, an extension tube, and an adjustment tool kit — everything a toolroom needs to hold tight tolerances on bores, bushings, cylinders, and housings without swapping between instruments. The three-point contact design self-centres in the bore, eliminating the angular error that plagues two-point bore gauges and giving you a true diameter reading, not a chord measurement.
- Three-point self-centring anvil system — Unlike a two-jaw bore gauge or single-point inside mic, the three equally-spaced carbide-tipped contacts automatically locate on the bore centreline. This means you’re reading true diameter without needing to rock and hunt for the minimum — critical when you’re holding H7 fits or checking cylinder liner wear.
- 50–100mm range across five instruments — Each head covers a specific sub-range within the 50–100mm envelope, keeping the measuring range per instrument tight and maintaining accuracy across the full span. You’re not stretching a single gauge across 50mm of range and hoping for the best — each unit is optimised for its slice of the range.
- Mechanical thimble-and-barrel readout — No batteries, no display drift, no USB calibration cables. On the shop floor, a mechanical Holtest reads reliably in coolant mist, under fluorescent lights, or in the pit of a diesel workshop. Resolution is 0.001mm — sufficient for the vast majority of fit-and-function bore checking in this size range.
- Supplied with matched setting rings (3 rings) and extension tube — Setting rings are the correct way to zero a Holtest; they provide a certified ground-bore reference that a gauge block stack or a ring spanner cannot replicate. The extension tube allows reach into deep bores and blind housings where a standard head won’t seat squarely.
- Ideal for — Checking bearing housing bores to H7/H6 tolerances, verifying cylinder liner internal diameter on engine rebuilds, qualifying hydraulic cylinder bores, inspecting bushing press fits, and incoming QC on cast or machined housings where a plug gauge gives pass/fail but you need the actual number.
Condition
Used (Good Condition / Full Working Set)
Each micrometer has been inspected and lubricated. A total of 2 individual moving anvils were found to be sticky in their return which have been cleaned & freed up. Sold as working well in used condition. No damage has been found.
The five Holtest heads are in good used condition — the thimbles rotate smoothly with no detectable play, the barrel graduations are clean and legible across all instruments. The precision measuring surfaces on the carbide anvil tips show normal service wear consistent with a working toolroom instrument; there are no chips, flat spots, or deformation evident.
The setting rings show visible patina and small surface oxidation spots on their bore measuring faces, which is typical for older steel rings. Importantly, patina on the outer face and ring body is cosmetic only; what counts is the condition of the internal ground bore surface. The seller notes the rings remain usable and accurate when positioned correctly to find the clean bearing surface.
The wooden Mitutoyo case is intact and functional, holding all instruments securely in the original foam. The extension tube and adjustment tool kit are present. This is a practical, ready-to-use set that will serve a busy shop floor or well-equipped home toolroom without reservation — it just may not be the set you’d submit to a NATA-accredited lab without first reconditioning the setting rings.
Included:
- 5 x Mitutoyo Holtest Three-Point Internal Micrometers, 50–100mm (Series 368-904)
- 3 x Mitutoyo Setting Rings (matched to the set)
- 1 x Extension Tube
- 1 x Adjustment Tool Kit
- 1 x Mitutoyo Certificate of Calibration
- 1 x Original Mitutoyo Wooden Storage Case
Not included:
- No additional setting rings or masters beyond the 3 supplied
Shipping
$15.95 Flat-rate shipping not available — bulky item rate of $29.95
Brand Information
Mitutoyo Corporation is Japan’s largest manufacturer of precision measuring instruments and holds a position at the very top of the global metrology market — sitting alongside Mahr, Carl Zeiss, and Starrett as the benchmark against which other brands are measured. Founded in 1934 in Kawasaki, Japan, Mitutoyo instruments are found in aerospace, automotive, defence, and precision machining facilities worldwide precisely because their manufacturing tolerances, material quality, and calibration traceability are genuinely production-grade rather than aspirational. When you pick up a Mitutoyo Holtest, you’re holding an instrument built to the same standard as the instruments used to verify it.
Specifications
| Feature | Specification |
|---|---|
| Brand | Mitutoyo |
| Model / Series | 368-904 Holtest |
| Type | Three-Point Internal Micrometer (Holtest) |
| Measuring Range (Set) | 50–100mm (5 heads covering sub-ranges within this span) |
| Graduation / Resolution | 0.001mm |
| Measuring Principle | Three-point self-centring contact — reads true diameter |
| Contact Points | Carbide-tipped, three-point equilateral arrangement |
| Setting Method | Setting rings (3 x matched rings supplied) |
| Accessories Included | 3 setting rings, extension tube, adjustment tool kit, calibration certificate, wooden case |
| Case | Original Mitutoyo wooden storage case |
| Country of Origin | Japan |
| Condition | Used — Good Condition; setting rings show patina, verify before use as calibration master |
| Calibration Certificate | Included (Mitutoyo — verify currency for your quality system requirements) |
| Shipping Note | Bulky item — flat-rate shipping not applicable; separate freight quote required |
Keywords
Mitutoyo 368-904, Mitutoyo Holtest set, three-point bore micrometer 50-100mm, internal micrometer set, bore mic, Holtest bore gauge, toolroom bore measuring, Mitutoyo internal micrometer, bore gauge with setting rings, cylinder bore measurement, precision bore micrometer Australia, machining bore inspection
