2-Point Internal Micrometer Holtest Set

Mitutoyo 368-907 - 2-point Holtest internal micrometer set 3-6 mm
The Mitutoyo 368-907 is a small diameter micrometer set from the Holtest series designed for precise internal measurement, offering highly accurate and repeatable measurements in situations where the internal diameter is very small and difficult to access with other measuring instruments. This model covers a measurement range of 3-6 mm, making it one of the most specialized and accurate solutions on the market for small hole and bushing measurements. The Mitutoyo 368-907 uses carbide-tipped, micro-finished measuring surfaces that resist abrasion and provide a smooth measuring contact. Small holes are particularly susceptible to surface damage and cracking, and therefore measuring surfaces must be highly precision ground and durable. A hallmark of the Holtest range is the sensitivity of the mechanical design of the instrument, which is particularly evident in the models covering small measuring ranges.
The philosophy behind the Holtest series is that the measuring instrument enables direct and mechanical measurement of the inside diameter without the need for complex dial gauges or fitting pieces. The measuring heads supplied with the set cover the entire 3-6 mm range, and the sensitivity of the mechanical design of the instrument makes it a reliable tool for both everyday workshop use and precision measurements in the laboratory.
When the gauge is placed in a 3-6 mm hole diameter, the two measuring surfaces contact the hole from opposite sides. The measuring screw is rotated until the ratchet-stop produces a characteristic light click, indicating that the measuring force is correct. Unlike outside micrometers, it is important that the measuring force is constant for inside diameters - even a small difference in compression can cause an incorrect reading with such small dimensions. The ratchet-stop makes this automatic and consistent by repeating the same force at each measurement.
Once the correct contact force is achieved, the measurement can be read directly from the micrometer scale. The measurement resolution extends to 0.001 mm, which is very important in this size range where even a small deviation can cause fit problems, product malfunction, or rejection by quality control.
Includes:
- 1 pc = 3-4 mm
- 1 pc = 4-5 mm
- 1 pc = 5-6 mm