3-point internal micrometer – SAM770

The 3-point internal micrometer is an instrument designed for the direct measurement of internal diameters on bores, recesses and cylindrical holes. This type of internal micrometer is widely appreciated when a stable, repeatable and immediate measurement is required together with a traditional mechanical reading. The 3-point micrometer is suitable for machine shops, tooling departments and quality control areas where different internal diameters must be checked using a dedicated instrument.

The measuring principle is based on a 3-point measuring head that works inside the bore. This configuration allows the instrument to contact the internal surface evenly. Compared to other internal micrometers, the 3-point version is intended for direct measurement without the need for comparative systems.

From a construction point of view, the micrometer features a ratchet thimble and carbide measuring contacts. The ratchet helps apply consistent measuring force, while the carbide contacts improve wear resistance during repetitive inspections. For users looking for an analogue internal micrometer, this configuration represents a reliable and practical solution for everyday workshop use.

The range covers measurements up to 300 mm, with different measuring ranges depending on the diameter to be checked. In the smaller ranges the reading is 0.001 mm, while in the larger ranges the reading is 0.005 mm. This allows the 3-point internal micrometer to maintain good operating practicality across the whole series.

Up to the 100 mm range, the instrument is supplied with a DIN 2250C setting ring and extension. The setting ring is used for correct zero adjustment before measurement, while the extension increases the measuring depth, making inspections easier in deeper holes. For ranges above 100 mm, the setting rings can be supplied separately on request. An ACCREDIA calibration certificate or a calibration report is also available on request.

From an operational point of view, this internal micrometer is recommended when different internal diameters must be checked using a dedicated instrument available in several measuring ranges. It is a suitable solution for users looking for 3-point internal micrometers that combine continuity of use with the possibility of increasing measuring depth by means of extensions.

Applications

• Measurement of internal diameters on bores and cylindrical seats
• Inspection of internal holes in general mechanics
• Dimensional checks of internal diameters up to 300 mm
• Direct measurement of diameters
• Workshop and quality control inspections

FAQ – 3-point internal micrometer

What is a 3-point internal micrometer?
It is a measuring instrument designed to check internal diameters on bores and holes using a three-point measuring head.

What is a 3-point internal micrometer used for?
It is used to directly measure internal diameters on bores, cylindrical seats and other internal features where an accurate mechanical inspection is required.

How does a 3-point internal micrometer work?
It works through a measuring head with three contacts positioned inside the bore. The measurement value is then read on the instrument thimble.

Why choose an analogue internal micrometer?
Because it offers a traditional mechanical reading, good continuity of use and a direct measuring method appreciated in daily dimensional inspections.

What is the difference between a 3-point internal micrometer and other internal measuring instruments?
The 3-point internal micrometer is specifically designed for direct internal diameter measurement using a dedicated measuring head.

Up to what measuring range is this micrometer available?
The series covers measurements up to 300 mm.

What reading resolution does this micrometer have?
In the smaller ranges the reading is 0.001 mm, while in the larger ranges the reading is 0.005 mm.

What is the ratchet thimble used for?
It helps apply consistent measuring force during inspection, improving repeatability.

Why are carbide contacts important?
Carbide contacts improve wear resistance on the measuring surfaces, especially during frequent use.

Is the setting ring included?
Yes, up to the 100 mm range the micrometer is supplied with a DIN 2250C setting ring. For larger ranges it can be supplied separately on request.

What is the setting ring used for?
It is used for the correct zero adjustment of the instrument before measurement.

What is the extension used for?
The extension increases the measuring depth, allowing easier access to deeper internal areas.

Who is this internal micrometer recommended for?
It is recommended for machine shops, general mechanics, production departments and quality control areas that need to inspect internal diameters with a dedicated instrument.

What are the most common mistakes when using a 3-point internal micrometer?
Common mistakes include incorrect zero adjustment, dirty internal surfaces, choosing the wrong measuring range or not properly managing the instrument inside the bore.