What Is Two Points Inside Micrometer?

Dec 19, 2025|

product key technologies

01.

Product Definition and Core Positioning

The mechanical two points inside micrometer is a purely mechanical internal dimension measuring tool designed based on the principle of screw micrometer. It focuses on high-precision internal dimension inspection in environments without power supply. Its core function is to measure complex internal dimensions such as inner hole diameter, groove width, stepped hole spacing, and minor diameter of internal threads. It does not require electronic modules and relies on precision mechanical transmission and scale reading. The graduation value is fixed at 0.01mm. It conforms to international/national standards such as ISO 3611-1978 and GB/T 6314-2014. It is an indispensable traditional high-precision measuring tool in machining, workshop quality inspection, metrology calibration and other scenarios.

02.

Core Functions

1. Purely Mechanical High-Precision Internal Dimension Measurement

Basic Internal Dimension Measurement: Covers multiple ranges including 5-30mm, 25-50mm, and 50-75mm, accurately measuring the width/diameter of circular inner holes, rectangular grooves, and square holes with a measurement accuracy of 0.01mm, meeting the needs of both general and high-precision machining (accuracy class 0/1).

Adaptation to Complex Internal Structures: Supports measurement of special internal dimensions such as deep holes (with extension rods), internal grooves, stepped holes, and minor diameters of internal threads. The measuring jaws are made of carbide, adaptable to different workpiece surface shapes (measuring inner holes on arc surfaces, measuring groove widths on flat surfaces).

Auxiliary Geometric Tolerance Inspection: Through multi-directional (3-4 points) layered measurements at different axial depths on the same cross-section, the roundness, cylindricity, and other geometric errors of the workpiece's inner holes can be indirectly determined.

2. Guaranteed Mechanical Transmission Precision

Screw Drive System: The two points inside micrometer screw is precision ground with a pitch strictly controlled to 0.5mm and a pitch error ≤0.001mm, ensuring precise conversion between the rotation of the micrometer drum and the linear displacement of the moving measuring jaws.

Constant Force Mechanism: An integrated mechanical ratchet force measuring device automatically slips and emits a "click" sound when the measuring jaws contact the inner wall of the workpiece and reach a preset measuring force of 2-4N. This avoids excessive/insufficient measuring force due to manual operation, ensuring consistency in every measurement.

Mechanical Locking Function: Equipped with a locking nut, the micrometer screw is locked after measurement to prevent displacement, facilitating reading recording and continuous measurement of multiple workpieces.

3. No Power Dependence and Environmental Adaptability

All-Weather Use: Requires no battery power and is unaffected by power outages, low temperatures, strong magnetic fields, etc., making it suitable for workshops, outdoor maintenance, remote factory areas, and other power-free scenarios.

Structural durability: The one-piece forged body is rigid and impact-resistant, with no issues of easily damaged electronic components, and can maintain stable accuracy even after long-term use (service life can reach 5-8 years under normal maintenance).

Measurement Operation

1. Range Selection of two points inside micrometer: Select the appropriate range according to the internal dimension being measured (e.g., select a 5–30 mm range for measuring a 15 mm inner hole, and a 75–100 mm range for measuring a 90 mm inner hole). Over-range measurement is strictly prohibited, as it may deform the micrometer screw.

Equipment Inspection:

Clean measuring surfaces: Wipe the carbide surfaces of the two measuring jaws with a clean, soft cloth or alcohol to remove oil and iron filings, and ensure that there are no scratches or impurities.

Check transmission: Rotate the micrometer drum to check for smooth operation, with no jamming or abnormal noise. After tightening the lock nut, the micrometer drum should not rotate.

2. Zeroing Operation:
Select a standard calibration ring gauge of the corresponding specification (e.g., a 20 mm standard ring gauge for the 5–30 mm range) and clean the inner hole of the ring gauge.
Place the two measuring jaws into the ring gauge and rotate the micrometer drum so that the measuring jaws fit against the inner wall of the ring gauge. Use the ratchet force measuring device to rotate until a "click" sound is heard.

3. Observe the Reading:
If the reading is consistent with the standard value of the ring gauge, no adjustment is required. If the deviation exceeds ±0.002 mm (Grade 0), rotate the internal adjusting screw through the adjusting hole on the side of the micrometer sleeve (for some models) until the reading matches the standard value.