Caliper Type Inside Micrometer 5-300mm – Carbide Tips with Ratchet Stop & 0.01mm Resolution

Description

I. In-Depth Product Analysis

When measuring internal dimensions of small bores, undercuts, and internal grooves, traditional three-point internal micrometers or standard Calipers often struggle to access these confined spaces. The H-304 Series Caliper Type Inside Micrometer excels in these exact applications. Unlike rod-type micrometers, this design features two precision-ground, caliper-style jaws that extend outwards, allowing the operator to easily position the measuring points into recessed internal features that are otherwise difficult to reach with standard telescoping gauges or bore gauges.

Built for long-term durability, the measuring jaws across all models are equipped with hardened carbide tips . Carbide offers exceptional wear resistance and maintains its precise geometry even when repeatedly measuring abrasive materials like cast iron or hardened steel, preserving the 0.01mm resolution over countless measurement cycles. The integrated ratchet stop mechanism is another critical feature; it guarantees that a consistent measuring force is applied to the workpiece every single time, eliminating the variable of human hand pressure and ensuring flawless repeatability across batch inspections.

For true measurement traceability, the 5-30mm (H-304-01-000) and 25-50mm (H-304-02-000) models come complete with a standard setting ring . This precision-machined master ring allows the operator to instantly set the instrument to the correct zero baseline by inserting the jaws into the ring. For larger models from 50mm up to 300mm, setting rings and calibration gauges are available as optional accessories to maintain the highest level of metrological integrity.

II. Technical Specifications

The H-304 series offers 12 distinct models, covering the 5-300mm range with precision accuracy varying according to the measuring scale.

Core Specifications:

• Resolution: 0.01mm / 0.001″

• Graduation: 0.01mm

• Measurement Faces: Carbide tips on all models (Stainless steel tips are optional).

• Operation: Ratchet stop mechanism ensures consistent measuring force.

• Setting Rings: Included for 5-30mm and 25-50mm models. (Optional for 50-300mm models).

• Accessories: Spindle lock and zero adjusting wrench included with each unit.

III. FAQ (Frequently Asked Questions)

Q1: What are the primary advantages of a caliper-type inside micrometer over a standard rod-style inside micrometer?
A: The caliper-style design uses two extending jaws rather than a simple point contact or a three-point radial expansion. This unique jaw geometry allows it to easily measure small internal diameters, deep internal grooves, undercuts, and stepped holes where a traditional rod-style micrometer cannot physically reach. It is an invaluable tool for inspecting intricate machined parts and mold cavities.

Q2: Why are setting rings included only for the 5-30mm and 25-50mm models?
A: These two models feature extremely small measuring jaws that rely on very precise dimensional calibration. The included setting ring ensures operators can reliably verify the zero point on these sensitive small-range instruments. For the larger 50-300mm models, the jaw geometry and mechanical leverage require separate setting rings. We offer these setting rings and calibration gauges as optional accessories for medium-to-large range users to maintain full traceable calibration.

Q3: Why is the ratchet stop mechanism essential for this tool?
A: If you tighten the thimble by hand, it is very easy to apply excessive pressure, which will slightly bend the caliper jaws or compress the workpiece, resulting in false undersized readings. The ratchet stop ensures that the exact same, optimal measuring force is applied every single time, ensuring repeatability across different operators and different batches of parts.

Q4: Is the 0.005mm accuracy on the 5-30mm model reliable for precision applications?
A: Absolutely. The 5-30mm model achieves an impressive ±0.005mm accuracy, which is highly reliable for inspecting small precision bores, pneumatic valve bodies, and miniature automotive components. As the measuring range increases (up to 300mm), the allowable error naturally increases slightly due to the longer mechanical leverage of the jaw arms, ranging up to ±0.014mm for the largest models, which remains excellent for general industrial use.

Q5: How do I maintain the carbide measuring tips?
A: The carbide tips are highly resistant to wear, but they should be kept clean. After every use, gently wipe the tips with a soft, lint-free cloth to remove any residual oil or metal chips. Avoid using the micrometer as a "go/no-go" snap gauge by slamming it onto the workpiece; despite the carbide hardness, slamming can cause micro-chipping on the precision-ground points.

IV. Applications & Industry Uses

• Machining & Manufacturing Workshops: Measuring internal grooves, undercuts, small bores, and stepped holes in turned and milled parts.

• Mold & Die Manufacturing: Checking the precise internal dimensions of injection mold cavities, ejector pin holes, and core insert slots.

• Automotive & Aerospace Engineering: Inspecting internal dimensions of small engine valve seats, fuel injector bores, and miniature aircraft components.

• Quality Control & Inspection: A highly reliable tool for verifying critical internal features during incoming inspection and final QA.

• Mechanical Engineering & Maintenance: Assessing internal wear inside small hydraulic cylinders, pump housings, and industrial fittings.

• Precision Instrument Making: Ideal for internal calibration of miniature gauges and precision mechanical assemblies.

V. Accuracy & Working Principle (Accuracy & Mechanics)

The H-304 series achieves its 0.01mm resolution through a highly precise mechanical screw-and-nut system. As the operator turns the friction thimble, an internal threaded spindle rotates and advances linearly. This linear movement pushes a precise wedge or lever mechanism that opens the two caliper measuring jaws symmetrically outward. The distance the jaws open is directly proportional to the advancement of the spindle. The outer sleeve of the micrometer has a 0.5mm pitch thread. By rotating the thimble, the operator observes the 0.01mm graduation marks on the barrel, which represent the linear movement of the spindle and, consequently, the precise internal distance between the two carbide measuring points.

VI. Calibration & Maintenance

1. Daily Zero Check with Setting Ring: Before starting a measurement task, use the included setting ring (for 5-50mm ranges) or an optional calibrated gauge (for larger ranges). Insert the two carbide jaws into the standard ring, gently tighten the ratchet stop, and use the zero adjusting wrench to match the reading on the barrel to the ring's known dimension.

2. Clean the Jaws: The carbide tips must be free of grease, chips, or oil. Wipe them thoroughly with a soft cloth after each use. Grit left on the measuring surfaces will rapidly lead to false readings and can wear down the jaw surfaces.

3. Protect the Precision Threads: Do not force the thimble past the mechanical stop. If the thimble becomes hard to turn, check the locking screw and ensure it is fully loosened. Store the tool in its protective case to prevent accidental drops and thread damage.

4. Annual Professional Calibration: For strict compliance with ISO 9001 or AS9100 quality systems, the instrument must undergo formal traceable calibration by an accredited metrology lab every 12 months .