Precision Inside Micrometer Set 50-1500mm – 0.01mm Resolution with Calibration Ring & Carbide Tips

Description

I. In-Depth Product Analysis

Measuring large internal diameters accurately in heavy engineering applications—such as pipe interiors, large engine cylinders, and bearing housings—requires a tool that offers both structural stability and extended reach. Our H-301 Series Precision Inside Micrometer Set is the definitive solution for these demanding tasks. It combines a precision 0.01mm resolution micrometer head with a comprehensive set of modular Φ15.5mm steel extension rods.

The modular design is the cornerstone of this kit's flexibility. Instead of purchasing a separate micrometer for every internal size, this single set allows operators to measure from 50mm all the way up to 1500mm by securely screwing together different combinations of extension rods (ranging from 13mm to 300mm in length). The Φ15.5mm steel tubing provides a crucial balance of weight and strength, significantly reducing the natural deflection and bowing that occur when using thinner, longer rods in large bores, thereby preserving measurement accuracy at extreme lengths.

For long-term industrial use, the measuring contacts are tipped with hardened carbide . This upgrade dramatically extends the lifespan of the instrument, resisting abrasive wear when repeatedly measuring rough cast iron, steel pipes, and heavy machined surfaces. The included precision calibration ring is essential for metrological traceability; it provides a certified physical master standard, allowing technicians to instantly zero the micrometer head and guarantee the absolute accuracy of every subsequent measurement.

II. Technical Specifications

The H-301 series offers a wide variety of modular sets, allowing you to select the exact maximum measuring capability needed for your specific production line.

Core Specifications:

• Resolution: 0.01mm

• Accuracy Formula: (3 + n + L/50) μm (Where * n * = number of extension rods used, L = maximum measurement length in mm).

• Extension Rod Diameter: Φ15.5mm steel tubing.

• Contact Points: Hardened carbide-tipped for extreme wear resistance.

III. FAQ (Frequently Asked Questions)

Q1: How is the 50-1500mm measuring range achieved with this single set?
A: This is a fully modular system. The set includes a precision micrometer head (which has a 13mm travel, covering the 50-63mm range) and multiple extension rods of varying lengths. By securely screwing the correct combination of rods onto the micrometer head, you can reach any precise length within the specified range. The extension rods are designed to be perfectly interchanged for quick set-up changes.

Q2: Why are carbide-tipped contact points necessary for internal measurements?
A: Carbide (tungsten carbide) is exceptionally hard and resists abrasive wear. In industrial environments, you are often measuring rougher materials like cast iron, uncoated steel, or abrasive metal pipes. Standard steel contacts will wear down over time, leading to inaccurate readings and the need for expensive recalibration. Carbide tips maintain their precise spherical shape for millions of measurement cycles, preserving long-term accuracy.

Q3: What does the accuracy formula (3 + n + L/50) μm mean in practice?
A: This formula mathematically guarantees the maximum permissible error of the set based on your configuration. "n" is the total number of extension rods you connect, and "L" is the total measurement length in mm. For example, if you assemble 4 rods to measure a 600mm bore, the maximum potential error is (3 + 4 + 600/50) μm = 19 μm (0.019mm). This ensures reliable compliance with strict engineering tolerances.

Q4: What is the advantage of the Φ15.5mm steel extension rod diameter?
A: When measuring large bores, the length of the extension rod makes it susceptible to sagging and deflection under gravity. Thinner rods (such as 10mm or 12mm) will bend enough to cause significant measurement errors, especially at lengths over 500mm. The Φ15.5mm diameter provides superior rigidity, preventing bending and guaranteeing that the reading truly reflects the internal diameter of the bore rather than a distorted, wobbly rod.

Q5: How do I maintain the precision of the extension rods?
A: The extension rods are precision-ground to exact lengths and feature fine threads for connection. Keep the threads clean and lightly oiled to prevent rust and seizing. Always align the rods straight before screwing them together to avoid cross-threading. Store them back in the designated slots of the wooden case immediately after use to prevent bending or dropping.

IV. Applications & Industry Uses

• Heavy Machinery Manufacturing: Measuring large bored holes in industrial machinery frames, presses, and gear boxes.

• Engine Cylinder & Block Inspection: Checking the internal diameters of large marine engines, diesel generators, and heavy equipment cylinders.

• Pipe & Pressure Vessel Testing: Verifying the internal dimensions of large-diameter pipes, flanges, and pressure tanks in the oil and gas industry.

• Bearing Housing & Gear Inspection: Precise measurement of internal bores for large industrial bearings, main shaft housings, and gear components.

• Aerospace & Automotive Heavy Components: Internal verification of large structural tubes and heavy cast alloy parts in specialized vehicles.

• Quality Control & Metrology Labs: A standard reference tool for verifying master setting rings and large custom fixtures.

V. Accuracy & Working Principle (Accuracy & Mechanics)

The H-301 series achieves its 0.01mm resolution through a combined micrometer screw and modular rod system. The micrometer head operates on the classic screw-and-nut principle: a precisely threaded spindle with a 0.5mm pitch advances linearly as the thimble rotates. With 50 divisions on the thimble, the device offers a 0.01mm resolution . To measure large bores, the operator assembles multiple Φ15.5mm extension rods to the head until the assembly is slightly smaller than the target internal diameter. The remaining gap is then closed using the fine adjustment of the micrometer head. The final measured diameter is calculated by adding the physical lengths of the extension rods used to the precise reading on the micrometer thimble.

VI. Calibration & Maintenance

1. Zero Setting with Calibration Ring: Before commencing production measurements, install the micrometer head onto the base extension rod. Gently insert the measuring contacts into the included precision calibration ring . While slowly turning the thimble, feel for the light contact point against the ring's internal wall. Lock the spindle and verify the reading matches the engraved diameter of the ring.

2. Clean the Measuring Faces: After each use, wipe the carbide-tipped contact points and the anvil with a soft, dry cloth. The presence of oil, metal chips, or grit on the contacts is the leading cause of measurement drift.

3. Proper Storage: The wooden case with foam inserts is designed to securely hold every rod. Do not over-stuff or force components. Dropping the rods can distort their straightness, which will directly cause alignment errors.

4. Annual Professional Calibration: For facilities requiring ISO 9001, IATF 16949, or AS9100 compliance, a full, traceable formal calibration by an accredited metrology lab is required every 12 months .