Precision Inside Micrometer Set 150-2100mm – 0.01mm Resolution with Calibration Ring & Optional Carbide Tips

Description

I. In-Depth Product Analysis

When performing internal measurements on large engine cylinders, industrial pipes, and heavy machinery housings, standard Calipers and short-range gauges are inadequate. Our H-312 Series Precision Inside Micrometer Set bridges this gap, offering a comprehensive modular system designed to measure internal diameters from 150mm all the way up to 2100mm with 0.01mm resolution.

The core strength of this kit lies in its high-quality Φ22mm steel extension rods . In long-reach internal measurement, rod deflection under gravity is a primary source of error. The rigid Φ22mm diameter significantly reduces flex and sag, ensuring that the rod assembly remains perfectly aligned with the true geometric axis of the bore throughout the entire measuring process. The interchangeable extension rods (available in lengths of 25mm, 50mm, 100mm, 200mm, and 400mm) can be quickly configured to match virtually any internal dimension within the specified range.

The set includes a precision calibration ring . This machined master standard allows operators to instantly establish an absolute zero baseline, ensuring that every subsequent production measurement is traceable to a certified physical reference. For facilities dealing with rough cast iron, abrasive steel pipes, or high-volume measurement cycles, the optional carbide-tipped measuring faces (Order Model: 312-XX-070) are highly recommended. Carbide provides exceptional hardness and wear resistance, maintaining the perfect spherical geometry of the contact points for years of heavy-duty service.

Technical Specifications:

Dimensional drawing (312-00-060)

II. Technical Specifications

The H-312 series offers multiple kit configurations, allowing you to choose the maximum extension capacity that best suits your production requirements.

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: Φ22mm high-quality steel tubing.

• Included: Precision calibration ring for zero setting.

• Optional Upgrade: Carbide measuring faces (Order Model: 312-XX-070).

III. FAQ (Frequently Asked Questions)

Q1: How is the 150-2100mm measuring range achieved with this kit?
A: The kit uses a fully modular system. A precision micrometer head (which provides the 150-175mm base range) can be combined with various extension rods. By securely screwing together the correct combination of rods (such as 25mm, 50mm, 100mm, 200mm, or 400mm) onto the head, you can achieve any internal measurement length within the 150-2100mm range.

Q2: Why are the Φ22mm steel extension rods important for accuracy?
A: When you extend rods to measure lengths over 1000mm, they become susceptible to bending and bowing under their own weight. This deflection will pull the measuring contacts out of perfect alignment, causing false readings. The thicker Φ22mm diameter provides much greater stiffness than thinner alternatives, ensuring the assembly stays straight and rigid for stable, accurate measurements even at maximum extension.

Q3: What does the accuracy formula (3 + n + L/50) μm mean for this set?
A: This is a mathematical guarantee of the maximum permissible error based on your specific setup. "n" is the total number of extension rods connected, and "L" is the total measurement length in millimeters. For example, if you use 8 rods to measure an 1800mm bore, the maximum potential error is (3 + 8 + 1800/50) μm = 47 μm (0.047mm). This ensures your measurements remain within rigorous engineering tolerances.

Q4: When should I choose the optional carbide measuring faces (312-XX-070)?
A: Standard steel contact points will gradually wear flat when repeatedly measuring abrasive materials like cast iron, rough steel pipes, or sand-cast parts. The optional carbide-tipped upgrade is highly recommended for high-volume industrial production lines, as carbide resists abrasive wear, maintaining the exact spherical contact shape and the 0.01mm accuracy for far longer.

Q5: How do I use the included calibration ring?
A: The calibration ring is a precision-ground master standard with a known exact internal diameter. Before starting a measurement session, assemble the micrometer head and any necessary base rods. Insert the contacts into the calibration ring and gently tighten the thimble until they make contact. Lock the spindle and use the SET function to input the known ring diameter, establishing a perfectly traceable zero baseline for all subsequent measurements.

IV. Applications & Industry Uses

• Machinery Manufacturing & Maintenance: Measuring internal bores in large industrial press frames, gearboxes, and heavy machine tools.

• Engine Cylinder & Block Inspection: Checking the internal diameters of large diesel, marine, and stationary engines during rebuilds and quality control.

• Pipeline & Tubing Manufacturing: Verifying the internal diameter and ovality of large-scale pipes and pressure vessels for oil, gas, and water systems.

• Automotive & Aerospace Components: Inspecting large cast housings, tubular structural elements, and heavy vehicle components.

• Heavy Equipment Fabrication: Critical dimensional verification of large bearing housings, motor casings, and industrial hydraulic cylinders.

• Quality Control Metrology Labs: A primary reference standard for verifying large internal setting rings and custom fixtures.

V. Accuracy & Working Principle (Accuracy & Mechanics)

The H-312 series achieves a 0.01mm resolution through the classic micrometer screw and interchangeable rod principle. The micrometer head features a high-precision threaded spindle with a 0.5mm pitch. Turning the thimble one full revolution moves the spindle exactly 0.5mm; with 50 divisions on the thimble, this yields a 0.01mm reading . To measure large bores, the operator selects and assembles the required Φ22mm steel extension rods to approach the target internal diameter. The final fine gap is closed using the micrometer head's spindle. The total measured internal diameter is calculated by summing the precise, clearly marked lengths of the extension rods used and adding the exact reading on the micrometer head.

VI. Calibration & Maintenance

1. Zero Check with Calibration Ring: Before every measurement task, assemble the base configuration and verify the zero point using the included precision calibration ring . Lock the spindle once the contacts touch the ring's inner wall to establish a traceable baseline.

2. Clean the Threads: The threads connecting the extension rods are precision-ground. Before each assembly, wipe both the male and female threads with a soft cloth to remove any dust, grit, or oil. Cross-threading will permanently damage the precision threads and cause misalignment.

3. Proper Storage: The rods must be stored horizontally in their designated slots within the protective case. Do not store the rods loosely, as they can roll off workbenches and become bent, which will ruin measurement accuracy.

4. Annual Professional Calibration: For strict compliance with ISO 9001, IATF 16949, or AS9100 quality systems, the entire set should be formally calibrated by an accredited metrology laboratory every 12 months .