Complete Three-Point Internal Micrometer Set 2-100mm – Carbide Contacts, Calibration Rings & Aluminum Case

Description

I. In-Depth Product Analysis

Purchasing and managing multiple individual bore gauges for different sizes can be costly, disorganized, and inefficient for busy machine shops. Our Complete Three-Point Internal Micrometer Set eliminates this hassle by offering a fully integrated, organized system in one heavy-duty aluminum carrying case. From the ultra-compact 2-3mm head to the robust 50-100mm coated unit, this set guarantees you always have the exact tool needed for the job.

The core of each measuring head lies in its self-centering three-point contact system . Unlike two-point Calipers that are susceptible to off-angle tilting, the three-point design expands three precision-ground contacts outward at an identical, synchronized rate. This mechanically forces the gauge to align perfectly with the true centerline of the bore, eliminating angular errors and delivering highly repeatable measurements of ovality, taper, and true internal diameter.

The set is built with long-term durability in mind. The smaller 2-50mm measuring heads feature a durable, high-quality chrome-plated finish that resists corrosion and scratches, while the larger 50-100mm head utilizes a specialized coated finish to ensure exceptional dimensional stability and resistance to workshop oils. All measuring contacts are tipped with hardened carbide , providing extreme resistance to abrasive wear on rough cast iron, hardened steel, and abrasive alloys. Furthermore, each head comes with its own precision-matched calibration ring , allowing operators to instantly establish an absolute traceable zero point right out of the case, ensuring maximum measurement accuracy from the very first use.

II. Technical Specifications

The complete set is offered in two distinct finishes depending on the measuring range. Each model includes the specified measuring head, matched calibration rings, and extension rods as indicated.

Technical Specifications:

Chrome Plated Finish Sets (2 - 50mm):

Coated Finish Set (50 - 100mm):

III. FAQ (Frequently Asked Questions)

Q1: What is the advantage of the three-point self-centering system?
A: Standard two-point Calipers are prone to tilt inside a bore, resulting in inaccurate off-angle readings. The three-point self-centering system uses three contacts that expand outward at the exact same speed and angle. This mechanically locks the gauge into perfect alignment with the absolute centerline of the bore. It eliminates human positioning errors and guarantees highly repeatable measurements of both the diameter and the bore's overall roundness (ovality).

Q2: How do the included calibration rings work?
A: The calibration rings are precision-ground master standards with exact, known internal diameters (e.g., exactly 25.000mm). Before measuring your parts, you insert the corresponding measuring head into its dedicated ring and use the SET function on the gauge to match the known diameter. This instantly establishes a traceable absolute zero baseline for the entire inspection session.

Q3: Why are carbide measuring faces used on these measuring heads?
A: Carbide (tungsten carbide) is exceptionally hard and highly resistant to abrasive wear. When measuring abrasive materials like cast iron, uncoated steel, or rough-machined aluminum, standard steel faces will gradually wear down and flatten, causing measurement drift. The carbide contacts maintain their precise spherical geometry over millions of contact cycles, ensuring long-term 0.004mm to 0.005mm accuracy.

Q4: What is the difference between the chrome-plated and coated finishes?
A: The chrome-plated finish (used on the 2-50mm heads) provides excellent corrosion and scratch resistance, keeping these smaller, frequently used tools looking and functioning like new. The coated finish on the larger 50-100mm head offers a specialized, durable surface treatment that provides outstanding resistance to workshop oils, chemical coolants, and physical wear, ensuring stability for larger-scale, heavy-duty measurement applications.

Q5: Is this set suitable for use in a high-volume production environment?
A: Yes. The ergonomic design of the heads, combined with the ready-to-use calibration rings and the organized, protective carrying case, makes this set perfect for high-volume quality control, automotive manufacturing, and production-floor inspection. The quick zero-setting and the self-centering design dramatically reduce measurement cycle times.

IV. Applications & Industry Uses

• Precision Machining & Boring: High-precision inspection of bored, honed, and reamed holes in CNC parts.

• Automotive Manufacturing: Measuring engine cylinder bores, valve guide diameters, and transmission housing internal dimensions.

• Aerospace Component Inspection: Verifying the internal diameters of hydraulic fittings, structural tubing, and precision-machined castings.

• Mold & Die Production: Precision checking of core pin holes, ejector bores, and injection mold cavity dimensions.

• Quality Control & Inspection Labs: The definitive reference tool for verifying the internal dimensions of master gauges, setting rings, and fixtures.

• Industrial Maintenance: Assessing the internal wear and ovality of hydraulic cylinders, pumps, and heavy equipment bores during maintenance overhaul.

V. Accuracy & Working Principle (Accuracy & Mechanics)

The H-315/375 series achieves its high accuracy through a precision mechanical wedge system. Inside each measuring head, a high-accuracy threaded spindle pushes three precision-ground wedges forward as the digital thimble is rotated. Because these wedges are machined to identical, exact tolerances, they force the three measuring contacts to expand outward radially at a uniform rate. This synchronized expansion guarantees flawless self-centering. The exact linear displacement of the spindle is measured by a high-resolution digital encoder and displayed directly on the attached indicator. The included calibration rings ensure that this mechanical displacement is mathematically tied to a certified physical master standard, ensuring absolute metrological traceability for every measurement.

VI. Calibration & Maintenance

1. Daily Zero Check with Calibration Rings: Before starting a shift, select the required measuring head and clean its three contact points. Insert it into the included matched calibration ring , gently tighten the thimble, and use the indicator's SET function to match the zero point to the ring's engraved diameter.

2. Clean the Contacts: After every use, gently wipe the three carbide measuring contacts with a soft, lint-free cloth. Any metal chips, oil, or grit left on these precision surfaces will directly impact the measurement accuracy and scratch the workpiece.

3. Protect the Small Heads: The 2-3mm and 3-6mm measuring heads are extremely small and delicate. Handle them with extra care. Always insert them gently into bores and do not force them, as the internal wedges are miniature and very precise.

4. Annual Professional Calibration: For strict compliance with ISO 9001 or AS9100 quality standards, the entire set (including all heads and rings) must undergo a full, traceable calibration by an accredited metrology laboratory every 12 months .