Pistol-Grip Three-Point Bore Gauge 6-300mm – Carbide Tips, Calibration Rings & Ambidextrous Design

Description

I. In-Depth Product Analysis

Measuring internal diameters accurately, especially in deep bores or mass-production environments, often requires a tool that is both precise and comfortable to use repeatedly. Our H-305 Series Pistol-Grip Three-Point Bore Gauge is specifically designed to meet this need. It combines the proven accuracy of a three-point self-centering measurement system with a highly ergonomic pistol-grip handle and trigger mechanism.

This unique design allows operators to perform measurements with a single hand. By simply squeezing the trigger, the measuring contacts retract, allowing the gauge to be inserted easily into a bore. Releasing the trigger engages the self-centering three-point contacts against the internal wall, providing a perfectly aligned, repeatable reading on the attached dial indicator. This drastically reduces the manual adjustments required by traditional bore gauges and eliminates operator-induced angle errors.

For exceptional long-term durability, models exceeding 12mm in diameter feature hardened carbide measuring surfaces . These ultra-hard tips resist abrasive wear from continuous contact with cast iron, hardened steel, and rough-machined surfaces, preserving the 0.004mm to 0.007mm accuracy over years of service. Each gauge set includes a matching precision calibration ring for models up to 100mm (optional for larger diameters), allowing you to instantly set a traceable zero baseline. The gauge is also highly adaptable, featuring standard Φ8mm or Φ9.525mm mounting sizes compatible with most industry-standard mechanical or digital dial indicators.

II. Technical Specifications

The H-305 series is available in comprehensive individual units and complete measuring sets.

Individual Units Specifications:

Model Number	Measuring Range	Accuracy	Setting Ring	L	A	Extension Rod
H-305-01-000	6-8mm	0.004mm	Φ6mm	54.5mm	1.5mm	100mm
H-305-02-000	8-10mm	0.004mm	Φ8mm	54.5mm	1.5mm	100mm
H-305-03-000	10-12mm	0.004mm	Φ10mm	54.5mm	1.5mm	100mm
H-305-04-000	12-16mm	0.004mm	Φ16mm	80mm	0.5mm	150mm
H-305-05-000	16-20mm	0.004mm	Φ16mm	80mm	0.5mm	150mm
H-305-06-000	20-25mm	0.004mm	Φ25mm	90mm	0.5mm	150mm
H-305-07-000	25-30mm	0.004mm	Φ25mm	90mm	0.5mm	150mm
H-305-08-000	30-40mm	0.004mm	Φ40mm	97mm	0.5mm	150mm
H-305-09-000	40-50mm	0.005mm	Φ40mm	97mm	0.5mm	150mm
H-305-10-230	50-63mm	0.005mm	Φ62mm	112mm	0.5mm	150mm
H-305-11-230	62-75mm	0.005mm	Φ62mm	112mm	0.5mm	150mm
H-305-12-230	75-88mm	0.005mm	Φ87mm	112mm	0.5mm	150mm
H-305-13-230	87-100mm	0.005mm	Φ87mm	112mm	0.5mm	150mm
H-305-61-000	100-125mm	0.005mm	Φ112.5mm	130mm	0.5mm	150mm
H-305-62-000	125-150mm	0.005mm	Φ137.5mm	130mm	0.5mm	150mm
H-305-63-000	150-175mm	0.005mm	Φ162.5mm	130mm	0.5mm	150mm
H-305-64-000	175-200mm	0.005mm	Φ187.5mm	130mm	0.5mm	150mm
H-305-65-000	200-225mm	0.007mm	Φ212.5mm	130mm	0.5mm	150mm
H-305-66-000	225-250mm	0.007mm	Φ237.5mm	130mm	0.5mm	150mm
H-305-67-000	250-275mm	0.007mm	Φ262.5mm	130mm	0.5mm	150mm
H-305-68-000	275-300mm	0.007mm	Φ287.5mm	130mm	0.5mm	150mm

Complete Sets Specifications:

Model Number	Measurement Range	Set Range	Calibration Rings	Extension Rod	A Dimension
H-305-44-000	6-12mm	6-12mm	Φ6, 8, 10mm	100mm	1.5mm
H-305-46-000	12-20mm	12-20mm	Φ16mm	150mm	0.5mm
H-305-48-000	20-50mm	20-50mm	Φ25, 40mm	150mm	0.5mm
H-305-50-230	50-100mm	50-100mm	Φ62, 87mm	150mm	0.5mm

III. FAQ (Frequently Asked Questions)

Q1: What is the primary advantage of the pistol-grip design over a standard bore gauge?
A: The pistol-grip design allows for true one-handed operation. The operator squeezes the trigger to retract the contacts, inserts the gauge into the bore, and releases the trigger to take a measurement. This dramatically speeds up the measurement cycle, reduces operator fatigue during high-volume inspections, and allows the user to maintain a stable grip on the workpiece with their free hand.

Q2: Why are carbide measuring surfaces only available on models above 12mm?
A: The extreme compactness of the 6-12mm measuring heads leaves very little physical space for three individual mechanical wedges. To maintain the miniature form factor required for these tiny bores, these specific heads are manufactured from specially hardened, ultra-high-grade steel instead of carbide. For all models 12mm and above, hardened carbide measuring faces are standard.

Q3: What calibration rings are included, and what about the larger sizes?
A: A precision calibration ring is included for every gauge up to 100mm. For sets and individual units exceeding 100mm (such as the H-305-61-000 range up to 300mm), calibration rings are available as optional accessories. Because of the massive size of these rings, they are typically ordered separately to ensure cost-effectiveness for users who do not require daily zeroing at those extreme diameters.

Q4: Which dial indicators are compatible with this bore gauge?
A: The gauge head is equipped with a universal mounting mechanism designed to accept standard industrial dial indicators. It supports both Φ8mm and Φ9.525mm (3/8″) mounting stems. You can easily install your preferred mechanical dial indicator or a digital indicator with a digital output for SPC data logging.

Q5: Is this gauge suitable for measuring blind holes?
A: Yes. The three-point contact design is specifically engineered for both blind and through holes. The measuring contacts are positioned close to the bottom edge of the head, allowing you to accurately measure the internal diameter almost down to the bottom of a blind hole where the flat surface ends, without interference.

IV. Applications & Industry Uses

• Automotive Engine & Transmission Manufacturing: Fast, precise measurement of engine cylinder bores, connecting rod ends, and transmission housing internal diameters.

• Aerospace Component Inspection: Reliable verification of hydraulic valve bodies, structural bores, and precision-machined fitting ID's.

• Hydraulic Cylinder Manufacturing: Measuring the internal diameters of deep hydraulic actuator cylinders and pneumatic pressure vessels.

• Precision Machining & CNC Turning: Rapid in-process and final inspection of bored and honed parts on the production floor.

• Quality Control & Inspection Departments: A core instrument for dimensional compliance checks and batch sampling in QC labs.

• Industrial Maintenance & Repair: Assessing internal wear on large pump housings, compressor cylinders, and heavy machinery components.

V. Accuracy & Working Principle (Accuracy & Mechanics)

The H-305 series achieves its 0.004mm to 0.007mm accuracy through a precise mechanical three-point wedge system. When the operator releases the ergonomic trigger, a spring-loaded internal mechanism pushes three symmetrically placed wedges forward simultaneously. These wedges force the measuring contact points to expand outwards at identical rates until they firmly touch the inner wall of the bore. Because the wedges are precision-ground to exact angles, the three contact points automatically self-center the gauge, eliminating off-axis tilting errors. This linear mechanical displacement is transferred up through the shaft to the dial indicator, where it is displayed as a precise dimensional reading. The spring-loaded trigger ensures that the measuring force remains perfectly consistent, guaranteeing excellent repeatability.

VI. Calibration & Maintenance

1. Daily Zero Verification: Before a measurement session, clean the contacts and insert the gauge into the included calibration ring (or optional setting ring for larger ranges). Squeeze and release the trigger to take a reading, and use the SET function or zero ring on your dial indicator to establish the absolute zero baseline.

2. Clean the Contact Points: The small carbide or hardened steel contact points are highly sensitive to debris. After use, gently wipe them with a soft, lint-free cloth. Do not use compressed air, as it can blow dust into the internal wedge mechanism.

3. Maintain the Trigger Mechanism: The trigger is spring-loaded. Keep the trigger area free of grinding swarf and oil buildup. Periodically apply a light drop of instrument-grade oil to the trigger pivot point if it begins to feel stiff.

4. Annual Professional Calibration: For strict ISO 9001 or AS9100 compliance, the complete set (including the indicator) should undergo formal traceable calibration by an accredited metrology lab every 12 months .