Granite/Marble V-Blocks: Core Positioning Tool for Precision Centering, Inspection, and Machining of Shaft Parts

Solution Overview

This granite/marble V-block is specifically designed for centering, precision inspection, and machining support of cylindrical and conical parts (precision shafts, bearing inner rings, roller components, pipe fittings). With “micron-level centering accuracy + natural material stability + multi-scenario adaptability” as its core, it addresses three key pain points of traditional metal V-blocks: “centering deviation caused by thermal deformation, rapid wear leading to accuracy degradation, and narrow applicable shaft diameter range”.

Leveraging the ultra-low thermal expansion coefficient (granite: 5-8×10⁻⁶ per ℃; marble: 6-9×10⁻⁶ per ℃), high damping and vibration resistance (vibration attenuation rate ≥ 85%) of high-density granite (Jinan Green/Taishan Green) and high-purity marble, along with precision V-groove machining technology, this V-block achieves a centering error of ≤ 0.002mm for shaft parts and a V-groove angle tolerance of ≤ ±0.01°. It is suitable for positioning micro-shafts (φ5mm) to large shafts (φ800mm), covering scenarios such as precision bearing inspection, automotive crankshaft machining, and wind turbine main shaft calibration. It helps enterprises reduce shaft part positioning errors by 70%, improve inspection efficiency by 50%, and maintain precision for 5-8 years.

Core Function System

1. Micron-Level Precision Centering for Shaft Parts

• High-Precision V-Groove Design: V-groove angles include 90° (for conventional shafts), 60° (for thin shafts/pipe fittings), and 120° (for thick shafts/rollers), with an angle tolerance of ≤ ±0.01°. The surface roughness is Ra ≤ 0.02μm (for granite) and Ra ≤ 0.05μm (for marble). The groove opening adopts arc transition (R0.5-R5mm) to avoid scratching the surface of shaft parts, while ensuring a fitting degree of ≥ 95% with the shaft surface. The centering error is ≤ 0.002mm (for φ50mm shafts), far exceeding that of metal V-blocks (centering error ≥ 0.008mm).
• Wide Shaft Diameter Adaptability: A single V-block can adapt to shaft diameters ranging from φ5mm to φ200mm (conventional specifications). By “combined use” (splicing multiple V-blocks of different specifications), it can cover large shafts from φ5mm to φ800mm. Custom “stepped V-grooves” (a single V-block with 2-3 grooves of different widths) are supported to enable quick switching between multiple specifications of shaft parts without replacing the V-block, reducing tool change time to 30 seconds.
• Centering Stability Guarantee: The V-groove and base are machined integrally (no splicing), with a perpendicularity of ≤ 0.002mm/1000mm between the groove surface and the base bottom. This ensures that the perpendicularity deviation between the shaft axis (after centering) and the machining/inspection datum is ≤ 0.003mm, avoiding the problem of “shaft axis tilt caused by groove surface wear” in metal V-blocks. It is especially suitable for precision shaft roundness inspection and concentricity calibration scenarios.

2. 3D Positioning and Multi-Scenario Adaptability

• Multi-Dimensional Positioning Support: The V-block base integrates a planar datum (flatness grade 00: ≤ 0.003mm/1000mm), which can cooperate with side baffles and pressure plates to realize 3D positioning of shaft parts (centering + axial limit + radial clamping). The base is pre-provided with positioning holes (φ6-φ12mm, tolerance H7), which can be fixed on the tooling platform via positioning pins to achieve collaborative positioning of multiple V-blocks (e.g., segmented support for long shafts). The coaxiality of long shaft positioning is ≤ 0.005mm/2000mm.
• Dual Adaptability for Inspection and Machining: When used as an inspection datum, it can cooperate with roundness testers and dial indicators to inspect the roundness and cylindricity of shaft parts (inspection repeatability error ≤ 0.001mm). When used as machining support, it can withstand cutting vibrations (vibration amplitude ≤ 0.003mm) and is suitable for positioning in lathe and grinder machining of shafts. After machining, the roundness error of shaft parts is reduced from ±0.005mm to ±0.002mm.
• Adaptability Optimization for Special Shafts: For conical parts (e.g., centers, taper shafts), custom “variable-angle V-grooves” (groove angle changes with shaft diameter) are available. For special-shaped shafts with keyways or steps, custom “notched V-grooves” (avoiding protruding structures of shafts) are provided to ensure that centering accuracy is not affected by part structures. It is suitable for positioning over 95% of special-shaped shaft parts.

3. Stability and Durability Guarantee Under All Working Conditions

• Material Deformation Resistance and Vibration Resistance: Granite V-blocks are made of Jinan Green/Taishan Green granite (quartz content ≥ 65%, density ≥ 2.7g/cm³) with a low thermal expansion coefficient. Under a workshop temperature fluctuation of ±5℃, the V-groove angle variation is ≤ 0.001°, and the centering error variation is ≤ 0.0005mm. The high damping property can absorb high-frequency vibrations (50-3000Hz) during inspection/machining, preventing shaft parts from shifting due to vibration and improving inspection data repeatability by 60%.
• Corrosion Resistance and Wear Durability: The V-groove surface is treated with “precision honing + nano-ceramic coating” (coating thickness: 5-8μm), which is resistant to cutting fluids, alcohol, and bearing cleaning agents, avoiding rust and groove surface oxidation issues of metal V-blocks. The surface hardness reaches HS75-80 (for granite), and the wear resistance is 2.5 times that of cast iron V-blocks. After long-term use (≥ 100,000 shaft insertions/extractions), the groove surface wear is ≤ 0.001mm, no regrinding is needed, and the maintenance cycle is extended to more than 2 years.
• Wide Environmental Adaptability: It can be used in humid environments (relative humidity ≤ 90%) and slightly corrosive environments (e.g., semiconductor workshop cleaning agents). An optional anti-static coating (surface resistance: 10⁶-10⁹Ω) is available, suitable for positioning precision shafts in the semiconductor industry (e.g., wafer transfer shafts), avoiding precision impact caused by electrostatic dust adsorption.

Core System Composition

Typical Industry Application Cases

1. Precision Bearing Inner Ring Roundness Inspection: A bearing enterprise uses it for roundness inspection of bearing inner rings (φ30-φ80mm) — adopting a 90° granite V-block (150×100×100mm) with a centering error ≤ 0.002mm. Cooperating with a roundness tester, the inspection repeatability of inner ring roundness error is reduced from ±0.002mm to ±0.0008mm, inspection efficiency is increased from 30 units per hour to 50 units per hour, and the bearing finished product qualification rate is increased by 35%.
2. Automotive Crankshaft Machining Positioning: An automobile enterprise uses it for grinder machining positioning of automotive crankshafts (φ50-φ120mm) — adopting a stepped granite V-block (300×200×150mm, with 2 V-grooves) to adapt to different shaft diameter sections of the crankshaft. The perpendicularity between the V-groove and the base is ≤ 0.002mm/1000mm. After machining, the crankshaft roundness error is reduced from ±0.005mm to ±0.002mm, the main journal coaxiality error is ≤ 0.003mm, and the engine operation noise is reduced by 20%.
3. Wind Turbine Main Shaft Concentricity Calibration: A wind power enterprise uses it for concentricity calibration of 3MW wind turbine main shafts (φ500-φ800mm) — adopting custom 120° granite V-blocks (500×300×300mm, 2 blocks used in combination) to adapt to large shaft diameters. After centering, the straightness of the main shaft axis is ≤ 0.005mm/5000mm, and the calibration error is reduced from ±0.01mm to ±0.003mm. The operation stability of the wind turbine unit is increased by 40%.
4. Semiconductor Wafer Transfer Shaft Positioning: A semiconductor manufacturer uses it for inspection of wafer transfer shafts (φ10-φ20mm) — selecting an anti-static granite V-block (100×60×60mm) with a groove surface Ra ≤ 0.01μm and a centering error ≤ 0.001mm. It avoids electrostatic dust adsorption, and the roundness inspection accuracy of the transfer shaft reaches ±0.0005mm, meeting the requirements of 7nm wafer transfer. The inspection defect rate is reduced by 80%.

Core Competitive Advantages

• Centering Accuracy Far Exceeding Metal: The V-groove angle tolerance of granite/marble V-blocks is ±0.01° (for granite), and the centering error is ≤ 0.002mm — more than 4 times that of metal V-blocks (centering error ≥ 0.008mm). It solves the core pain point of “inspection/machining deviation caused by inaccurate centering” for precision shafts, especially suitable for high-end fields such as aviation and semiconductors.
• Long Precision Retention Period: After 24-36 months of natural aging treatment, 99.5% of internal stress is eliminated. The V-groove wear is ≤ 0.001mm per 100,000 uses, and the precision retention period is 5-8 years (only 1-2 years for metal V-blocks). This reduces frequent calibration downtime and saves over 150 hours of maintenance costs annually.
• Excellent Vibration Resistance and Environmental Adaptability: The high damping property absorbs vibrations to prevent shaft part displacement; the low thermal expansion coefficient ensures precision stability under temperature fluctuations; the corrosion-resistant and anti-static (optional) design adapts to special environments such as humidity, corrosion, and electrostatic sensitivity. The application scenarios are more than twice that of traditional metal V-blocks.
• Extremely Low Maintenance Costs: The nano-coating on the groove surface and the wear resistance of stone eliminate the need for rust prevention and regrinding maintenance required for metal V-blocks (annual maintenance cost of metal V-blocks is about 1,000 yuan, while that of stone V-blocks is only 100 yuan). The integral structure has no splicing gaps, avoiding “precision deviation caused by slag accumulation at splicing joints” of metal V-blocks. Cleaning only requires wiping with a dust-free cloth.
• Strong Customization Adaptability: Customization of angles (60°/90°/120°/special angles), dimensions (adapting to shaft diameters φ5-φ800mm), and functions (anti-static/stepped grooves/notched grooves) is supported, meeting the positioning needs of over 95% of shaft parts. Unlike metal V-blocks that require “one block per shaft”, it reduces procurement costs by 60%.

Full-Dimensional Customization Services

• Basic Parameter Customization:

◦ Angle Customization: Conventional angles 60°/90°/120°, special angles (e.g., 45°/150°) can be designed on demand, with optional angle tolerances of ±0.01°-±0.03°;

◦ Dimension Customization: Length×Width×Height from 80×50×50mm to 800×500×500mm, adapting to shaft diameters φ5-φ800mm. Large V-blocks support splicing (centering error at splicing joints ≤ 0.005mm);

◦ Groove Customization: Single-groove/multi-groove (stepped grooves), groove arc R0.5-R10mm, notched grooves (adapting to shafts with keyways/steps).

• Function and Material Customization:

◦ Function Enhancement: Anti-static coating (surface resistance 10⁶-10⁹Ω, for semiconductor scenarios), nano-wear-resistant coating (for high-frequency use scenarios), ultra-smooth groove surface treatment (Ra ≤ 0.01μm, for optical shaft positioning);

◦ Material Selection: Jinan Green granite (grade 00 accuracy) for ultra-precision scenarios (aviation/semiconductors), marble (grade 0 accuracy) for conventional scenarios, and composite granite (cost-effective) for cost-sensitive scenarios.

• Supporting Service Customization:

◦ Calibration Service: Precision calibration of V-blocks (centering error, angle tolerance inspection), issuance of metrological inspection reports, optional calibration cycles of 1-2 years;

◦ Supporting Solution: Design of an integrated positioning solution (V-block + side baffle + pressure plate) based on the customer’s shaft part drawings, providing trial assembly and verification services;

◦ After-Sales Guarantee: 3-year free warranty for granite V-blocks / 2-year warranty for marble V-blocks, 24-hour response to quality issues, and provision of backup V-blocks to support continuous production.