Granite surface plates are made from igneous rock that has undergone intense natural formation processes. This rock is composed primarily of quartz, feldspar, and mica, and features a tightly packed crystalline structure that delivers outstanding hardness and long-term stability. The flat structure and uniform grain make granite a preferred material for high-precision platforms used in industrial inspection.
The composition of granite typically includes 40–60% feldspar and 20–40% quartz, with trace amounts of black minerals contributing to its distinct color. High-quality granite tends to have finer grains, bright feldspar luster, and strong internal density-making it an excellent base for measuring equipment.
Granite contains a high level of silicon dioxide (SiO₂), classifying it as an acidic rock. While some types may contain trace levels of natural radioactivity, these are generally unsuitable for indoor use. That said, due to its low water absorption, high compressive strength, and excellent chemical resistance, granite is ideal for outdoor applications and demanding environments.
Key Features of Granite:
Dense and Durable:
Granite has low porosity (0.3%–0.7%) and low water absorption (typically 0.15%–0.46%). It exhibits excellent compressive strength, often ranging from 100 MPa to over 300 MPa, especially in fine-grained types.
Hard Surface:
With a Mohs hardness of around 6 and a density between 2.63 to 2.75 g/cm³, granite resists scratching and maintains its shape under stress.
Stable for Long-Term Use:
The low thermal expansion coefficient and chemical resistance allow granite plates to stay precise even in fluctuating environments.
Excellent Machinability:
Granite can be processed into a variety of sizes and shapes, and its surfaces are often polished to a mirror-like finish. It's also highly resistant to weathering-ideal for outdoor use.
Maintenance of Granite Surface Plates (Also Referred to as Marble Surface Plates)
Although granite is exceptionally hard and stable, routine maintenance is key to ensuring long-term precision. Over time, especially with frequent use, surface flatness can degrade, affecting the accuracy of measurements. When this happens, either on-site reconditioning or factory servicing may be required.
Steps for Granite Surface Plate Maintenance:
Inspect Surface Accuracy
Use a calibrated gauge or straightedge to check current flatness and identify any wear or deviations.
Rough Grinding (if needed)
If there are deep surface scratches or pits, a rough grinding process is carried out to remove them and restore flatness.
Semi-Fine Grinding
This step helps further smooth the surface, eliminating fine scratches and ensuring the platform meets standard tolerances.
Fine Polishing
Final surface finishing is done using abrasive materials to achieve high-precision flatness suitable for metrology applications.
Post-Maintenance Verification
After resurfacing, the platform should undergo flatness certification and rechecking after a stabilization period.
Conclusion
Granite surface plates are an investment in accuracy, durability, and low maintenance. With proper care-including periodic inspection and resurfacing-they can serve as reliable reference tools in quality control labs, workshops, and manufacturing facilities for many years without compromising measurement results.