A granite surface plate is a flat, stable reference surface made from high-quality,
precision-ground granite. It is primarily used in industrial and laboratory environments
for precise measurement and inspection tasks. The stability, durability, and wear
resistance of granite make it an ideal material for surface plates, particularly
for maintaining accuracy over time under heavy use.

Applications of a Granite Surface Plate:

1. Precision Inspection:

   • Surface plates are used as a reference plane for inspecting parts for
     flatness, squareness, parallelism,
     and other geometrical dimensions. Instruments such as dial indicators,
     height gauges, and CMM (Coordinate Measuring Machines)
     are often used in conjunction with a surface plate to measure parts accurately.

2. Layout Work:

   • In manufacturing or machining, granite surface plates are used as the
     base for marking out precise locations on a workpiece, especially for holes,
     cutouts, or assembly points.

3. Calibration:

   • Tools like micrometers, calipers,
     and dial indicators are often calibrated against a granite
     surface plate, ensuring that they are accurate when used for measurement.

4. Precision Assembly:

   • Surface plates serve as a platform for assembling precision components,
     allowing for consistent alignment and the elimination of errors in fit or
     dimension.

5. CMM Base:

   • In coordinate measuring machines (CMMs), granite is often used as the
     base plate because of its dimensional stability, ensuring the CMM performs
     consistently and accurately.

Advantages of Using Granite Surface Plates:

1. Superior Flatness:

   • Granite can be ground and lapped to an incredibly high degree of flatness,
     offering a reference surface that remains consistent over time.

2. Non-reactive:

   • Granite does not rust, corrode, or react chemically with most materials,
     making it ideal for use in various environments, including labs with sensitive
     equipment.

3. Thermal Stability:

   • Granite has a low coefficient of thermal expansion, meaning it doesn’t
     expand or contract significantly with temperature changes, maintaining accuracy
     across different environments.

4. Long Lifespan:

   • Due to its hardness and durability, granite surface plates last for
     many years with minimal wear. They are much more resistant to scratches
     and damage compared to steel plates.

5. Vibration Dampening:

   • Granite naturally absorbs vibrations, which helps ensure more accurate
     measurements by minimizing disturbances when working with sensitive instruments.