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Surface Plates – The Types, Use, and Calibration


Surface plates provide a flat plane used as a horizontal reference point for your dimensional measurements. They can be made from granite, metal, cast iron, or glass. Granite is considered to be the best material for a surface plate due to its surface hardness, low thermal expansion, no rust or corrosion, little warping, and long wear life attributes. These attributes result in very accurate, stable and precise measurements.


Serving as the baseline for all measurements, surface plates play a vital role in quality control. The surface is required to be extremely flat with accuracy up to 0.00001 inches or 250 nm for grade AA or AAA plates. Surface plates often check and zero out other pieces of equipment, so accurate and precise measurements are imperative. Machine shops, automotive and aerospace manufacturers require tight tolerances for shop tools and use surface plates to asses for warped areas on manufactured parts.

Surface plates must be calibrated on a regular basis, at the very least once a year, but we recommend every six months. Though granite is the ideal surface, abrasive dust or repeated sliding of gages can create wear spots that are invisible to the naked eye. Problems most commonly occur at areas with frequent use, so frequent calibration will ensure chipping, warping or wear has not occurred. An uneven surface will impact the functionality of the whole plate causing error in measurements and the passing of defected parts.


To maintain quality, contact Grand Rapids Metrology. GRM is a premier provider of surface plate calibration. We can assist you in ensuring its accuracy for use in your processes.


Contact Us! 800.348.5701

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