Granite surface plates are inspected and certified using traceable standards in accordance with the current revision of ASME B89.3.7, as well as the previous specification GGG-P-463c. Our inspection and relapping procedure is included in our ISO 17025 scope of accreditation.
Johnson Gage & Inspection, Inc. performs overall flatness accuracy measurement on surface plates using a laser measurement system. Repeat reading is also inspected on each plate we certify, which addresses the ability to reproduce a measurement of a fixed height anywhere on the surface of the plate. These two testing methods together will give you complete information regarding the accuracy of your surface plate.
JGI is able to re-lap surface plates on-site if they are found out of tolerance for a particular grade or requirement. In many cases, resurfacing a plate at your facility and restoring it to a particular grade is more cost-effective than purchasing a new surface plate. Our experienced plate re-lapping technician is equipped to successfully restore the desired accuracy to your plate in a minimal amount of time.
We are an authorized distributor for Precision Granite USA, Inc. We will quote new or reconditioned plates upon request.
To ensure its accuracy, it is recommended to re-test your surface plate when you move it or after a period of heavy-use. Under normal circumstances, well-maintained surface plates are inspected for overall flatness and repeat reading on a yearly basis. You may want to consider changing the calibration interval from annual to six months if your plate undergoes frequent or continuous heavy use, particularly in an environment with moderate to significant particle contamination. If your surface plate is often found out of tolerance at its regularly scheduled recertification inspection, you should consider increasing its calibration frequency to help reduce or eliminate the possibility of errors in your measurements.