Straight Edge Inspection Procedures
We Check the Edge Using a Granite Surface Plate as a Reference Our straight edge inspection methods use a certified granite surface plate with traceability to NIST standards. Each straight edge must meet the tolerance specifications as indicated on the print. We check the flatness and straightness for all straight edges as defined below: Flatness - all points on the indicated surface must lie in a single plane within the specified tolerance zone. Flatness is a measure of the difference between the closest point and farthest point from the reference plane. Flatness covers an entire surface and measures the degree to which it approximates a mathematical plane. Straightness - all points on the indicated surface must lie in a straight line within the specified tolerance zone. It measures whether the edge of an object varies from a straight line that extends continuously in the same direction without curving. In addition to flatness and straightness, for units purchased with two qualified edges, we also check parallelism on straight edges as defined below: Parallelism - all points on the indicated surface must line in single plane parallel to the designated datum plane within the specified tolerance zone. Two or more lines or planes, extending in the same direction and everywhere equidistant from each other are parallel to each other if they never meet when projected out into infinity
With the unit fully supported on the surface plate and resting on the qualified edge, we next check for any gaps between the two surfaces using a feeler gauge. This provides a visual indication of flatness and also inspects the tool using a typical set-up for the straight edge during normal fully supported applications.
Other physical dimensions will be checked using indicators, micrometers, or scales as appropriate for the tolerance indicated on the print. Unless otherwise specified, the perpendicularity from the edges to the adjacent sides is not inspected.
		Certification of Inspection Upon completion of the inspection process the certification form is completed. This quality certification document references the serial number on the end of the straight edge to a NIST reference for accountability purposes. For a larger copy of this certificate - click here