Concentricity is generally reserved for high-precision parts, and only when there is a need to control median points. An example of concentricity is shown in Figure 1. In the top section, the concentricity symbol is applied to the axis of the part. The boxed symbols can be read "relative to datum A, all median points of opposing elements on this cylindrical surface must lie within a cylindrical tolerance zone of 0.5 in.? The lower section shows a part that meets this requirement. The side view of the part shows the median points for each surface element and the end view shows the cylindrical tolerance zone. The end view also shows a possible surface that meets the size limits of the part.
Verifying concentricity is a time-consuming process, and in many cases it is recommended to use runout or position tolerance in lieu of concentricity. Johnson Gage (Bloomfield, CT) has introduced the affordably priced ?Centrax? Runout and Concentricity Inspection System for verification of cylindrical runout or concentricity in manufacturing or inspection applications. The new JCR-1 model incorporates precision datum rolls, a unique upper tension roll assembly, and integral axial stop pins to assure proper part staging and absolute gage accuracy.
To accommodate both part specific and universal applications, the unit features an infinitely adjustable indicator mounting arm with fine-adjustment positioning and a variable CMM tee-slot mounting stand. It is equipped with a belt-drive to remove operator influence and simplify operation while increasing gage reliability and repeatability. Typical applications for this system include finished and semi-finished fasteners and fittings, screw machine products, and high-precision medical parts.
Additional features include: system accuracy less than two microns, adjustable from 0.125 in through 1.0000 in, available with standard Mitutoyo Test Indicators or Digital Test with SPC output, standard adjustable articulated indicator mounting arm and tee-slot mounting for infinite positioning options. The system also features adjustable axial stops to simplify part positioning and prevent motion during inspection. Easy-to-
read permanent etched scales on the mounting stand simplify repeat measurement applications. The unit can be used on optical comparators or other measurement systems with an optional fixture base. The JCR-1 can also be used for adjustable or part-dedicated configurations. The standard ?Centrax? JCR-1 model is priced at $995.00.
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The Johnson Gage Company, 534 Cottage Grove Road, Bloomfield, CT 06002, 800-245-4243, www.johnsongage.com.
