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Differential Gaging Technique

IP.com Disclosure Number: IPCOM000045899D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hares, K: AUTHOR

Abstract

A technique is described for checking the parallelism of two members that must be maintained parallel to a relatively long planar datum surface within a very small tolerance, such as .00l inch. This normally would require that a slidable checking tool have a tolerance significantly less than the aforementioned close tolerance, such as no more THAN .0001 INCH. TO PROVIDE SUCH A TOOL THAT WOULD HAVE AN ACCURACY OF .0001 INCH DURING TRAVEL OVER A SIGNIFICANT DISTANCE ALONG THE DATUM surface would be very expensive.

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Differential Gaging Technique

A technique is described for checking the parallelism of two members that must be maintained parallel to a relatively long planar datum surface within a very small tolerance, such as .00l inch. This normally would require that a slidable checking tool have a tolerance significantly less than the aforementioned close tolerance, such as no more THAN .0001 INCH. TO PROVIDE SUCH A TOOL THAT WOULD HAVE AN ACCURACY OF .0001 INCH DURING TRAVEL OVER A SIGNIFICANT DISTANCE ALONG THE DATUM surface would be very expensive.

Accuracy of this order can, however, be less expensively achieved by employing a differential gaging technique comprising the following steps: 1 Set up a datum surface parallel to the mounting

surface of the specimen to be measured.

2. Run a first non-contact probe along this datum

surface. (Any runout measured by this probe is

considered to be tool error.)

3. Run a second non-contact probe along the area of

the specimen that is to be measured that is

parallel to the datum surface. (Any runout

measured by this second probe contains both

specimen error plus or minus the tool error.)

4. Electronically add to or subtract from the

specimen runout the signal from the first probe,

thus eliminating tool error and minimizing slide

wear.

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