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Special Tools Solve Tricky Problems for Missouri Manufacturer

Sedalia, Missouri - Quality Question: how to measure a part 80" long to a close tolerance of .002"? This was the challenge at Gardner Denver Machinery Inc., which had long searched in vain for a reliable way to check the external length of an impeller used in a blower it produces and the case in which it fits, requiring an equally tight tolerance.

"We had looked for any available instrument to perform this function and asked several manufacturers until we learned from attending the IMTS show that there was a universal gage available that possibly could get us to our 80" requirement," says Ray Tyler, Quality Assurance Engineer at Gardner Denver, the well-known producer of compressors and blowers, pumps and oil field drilling equipment.

Fowler Solution

At the show, Tyler reports, he saw a Fowler/Bowers internal/external universal gage that normally measures to 10". After presenting his impeller measuring problem to the Fred V. Fowler Company, it was suggested that two 40" extensions could be added to the gage to do the job. The gage was designed to accept extensions which are standard "off the shelf" components. However, 80" had never been requested.

After a demonstration at Gardner Denver's facility by Fowler, using a single extension to measure 40", it was determined that the gage should be accurate for the 80" measurement if it is preset to a master the same way it is to be used on Gardner Denver's components. Later it was proven that the universal gage did repeat within .00015" over 80".

"It was the first time we had needed to measure any length beyond 66" and it was clearly an unusually difficult assignment," he said. Tyler reports that a key part of measuring 80" was to employ two machine operators to hold the extended gage's ends against the part, using the constant measuring force of the gage which has a range of .625". Tyler adds that this constant measuring force nullifies deviations often caused by different operators of the instrument.

The Bowers universal gages have minimum/maximum/TIR modes, a resolution of .00005"(.001mm), a rotating display as well as two features not yet employed by Gardner Denver: direct RS232 output and two presets. "We also use certain accessories, especially the spherical contact points, depending on whether we measure flat or curved surfaces," he says. Normally the standard Bowers gages designed for Fowler are used to measure inside and outside diameters, threads, slots, recesses, grooves, tapers and similar aspects of parts.


The company, which received its ISO 9001 certification in 1995, spends a good deal of time in training its operators to use various types of metrology equipment. "We believe in careful training so that production operators can solve their own problems. It's also highly-time efficient."

Use of this instrument may not be confined to the long impeller and its case, according to Tyler. "It will actually be used for anything that needs quick inside and outside diameter measurements.