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US Patent: 1,547,514
Thread Testing Device
Patentee:
Paul M. Mueller - Hartford, CT

USPTO Classifications:
33/199R

Tool Categories:
metalworking tools : machinist tools : measuring tools : thread gages

Assignees:
Pratt & Whitney Co. - New York, NY

Manufacturer:
Not known to have been produced

Witnesses:
none listed

Patent Dates:
Applied: Nov. 09, 1921
Granted: Jul. 28, 1925

Patent Pictures:
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"Vintage Machinery" entry for Pratt, Whitney & Co.
Description:
Joseph K. Schofield - patent attorney

This invention relates to a thread testing device, and in particular to a device for rapidly determining the accuracy of a number of similar screw threaded members. An object of the present invention is to provide a screw thread testing device which may be adjusted over a wide range of sizes and adapted to quickly compare the accuracy’s of a number of screw threads with a standard screw thread of the same nominal size. Another object of the invention is to provide a device which by substitution of different forms and sizes of screw thread contacting members and by adjustment of the positions of the screw thread contacting members may be used for comparing the dimensions of a number of different types and sizes of screw threads within a wide range. One feature which enables me to accomplish the above objects is that I provide a pair of oppositely disposed screw thread gaging or contacting members having serrated edges corresponding in outline to the particular form of screw threads being examined and, by permitting different sets of contacting members to be readily and quickly substituted, any number of different forms of screw threads may be tested. Another feature which is advantageous is that one of the screw thread contacting members is so mounted that it is adjustable over a wide range to accommodate screw threaded members of varying diameters and the oppositely disposed contacting member is flexibly or resiliently mounted so that it may have a limited movement toward or from the first contacting member. Means are also provided whereby the position of the flexibly mounted contacting member may be determined to a high degree of precision when in screw thread engaging position, so Another object of the invention is to provide contacting members adapted to engage but one thread on either side of the specimen being tested so that the inaccuracy in diameter can be determined independently of any error in the lead or pitch of the screw threads. By the use of both forms of gaging or contacting members upon a specimen and a standard, the error, if any, in lead or pitch can be approximately calculated. It is also an object of the invention to arrange the contacting members and to support the member being tested in such a way that light may be reflected and transmitted through the base of the device so that the contact between the contacting members and cs the screw threaded body may be visually examined, and errors of pitch and angle of sides of the screw threaded body being tested may be readily ascertained. A further object of the invention is to provide a suitable adjustable support for the specimen being tested permitting the specimen to be rapidly placed in operative position relative to the contacting or gaging members. It is also an object of the invention to provide a support suitable not only for plain screw threaded members but for such members as taps in which the gaging members must contact at points on the screw threaded portions near the cutting edges.

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