Patent Model - Improvement in Collapsible Screw-Taps

Maker and role
James Johnson, Patentee
Andrew Parker, Assignee
Production date
Jan 08 1878
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Object detail

9 x 7 x 3" (22.9 x 17.8 x 7.6cm)
Johnson assigned one-half of his right to Andrew Parker, of the same place. The object of his patent is "to furnish a device by which to collapse the cutting-dies in a screw-thread cutting-tap, so that when the screw-thread has been cut the dies may be closed up to enable the tap to be withdrawn without the necessity of a reverse rotary motion." (Patent Number 198,945)
Object number
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