US Patent: 177,884
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| Improvement in metal-turning lathes
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Patentee:
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| Salmon W. Putnam, Jr. (exact or similar names) - Fitchburg, Worcester County, MA |
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Patent Dates:
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| Applied: |
Sep. 03, 1874 |
| Granted: |
May 23, 1876 |
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Joel Havens
"Vintage Machinery" entry for Putnam Machine Co.
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Description: |
| A. H. Evans & Co. - patent attorneys
In practice mechanics experience greater or less difficulty in making taps, dies, and screws to agree in their pitch or lead. This is often the case when taps are chased in a lathe, and afterward hardened and tempered, as there is always more or less variation occasioned by shrinkage or expansion and a hole threaded with a tap made under such circumstances will not agree with a screw which has not undergone a like process, or which is made from a different material, although cut in the same machine. In many cases it is necessary to cut screws in lathes aside from that in which the tap was made, but the same imperfections, will generally be found, and often in a larger degree; and again it is frequently required to cut the same screw or screws in several lathes, and as the leading-screws of all lathes seldom agree, and are rarely perfect, their imperfections are readily comprehended even when the machines are new, and when worn their defects increased. These mechanical defects are of universal existence, but more plainly met with on large taps and screws, and particularly those with square and United States standard threads. As a partial remedy, screws with V-threads are generally cut smaller in diameter than should be, to fit properly, while in other cases these defective points are of such magnitude as to necessitate the imperfect and impracticable method of expanding or contracting the leading-screws of lathes, &c., by the application of heat or cold. To overcome these defects, and at the same time have other advantages, is the object of my invention, which consists in a mechanism for actuating the tool-carriage at a greater or lesser speed than-that given by the leading-screw, and in an improved tapering attachment, as will be hereinafter more fully set forth.
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