Screw-plate.
A steel plate having a series of holes of varying sizes, with worms and notches for cutting threads.
It is usual to bore a smaller hole on each side of that in which the screw is cut, and connect them with the latter by a slit, forming angular cutting-edges, which remove the metal, as shown at
a b c,
Fig. 4739. The wire is commonly held by a hand-vise in the left hand, and the plate operated with the right hand, several holes, of gradually diminishing diameter, being employed to produce the desired thread.
In some cases, for very short and small threads the holes are merely threaded, and not notched, as shown at
d.
e is a folding device formerly employed for cutting screw-threads; the larger holes are near the joint, so to allow greater holding power.
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Screw-plates. |
For screws exceeding 1/16 inch diameter, it is customary to use a die-stock with movable dies; several arrangements have been adopted in these for holding and adjusting the dies; in
f the edges of the dies have triangular notches sliding on corresponding ribs in the opening of the stock, and are held by one of the handles when screwed in. The lower figure has a pin on each side, which in one position fits a semicylindrical groove in the die, so as to hold it; when rotated half round, it presents a plain side to the die, permitting its removal.
