OF
A PUNCH MACHINE,
For Engravers to Calico Printers.
The usual method of making Punches for engraving Copper Cylinders, (otherwise than by the milling system) is to cut the desired pattern on a die, and then to transfer that pattern by blows or pressure to the punch, from which it is again transferred to the cylinder. My Machine in this operation, unites motion to the needful pressure; and thus renders the result more easy and complete. This effect I could the better ensure, because the surfaces of my punches are essentially convex, or rather cylindrical; as will appear when my engraving Machine comes to be described. Their convexity however, can be diminished at pleasure—whence this Machine is capable of offering useful assistance to a maker of flat punches.
In [Plate 23], A B [fig. 1 and 2], is the body of the Machine, with the vibrating bar C D laid upon it; reposing especially on the correct and level parts of the body at a b; this bar contains the die c, with which it vibrates between the cheeks B R, as impelled by the screws E F, it’s centre of motion being the pin P, duly supported by the strong shoulder A. In a line with the bar C D, is placed a second vibrator G, containing the steel d, that is to become a punch, already rounded into the cylindrical shape it must have when finished. This vibrator has it’s centre of motion at e [fig. 1], and it need not be added that the curvature of the punch depends on it’s distance e d from that centre: for the centre of the long bar C D is so distant as to have little influence on it’s formation. Further, the cap or bridge H I, which furnishes a centre for the smaller vibrator G, can be brought forward to any useful position by the nuts K L: that cap sliding horizontally between the cheeks M N as directed by the small arms m n. This motion, then, taken from the nuts K L, serves to impress the work of the die on the steel prepared for the punch; and this being done to a first degree, both the handles O Q, are laid hold of: and by turning the screws the same way one of them goes forward and the other recedes, until the punch and die have been in contact over half their surface. At this moment both screws are turned backward, and the motions of the two vibrators reversed: by the repetition of which alternate motions accompanied by the needful pressure, the whole pattern is transferred from the die to the punch—when the latter is taken out of the Machine, and filed up in the usual method.
It should be observed, that the smaller vibrator G can be displaced with ease when the nuts K L are withdrawn: and this should be frequently done to examine the progress of the impression. Nor is there any difficulty in re-entering the figures. In a word, the perfection of this process depends more on much motion than on violent pressure: whence this facility of re-entering is a desirable property. This Machine is usually laid on a bench or tressel, with a long mortice in it, into which the feather x of this Machine enters so as to be firmly fixed.