Coining-press development is outlined and the author tells how such machinery was adapted to speed-up the production of automobile parts, such as forged arms and levers, by a squeezing process that superseded milling or spot-facing methods. The presses used are very rugged in construction and have the appearance of a plain-type punch-press, except for the knuckle that operates the ram. This knuckle is coupled to a crank by a connecting-rod or link. As the crank revolves, it straightens the knuckle. The pressure transmitted to the ram is many times greater than that which could be produced through a single-acting direct-connected crank-operated type of machine. An additional advantage of the knuckle movement is in the application of pressure at the end of the downward stroke. The position of the ram at the end of the stroke is controlled by a screw-actuated wedge. Different sizes of press are made, ranging in pressure capacity from 100 to 2000 tons per sq. in. of area of the part squeezed.
Details are given of the squeezing operations and the percentages of increase in production over that attained under former methods are summarized. The composition of the dies is specified, and the application of feeding mechanisms to such presses is described.
Grain structure of the coin-pressed forgings was studied exhaustively and photo-micrographs are exhibited. Three specific conclusions were reached and these are stated.
