Machinery's Reference Series Volume 21-30

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...The same advantages that obtain in the smaller presses, result from the use of the larger ones. There is a saving of time in setting up the tools; there is a possibility of punching small holes in thick stock or of leaving narrow bridges of metal between openings of considerable area; the dies, owing to their accurate and permanent alignment, may be fitted to each other much more closely, produce work that requires less finishing and comes more nearly to dimensions than can be done in any other way. At the same time, the construction effects a great increase in the life of the die, making it unnecessary to grind it anywhere nearly so often as would otherwise be the case. The only disadvantage that can be set off against these advantages is the increased cost, and it appears to be conceded that even with this consideration the balance is strongly. in favor of the sub-press die. Of course the larger sizes of these tools are not made in the familiar circular form illustrated in Fig. 13. Fig. 15 shows three different styles. The one at the rear has the sliding head guided by four vertical posts carefully ground and lapped to fit cast-iron bushings. This is the construction used on heavy work. At the left is shown one in which the plunger is rectangular in shape. This works in a bearing lined with babbitt the same as the cylindrical form shown at the right of the cut and outlined in Fig. 13, although the bearing is not adjustable. The cylindrical form is used for the smaller sizes. The making of a sub-press die requires all the skill of a first-class tool-maker. The method pursued by some, at least, of the men who are engaged in this work at the factory mentioned is about as follows: Taking the dies in Figs. 13 and 14 as examples, the base B and cylinder A are m...