Modern Machine-Shop Practice, Volumes I and II

by Joshua Rose

Second, this will render possible a tighter fit than would be possible with a parallel strap and rod.

Third, the width b a being taper, the brasses may be easier made a good fit, because there will be some metal to fit on after they enter at b.

Fourth, the brasses may be made a tighter fit, the bottom brass being tight enough to spring the strap a trifle, easing but not destroying its fit on the rod.

Fifth, the top brass may be made a handsliding fit to the strap without springing the strap open, which being already under a tension because of the spring due to the bottom brass, will be more rigid and permit of a tighter degree of top brass fit, without springing open and away from the rod.

Sixth, this will leave the bottom brass a tight driving fit, and the top a hand sliding fit, which is desirable, because the top brass has to be taken out to get the rod off while the bottom brass remains in its place.

Fig. 2359.

Seventh, what is of more consequence than all, the strap can be more easily and cheaply refitted to repair it. Thus, in [Fig. 2359], suppose the strap to have been closed by pening at d; then whether the end d will be narrowed will depend on the amount the strap was closed, and the amount of taper it had before closing. Let us take, however, the most unfavorable conditions, and suppose that the amount of taper was so small, and the amount of closing by pening so great, that the jaws were made taper and smallest at d. Then the amount to be filed off to bring the width of jaw correct, and a fit to the strap, will be less than if the strap jaws were formed as in [Fig. 2357], as will be seen by comparing [Fig. 2357] with [Fig. 2359], the amount to be filed away being that between the dotted and the full lines in both figures; the amount of closure being the same in the two figures.

But there is another great advantage, inasmuch as in pening, the strap may be pened and tried on the rod, the strap being pened and tried alternately until the required fit is obtained, which is not practicable with upsetting in the blacksmith’s shop.