The complete practical machinist; embracing lathe work, vise work, drills and drilling, taps and dies, hardening and tempering, the making and use of tools, tool grinding, marking by Rose Joshua

Author:Rose, Joshua
Language: eng
Format: epub, pdf
Tags: Machine-tools, Mechanical engineering
Publisher: London, Low
Published: 1895-03-25T05:00:00+00:00

should have one end cut square for a wrench to fit, and in the other end a hole, tapped clear down to its bottom and fitting the thread of the stud loosely ; the stud will then bottom in it when being screwed in, while, when the stui is home in the cylinder, the tool will leave it easily witli out unscrewing it again.

SCRAPED SURFACES.

Tliere are many who believe that surfaces properly planed are sufficiently true for all ordinary practical purposes ; but if those persons were to apply a surface plate to a well-planed surface a foot square, or to a common connecting rod, key and gib, as they usually leave the planer, they would be effectually cured of the fallacy of their opinion upon this matter.

It is impossible to hold a piece of work sufficiently firm that it can be cut by a machine tool without springing it; and though in stout work having a fair bedding beneath the clamping bolts, and in work in which the pressure referred to is sustained in a direction to directly compress the metal of the work, the amount of this spring may be almost imperceptible, still, in light and in a great deal of other work, the amount of spring due to the pressure of holding the work is sufficiently great to throw it out of true. Another of the reasons for the necessity of using surface plates is, that all work alters its form from having its surface skin removed, as will be hereafter explained. All working flat surfaces should be surfaced to a surface plate, whether they are intended to be finished with a file or a scraper. Scrapers are not intended for use as tools to take off a quantity of metal, but for the purpose of making the work very true, being used by itself or in conjunction with a file to ease away the high spots; not because it is impossible with a file of even sweep and flat cross surface to file ti'ue, but because it is a quicker and easier method of obtaining a flat surface, and one that is absolutely indis-

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