Modern sheet-metal workers' instructor : practical geometry, mensuration, properties of metals and alloys ... by Rose Joseph H

Author:Rose, Joseph H
Language: eng
Format: epub
Tags: Sheet-metal work
Publisher: Chicago, Ill. : Drake
Published: 1906-03-25T05:00:00+00:00

be made red hot, and then pickled for twenty-four hours in slightly diluted muriatic acid, and immediately on being removed should again be completely immersed for about two hours in a solution of chloride of zinc. If the casting cannot be made red hot, it should be immersed for about ten minutes in dilute sulphuric acid and warmed to about 90 degrees Fahrenheit, then pickled in muriatic acid for two days, and afterwards allowed to soak for two hours in a mixture of chloride of zinc solution and salammoniac, about two ounces of the latter to a gallon of spirits.

The casting, by whichever method cleaned, is now ready to be dipped gradually into the tinning pot. Should it not be sufficiently tinned the first time, the surface should be well rubbed with a piece of cork directly the casting is withdrawn from the melted tin, and be again dipped in the chloride of zinc solution and then once more into the tinning pot. Sometimes it is required to tin a part of a casting and to use the copper-bit. When such is the case it is essential that the surface be cleaned and smoothed by scraping or otherwise, then soaked with raw spirits of salts, and then with chloride of zinc solution in which salammoniac has been dissolved. Then the tin should be applied by means of the copper-bit, and a piece of cork used to rub in the tin where there is a difficulty to get it to adhere. Tinning in this way, though not so strong as tinning in the way just described, is sufficiently effective for most purposes.

PRACTICAL PROBLEMS IN SHEET-METAL WORK.

To describe a pattern for a square tapering article.

The plan aiul vertical liei^dit or elevation are shown in Fifif. 147. Draw the diagonals and take the distance from the center a to b, and mark off the same from g to d. Take the distance from a to 1 or k, and mark off the same from h to e. Draw a line through the points d, e, to cut the perpendicular line at f* Then draw the perpendicular line af, Fig. 148, and take the radius fd, Fig. 147. and with it

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