612
��Popular Science Monthly
��Laying Out Angles with a Two-Foot Rule
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��'HE aver- age car- penter who has any occa- si o n to lay out an angle which does not require absolute accu- racy, such as can be ob- tained with a protract or , can secure fairly accurate^ results with the use of the accompanying table. A standard two-foot rule is required. By opening the rule to different angles we secure corresponding varying openings measured in inches between the edges of the rule, as designated by the letter A,
��The two-foot rule can lay out angles
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��By following this table, an angle of any degree, from the
smallest to the full right angle, can be laid out with
an ordinary carpenter's two-foot folding rule
��Suppose we wish to measure an angle of 20°. By consulting the table for 20°, we find the distance A to be 4 5/32". Using a pair of dividers or an additional rule, spread the two-foot rule apart until the distance A measures 4 5/32 in length. Then the angle B will measure 20°. The table has been computed with- in 1/32", that being sufficient for all practical purposes. — S. H. Samueles.
A Simple Way of Making Facsimile Rubber Stamps
I AY a piece of carbon copying paper ^ face up upon a smooth table. Over this, place a sheet of paper and with a lead pencil write the name. The name will be reproduced on the back of the paper. Lay the carbon papej face down upon a piece of very smooth zinc, and upon this, place the paper on which the name has been written, this also face down. Then with a pencil go over the lines, which now read backwards, thereby tracing the lines upon the zinc. Next, prepare an acid-proof ink by mixing equal parts of py- rogallic acid and sulphate of iron. Go over the lines on the zinc with a pen dipped in this ink. \Mien dry, apply hydro- chloric acid to the face of the zinc. After it has eaten deeply enough, wash off the acid in run- ning water.
A plaster cast is then taken and a reproduction made with rubber in the manner described in the March, 1915, number of Modern Mechanics and the World's Advance. The zinc can also be mounted type-high on a wooden block and used in a printing press.
For those who are not experi- enced in vulcanizing rubber or who do not care to go to the trouble, the following is recom- mended : India rubber, cut up into small pieces, is dissolved in highly rectified spirits of turpen- tine until semi-fluid. This is then poured into the plaster cast, which has been previously dust- ed with powdered graphite.
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