612 



Popular Science Monthly 



Laying Out Angles with a 

 Two-Foot Rule 



T 



'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 



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. 



