93 



| inch in thickness at the hub and f inch in thickness at the rim. 

 The width of the arms at the web should be If inches and at the 

 rim 1| inches exclusive of the connecting curves at web and rim 

 Six pieces 10^ inches long, 2f inches wide, and inch in thickness, 

 must be carefully fitted as shown in Fig. 174. 



After fitting, the connecting joints are glue sized, and when 

 dry carefully scraped smooth with a sharp chisel, and a saw kerf 

 ins- inch deep cut in each. The tongues used for tenons in these 

 kerfs should be a little 

 less than H inch long, 

 the grain of the wood 

 running always at right 

 angles to the line of the 

 joint to give the greatest 

 strength to the tenons. 



The six pieces should 

 be glued in two groups 

 of three pieces each; 

 and when dry, these two 

 groups can easily be 

 refitted, if necessary, 

 and glued. 



The next step is to draw, from the center formed by the inter- 

 section of the six pieces, a circle 5 inches in diameter, representing 

 the web of the arms, and, near the extremities of the pieces, the 

 arcs of a circle 20| inches in diameter, representing ^ inch greatei 

 diameter than the outside diameter of the rim. Carefully divide 

 these last arcs into six equal spaces with the dividers, bringing 

 the points thus obtained as nearly to the middle of the six arms as 

 possible; and from the six points thus spaced, draw radial lines con- 

 necting them with the center or intersection of the six arms. 

 These radial lines (she ^n dotted in the drawing) will be the center 

 line of each arm. 



Saw off the ends of the arms on the above 20f -inch arcs, and 

 from the center again draw on the six arm-pieces a third circle, 

 whose diameter should be at least | inch less than the inside diam- 

 eter of the rim, in this case 19 inches. On these arcs measure 

 f inch on each side of the center line, and on the circle represent- 



