L28 



1>. \TTKKX MAKING 



Only straight-grained wood should be used for teeth. The 

 segments for building up the rim should be cut out next, then the 

 arms put together and shaped as required. It is a good plan to 

 fasten the arms central to the fare plate of the lathe, and to turn 

 out a recess, say -jV inch or - ; ;\, inch deep to receive the hubs as 

 shown in Fig. 238. This makes a stronger connection and does 

 away with the trouble of fittiiig and connecting the hub. with the 

 thin feather edge of the hub fillet, to the surface of the web of the 



Fig. 238. 



arms. The same method is of great advantage when fitting the 

 hubs of pulleys and other wheels. The arms must be put together, 

 with inserted tongues in the joints, as illustrated and described in 

 Fig. 169; arid if they are to be worked to an elliptical section, it is 

 easier to do this before fixing them in the wheel. At A, Fig. l^! s . 

 the construction of the arms is shown, and at B the core prints, 

 hubs and arms, with the manner of connecting these parts. 



After building up enough courses of segments to equal half 

 the width of the rim plus half the thickness of the arms, the inside 

 only of this part of the rim is turned out to the required shape, 

 including the central rib a Fig. 239, which must be of a thickness 

 just equal to the thickness of the ends of the arms. The recesses to 



