890 THE YOUNG FARMER'S MANUAL. 



FIG. 154. 



SHAPE OF TUB EDGE OF A JACK-PLANE IRON. 



as circular on the edge, from corner to corner, as the figure. 

 Place the try-square against one of the edges of the iron, to see 

 if one corner is not being ground off too much, as shown by the 

 dotted line. If a jack-plane iron is ground straight on the edge, 

 as shown by the dotted line, it will cut a shaving so wide that 

 the plane will choke or clog. The edge should be ground on as 

 true a circle as is practicable, from corner to corner, and if the 

 basil should be found upon trial to be too thin for planing hard 

 and knotty stuff, let it be ground a little more blunt. 



572. Fig. 155 shows the correct form for the jointer and 

 smoothing-plane irons. The edge, from corner to corner, should 

 be ground convex but little. If it is ground very true, and the 

 middle is about one-thirtieth of an inch more prominent than the 



