Many of the standard bench-lathe chucks on the market present the disadvantage of having a very short gripping surface. It is also difficult at times to release the work from the draw-in chuck without tapping on ihe hand wheel. When the rear end of the collet has a larger hole than the front, the work is also constantly tossing about. The accompanying engraving shows the construction of a lathe chuck which is designed to remedy these troubles. This chuck was especially built to hold drill rods from 3/16 to 5/8 inch in diameter. The body is made of tool steel. The taper shank should first be fitted to the lathe in which the chuck is to be used, so that the latter may be inserted in the spindle and finished. The nut A is made of machine steel and casehardentd. It may be turned with a spanner wrench, holes being provided as shown. Collets of the required size are made of tool steel and hardened. The rear end of the collets have holes of the same size as the front, so as to prevent the work from being tossed about. A spring is inserted in the body of the chuck, which is held in position by a Hanged collar B, which in turn is retained by dowel pins. When the collet is in position, it is forced against the collar and spring by nut A. When this nut is released, the spring forces the collet out and thus releases the work, which can be removed without trouble. These collets should be tempered so that the center is as soft as possible, to prevent their being easily broken. As will be seen by referring to the illustration, this chuck can be made in almost any shop without the use of special tools.

Fig. 142 - An improved lathe chuck with spring-actuated collet.