The standards carrying the cross slide are segments of a circle struck from the centre of the driving drum, which is necessary to enable the raising and lowering of the cross slide, and maintain a uniform tension on the belt driving the emery wheel without employing an idler wheel or belt tightener.
Fig. 2019.
[Fig. 2019] represents Wm. Sellers & Co.’s drill-grinding machine, in which the drill is held in a chuck operated by the hand wheel a. The jaws of the chuck grip the drill at the outer corners of the cutting edge as shown in [Fig. 2020], and so as to grind the point of the drill central to those corners. In order to give to the cutting edges a suitable degree of clearance in their lengths, and to allow for the difference in thickness at their points between large and small drills, the following construction is employed.
Fig. 2020.
