An excellent example of special chuck is shown in [Fig. 853], representing a chuck for holding piston rings. It resembles a face plate screwing on the live spindle at b, and having 8 radial dogs or jaws a, let into the face d, and secured thereto, when adjusted by the bolts and nuts e. A mandrel is fast in the centre of the chuck carrying the cone c, upon which rest the cone surfaces on the ends of the dogs a, so that screwing up c, by means of the nut shown, throws the dogs a outwards, causing them to grip the inside of the piston ring as shown in the face view of the chuck.
Fig. 854.
In [Fig. 854] is shown Swazey’s expanding chuck. b is the body of the chuck driven on an arbor a. The hub of b is turned taper to receive a disc c, which is split partly through in three places, and wholly through at z. By means of the nut and washer d e, the disc is forced up the taper hub and caused to expand in diameter and grip the bore of the work, or ring r, the face of b serving to set the face of the ring against to hold it true sideways.
The chucks employed by wood workers for driving work without, the aid of the back or dead centre of the lathe are as follows:— On account of the fast speed at which the wood-workers’ lathe revolves, it would be undesirable to have their chucks of iron, because of the time it would take the lathe to start them to full speed, and also to stop them after shifting the belt from the driving to the loose pulley of the countershaft, and further because of the damage the tool edges would receive if they accidentally came into contact with the face of the chuck. For these reasons wood workers’ chucks are usually built up upon small iron face plates.
Fig. 855.
[Fig. 855] represents a cement chuck, consisting of a disc of hard wood a, screwed firmly to the face plate b; at c is a round steel point located at the axis of the chuck.