bore 38 of the housing 36 through an end cap 52 the end cap 52 is attached to the end 44 of the housing 36 by means of bolts 54 and includes a sleeve bearing 56 engaging the cylindrical surface of the rod 19 the attachment of the plunger 48 to the rod 19 is by means of the bearing assembly 50 which includes tapered roller bearings 58 held in place on the rod 19 by a lock nut 59 with the assembly 50 being attached by screws 60 to a flange 61 of the plunger 48 at its opposite end the plunger 48 is located in the bore 38 and reciprocates in a cylindrical sleeve 62 attached to a radially inwardly extending lip 64 of the housing 36 by means of screws 66 the plunger assembly 46 is rotatable on the rod 19 about the longitudinal axis 17 of the apparatus on the tapered bearings 58 and the housing 36 is likewise rotatable on the rod 19 at the sleeve bearing 56 a helical spring 68 is positioned in the bore 38 about the plunger 48 and extends between the flange 61 and the lip 64 on advance of the plunger 48 toward the female member 16 the spring 68 interposed between the flange 61 and the lip 64 causes the male member 14 to advance into engagement with the female member 16 to close the chuck the spring 68 holds the chuck members together in the chuck closed position the spring 68 is compressed on the further advance of.