Fig. 637.
Fig. 638.
When the tailblock of a lathe fits between the edges of the shears, instead of upon raised Vs, it is sometimes the practice to give them a slight taper fitting accurately a corresponding taper on the edges of the shears. This enables the obtenance of a very good fit between the surfaces, giving an increased area of contact, because the surfaces can be filed on their bearing marks to fit them together; but this taper is apt to cause the tailstock to fit so tightly between the shears as to render it difficult to move it along them, and in any event the friction is apt to cause the fit to be destroyed from the wear. An excellent method of obviating these difficulties is by the employment of rollers, such as shown at r in [Figs. 637] and [638], which represent the tailstock of the Putnam Tool Company’s lathe. In some cases such rollers are carried on eccentric shafts so that they may be operated to lift the tailstock from the bed when moving it.
Fig. 639.
A very ready method of securing or releasing a small tailstock to a lathe shears is shown applied to a wood turner’s hand rest in [Fig. 639], in which a a represents the lathe shears, b the hand rest, c the fastening bolt, d a piece hinged at each end and having through its centre a hole to receive the fastening bolt, and a counter-sink or recess to receive the nut and prevent it unscrewing. e represents a hinged plate, and f a lever, having a cam at its pivoted end. A slot for the fastening bolt to pass through is provided in the plate e. In this arrangement a very moderate amount of force applied to bring up the cam lever will cause the plate d to be pressed down, carrying with it the nut, and binding the tailstock or the tool rest, as the case may be, with sufficient force for a small lathe.