At a is the front and at b the back bearing, affording journal bearing to a hollow spindle c, which carries the shell d of the work-gripping chuck, the clutch ring h and a collar i, in which is pivoted, at j, the clutch levers g. This collar is threaded upon c and is locked in position by a ring lock nut j′. The clutch arm k slides upon a rod x, and has a feather projecting into a spline in x. The core e of the work-gripping chuck is fast upon the inner spindle f, which revolves with the outer one c. The left-hand end of f abuts against the short arms of the clutch levers g, and it is obvious that when k is operated back and forth upon x, it moves the clutch h endways upon c, and the cone upon h operates the levers g, causing them to move the inner spindle f endways and the inner cone e of the chuck to open or close. Suppose, for example, that k (and hence h) is moved to the right, and the long ends of g will be released and may close moving their short ends away from the end of f, and therefore releasing e from its grip upon the work. In moving k to the right the sleeve l is also moved to the right, and its serrations at l′ being engaged with the tongue p, the sleeve m is pulled forward. Now the bar or rod of which the work is made is held at one end by the chuck, it is supported by the bushing z in the end of spindle c, and in the bushing s in the arm of sleeve m, while it has fast upon it a collar t. When therefore m is pulled forward or to the right, its arm meets t and pulls the rod or bar for the work through the chuck e.
On the other hand when k and therefore h, l, and m, are moved to the left, levers g are opened at their long ends by the cone of h. The short ends of g push the inner spindle f to the right, e passes through d, and being split, closes upon the work and grips it, the parts occupying the positions shown in the [figure]. The same motion of k passes l through the sleeve m (the teeth at n raise the catch p, allowing l′ to pass through m) so that at the next movement of k to the right, m will be pulled a second step forward, again passing the work through the chuck. q is merely a pin wherewith to lift p and enable m to be moved back, when putting in a new rod for the work; k is operated by a link from u to v, the handle for moving this link being shown at w in the [general view].
To prevent the sleeve m from moving back with l it is provided with a shoe o, pressed by the spring r against x, thus producing a friction between m and x that holds m while l slides through it. r′ is to regulate the tension of the spring at r. y is merely a sleeve to protect the clutch mechanism from dust, &c.
Box tools for screw machines are used for a great variety of special work. They are simply boxes or heads carrying tools and a work-steadying rest.
Fig. 714.
[Fig. 714] represents a box tool for a screw machine. The cylindrical stem fits into the turret holes and contains a steadying piece or rest g to support the work and keep it to its cut. In the box tool shown in the figure, there are four cutting tools set in to the depth of cut by the screws a, b, c, and d respectively, and a fifth for rounding off the end of the work is shown at e.
