The frame carrying the emery wheel arbor is fixed to a table d, which is capable of being operated (in a direction across the table a) upon a carriage beneath a. This carriage, or saddle (as it may perhaps be more properly termed), is pivoted so as to allow of its movement and adjustment in a horizontal plane, and since d operates in the slide of the carriage, its line of motion in approaching or receding from the line of centres will be that to which the saddle is set. This enables the grinding of such short cones as the circumferences of bevelled cutters, chamfers, &c., at whatever angle the saddle may be set, however, d may be operated from the feed screw disc and handle f.
The lever handle at the left hand is for operating or rather traversing c by hand; b is a pan to catch the grit and water, the water being led to the back of machine into a pail; c is a back rest to steady the work when it is slight and liable to deflection.
The slot and stops shown upon the edge of c are to regulate the points of termination of the traverse (in the respective directions) of c. A guard is placed over the emery wheel to arrest and collect the water cuttings, &c., which would otherwise fly about.
A large amount of work which has usually been filed in a lathe, can be much more expeditiously and accurately finished by grinding in this machine.
Work to be ground may obviously be held in the same chucks or work-holding appliances as would be required to hold it to turn it with cutting tools, or where a quantity of similar work is to be done special chucks may be made.
Fig. 680.
[Fig. 680] (from The American Machinist) shows a special chuck for grinding the faces of thin discs, such as very thin milling cutters, which could not be held true by their bores alone. The object of the device is to hold the cutter by its bore and then draw it back against the face of the chuck, which, therefore, sets it true on the faces. The construction of the chuck is as follows. The hub screws upon the lathe like an ordinary face plate, and has a slot running diametrically through it. Upon its circumference is a knurled or milled nut c, which is threaded internally to receive the threaded wings of the bush b. A collar behind c holds it in place upon the hub. To admit piece b the front of the chuck is bored out, and after b is inserted and its threaded wings are engaged in the ring nut c a collar is fitted over it and into the counter-bore to prevent b from having end motion unless c is revolved. d is a split bushing that fits into b, its stem fitting the bore of the disc, or cutter to be ground: the enlarged end of d is countersunk to receive the head of the screw e, whose stem passes through d and threads at its end into b, so that when e is screwed up its head expands d and causes it to grip the bore of the disc or cutter to be ground. After e is screwed up the ring nut c is revolved, drawing b within the chuck and therefore bringing the inside face of the disc or cutter against the face of the chuck or face plate, and truing it upon the bushing d. All that is necessary therefore in using the chuck is to employ a bushing of the necessary diameter for the bore of the cutter, insert it in b, then screw up the screw e and then revolve the ring nut c until the work is brought to bear evenly and fair against the face of the chuck, and to insure this it is best not to screw e very tightly up until after the ring nut c has been operated and brought the work up fair against the chuck face.