the back gage without looking down, and a second wheel indicator and pointer permits reading to less than one-thousandth of an inch. Similar indicator ribbons are attachable to the back gage for screw, cable, chain, and metal tape movements.

These indicator ribbons are usually graduated and marked for inches, halves, quarters, eighths, and sixteenths. They are also furnished with metric system measurements, graduated and marked for centimeters and millimeters. They are also furnished extra wide so that both the English inch measurements as well as the metric system measurements may be put upon the same ribbon. When graduated to thirty-seconds of an inch and millimeters a good magnifying glass of about three inches diameter, adjusted in front of the pointer, enables easier and more accurate reading. An easily operated lock for holding the back gage fast to the table at any exact mark prevents variation in the width of cutting.

Fixed distance gage rods and suitable engagements with the back gage are provided for cutting at any time duplicates of exactly the same width, especially valuable for loose-leaf ledger work. Pins and holes drilled in the back gage and table also secure uniform locations impossible to get solely from reading the overhead ribbon or an indicator dial, which latter may be read incorrectly because of poor light or variation in the operator's position or eye.

Locking devices for the back gage ordinarily consist of (a) a friction grip around the moving screw, or (b) about the cable hand wheel, or (c) a clamping device which holds the back gage, or (d), best of all, a fixed grip rod-holding device operated from the front of the table, thus eliminating any possible lost motion through connecting parts from the jogging or chucking of work.

A back gage is split so that different width piles may be cut at the same time, such as trimming the heads, tails, and fronts of books. The fingers at the splits are placed smooth, so that they may be used as side gages to enable the wear of the knife to be taken its full width, instead of just at the usual left-hand end.

Power Back Gage Movement

The larger sizes of cutting machines are equipped with a labor-saving power connection to the main driving shaft which may be thrown in by the operator at will to move the back gage forward or backward by power, a micrometer reading the position to thousandths of an inch.

Special Devices

Special spacing devices for the back gage are revolutionizing many branches of work. The usual screw or cable is relatively slow and undependable and requires care and time to move the work the exact distance required.

The new way is to equip the cutting machine with a back gage operating mechanism having stops which can be set for any width to be cut. The operator simply pulls a lever between the stops, which instantly moves the pile and measures it exactly. Production has been increased six hundred per cent. with such spacing devices.

Gages for measuring the width of the cut may be simply a sample cut the desired width laid upon the pile, or an exact size wood or metal pattern, or the width may be determined by reading on a steel indicator-ribbon attached to the back gage the distance its face is back from the knife edge.

These methods are only approximately accurate, however; for exact cutting, steel distance-pieces of correct lengths to give the different widths of cut required are set against a fixed stop in the back table and the back gage run back until it grips the steel distance-piece. This brings the face of the back gage the desired distance from the knife.

Modern patented spacing devices for the rapid duplication of exact widths in succession, while the machine runs continuously without stopping between cuts, have been perfected so as to enable, on some classes of work, one cutting machine to do the work of six and still obtain accuracy. These spacing devices operate the back gage through a chain or a screw or a gear by means of a lever driven by hand or by power between accurately set stops fixed for any desired width, and thus eliminate the time ordinarily lost measuring the width for each cut.

Among other conveniences on the large modern cutters two starting levers, one at each side of the machine, or a starting bar extending across the front, save several motions at each cut.

A flat piece of metal, called a clamp face, which may be quickly attached to the under side of the fingered clamp, is used to prevent these fingers marking soft or delicate finished stock.

A snake gage is a folding lattice used in front of the back gage of a solid wide face clamp machine to enable the back gage to push the pile up nearer the knife.

For large pamphlets or magazines an extra clamp attached behind the regular clamp to hold the back of the pile down gently by spring pressure will prevent the sheets springing up and away from the back gage, caused by the folds and air between the sheets.

A plate attached to the machine with hooks upon which to hang the wrenches is provided upon the most modern machines and this helps the operator to keep them together and in order.

Guards covering the gearing, knife edge, pulleys, flywheel and other moving parts are required by many state laws, and power cutting machines are, therefore, so designed and furnished complete.

Application of Power

There are five methods of applying power necessary to operate paper cutters: by hand lever, by belt, by direct gearing, by chain and sprocket, and by direct connection of electric motor.

Figure 13 shows an electric motor on a bracket, adjustable vertically, attached to the frame of the cutting machine, driving by a belt from the motor pulley to the machine pulley. The belt cushions the heavy repeated thrusts of the clamp and knife in cutting upon the motor. The electric motor may be set on the floor or on a bracket on the wall.

Figure 14 shows a direct-geared connection of the electric motor through its noiseless rawhide pinion engaging an iron gear on the machine driving shaft. An adjustment is provided for taking up the wear in the gears, in order to maintain the noiseless running of the machine.