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.
[Ill.u.s.tration: Fig. 13 ELECTRIC MOTOR OVERHEAD, BELT DRIVE]
The chain drive is like the direct-geared except that it subst.i.tutes a chain and two sprockets for two gears.
It is not generally understood what a large amount of power is required to drive a paper-cutting machine, and how important it is that the number of working parts connecting the belt pulley to the knife be as simple and few as possible in order to eliminate friction and lost motion, and to secure efficiency. Every cut costs money for the power consumed.
[Ill.u.s.tration: Fig. 14 ELECTRIC MOTOR UNDERNEATH, GEARED DRIVE]
An inch-high pile of writing paper with a sharp knife may take one thousand pounds for each foot of length of the knife to drive it through. A higher pile on a fifty-inch power cutter may take three tons pressure, plus the automatic clamping effort and plus frictional losses, and (more important) plus a tremendous increase in case the knife is dull.
_Care of the Machine_
A man is known by the condition of the machine he keeps. Keep the knife sharp. That is the first rule to repeat every day and every hour of the day. The second rule is to oil every hole and place required on the machine. The third rule is to keep the machine and its neighborhood scrupulously clean. The fourth rule is to learn by heart and follow the printed directions attached to the machine by the maker. If you do not understand or if you cannot follow correctly every instruction on the printed instructions attached to the machine by the maker, first ask your foreman or superintendent. If the directions are not clear, write, or ask the office to write, to the maker for a detailed explanation or to have his traveling representative come and explain them. Any operator who does not understand the adjustments of the machine he operates has but partly learned his trade. Be particular to see that the driving pulley on your machine runs at the speed given for it on the manufacturer"s directions.
Keep the machine always in adjustment. See that the brake band is adjusted so that when the starting lever is thrown in to start, the friction is entirely released and there is no drag on machine.
Do not allow the knife to sink any deeper into the cutting stick than to sever the last sheet of the pile.
Never use more pressure on the clamp than is necessary to hold the pile without drawing or slipping; any additional pressure is only an added strain on the machine.
Jog your stock before putting it in the machine and do not use the back gage for that purpose. Continual hard jogging with heavy lifts of stock against first one end of gage and then the other will quickly knock it out of square or loosen it.
A little talc.u.m powder, French chalk, or powdered boracic acid dusted on the table makes the stock handle easier.
A slip-sheet of paper or thin pulp board placed on top or on the bottom of the pile, and cut up with it, protects delicate surfaces from finger marks or soiling. Keep your hands and ap.r.o.n clean. Keep the machine clean in every part.
Use only wrenches furnished with the machine, because they fit the bolt heads properly and because they are the correct lengths to put on the proper tension.
Do not use a monkey wrench, because, unless the jaws are carefully adjusted, it will destroy the bolt heads and if used on small bolts, on account of its length and power, is apt to strip the threads or break the bolt or part.
Occasionally go over every part of machine and see that all taper pins, bolts, nuts, etc., are snug in place.
A locked cupboard or box at the cutting machine is useful to keep the full set of wrenches provided, clean waste, colored crayons, a good magnifying gla.s.s, powdered pumice stone, French chalk, talc.u.m powder, boracic acid, special cutting pads, and boards for making them, size strips, dimension records, etc. The oil can should stand always filled and ready on its bracket.
If a belt is put on too tight, it may pull so hard on the bearings as to heat and cause them to cut. It is easier not to put the belt on too tight at first and to relace it several times while it is stretching, than it is to repair a rough bearing.
Keep clean waste in a box. Destroy dirty, oily waste instantly after use, or place it carefully inside a fireproof oily waste can if provided. Do not put dirty, oily waste away or leave it around. It is most dangerous and many plants have been burned by its spontaneous combustion.
Have a definite fixed time to oil, and to clean the machine. Mark the hours when to oil every day, and the day and hour when to clean and polish the machine every week, on the maker"s direction sheet attached to the machine.
Oil with intelligence, not just with an oil can and oil. Oil freely, but not sloppily. Oil should not drip upon the floor. Oil should not flow over parts not requiring it. An excess of oil on a brake band will prevent its acting and stopping the machine promptly. Wipe out the excess oil in this case by pa.s.sing a rag under and around the bands.
Oil that runs or drops or is wiped off is wasted.
Oil the parts above the table carefully and thoroughly. A few drops of oil on the palm of the hand and applied to the four front and back faces of the knife-bar prevents dripping on the table from the oil can.
Run the machine through a few strokes after oiling and then wipe off clean with a cloth or piece of waste the surfaces against which the stock to be cut is placed.
When oiling, remember it is only the oil that reaches the bearing that does any good. Any surplus that runs over and defaces the machine is waste.
The best kind of oil to use is a free-running, light-colored petroleum machine oil. Cheap oils cost more in the end.
_Operating the Machine_
The character of the cutting depends upon, first, the machine, second, the knife, and third, the man.
Successful cutting is a fine manual art. The finest razor improperly stropped and used in unskilled hands does poor work. The finest cutting machine unintelligently operated will stultify the best efforts of the printing plant.
The machine that has the simplest mechanism evolved by long experience and study ensures the first safeguard of accuracy. The knife that fulfils the specifications given elsewhere furnishes the second. And third, the man whose standard of work is high, who is conscientious in following his instructions, who is big enough and broad enough to understand how important his position is, and how necessary, therefore, it is for him to cooperate with every other department in a friendly and intelligent manner, completes the tripod that can stand up successfully under any job.
A cutting machine is a sharp-edged tool and, therefore, dangerous when run by a careless or unskilled operator. "Look before you leap"
applies especially to the cutting machine. Its action is powerful and quick. Accidents occur through failure of the operator to watch his own motions and because of the improper operation of the machine through failure of some of its parts. Sufficient safety devices to make all accidents impossible would render the cutting machine as useless as an axe in a velvet case. Accidents which occur from undue wear or neglect to oil are apt to happen. Two preventives are available: _first_, to train the operator to care; _second_, to provide as many safeguards as can be utilized and still permit commercially successful operation.
With the modern high-speed machine operating at from twenty-five to forty cuts a minute, the time consumed in the cutting room is not the time taken by the knife to pa.s.s through the stock, but rather the time getting the stock laid up and measured ready to cut. Consequently, these latter operations are the ones to study for savings.
The time and labor required to cut a job depends upon the number and kind of motions of the hands and body and feet that are made to get the stock ready and to take it away. The fewer motions necessary to do this and to operate the machine, the easier and pleasanter it is to work at a cutting machine.
Powdered chalk and naphtha put on the bright parts and nickel and allowed to stay over night will polish off in the morning and leave the machine appearing clean and free from rust.
The clamp strap ways should be kept clean and free from the fuzz from the cuttings and thick oil. This can be done by occasionally cleaning them out with kerosene.
If the oil gets in the friction brake band the machine may not stop promptly at the proper point. Throw off the driving belt, and throw on the starting lever to loosen the brake band; then pa.s.s a rag around under the band, between it and the clutch rings, so as to remove the oil, then throw off the starting lever. If a piece of waste is laid on the lower part of the friction brake band just next to the ring, it will keep it free from oil for some time.
Rub the knife and other bright parts of the machine with an oily rag every night. This will prevent the rust forming with the variation of temperature between day and night.
When using the graduations on its rim to measure by, always keep turning the gage screw wheel in one direction, without reversing it, when pulling the back gage forward for successive cuts. This will keep up all the slack and lost motion of the screw and its nut. If the screw wheel is moved first one way and then another, little dependence can be placed upon the graduated reading of the scale.