The above causes may result in imperfect cutting when the machine is in good order. When the machine is not in the proper condition, and the knife is dull, or of a shape not adapted to the work, accurate cutting cannot be expected.
When piling up sheets see that each sheet is laid in exact register with all the others, that is, that the printed pages, guide marks, and edges are all in the same position throughout the pile. One sheet on top laid the wrong way may be the cause of cutting every other sheet of the pile wrong unless (and this is very important) the operator looks at the under sheets to make sure that they are all laid alike.
When cutting or trimming printed sheets it is necessary that the operator should jog the sheets to the pressman's feed edges. These should be marked plainly, without chance of misunderstanding. If they are not, he should ask for directions. One wrong cut will spoil the whole pile.
When a sheet is taken off a pile for examination or for any other purpose, care should be observed that it is laid back again uniform with the other sheets. A pile is easily disturbed in this manner either when swinging it over, turning it around, or rejogging, if the utmost care and orderliness are not observed.
Papers received from the mills or from dealers are not always trimmed squarely, but have what is called a mill edge. This edge is only approximately straight and the corners only apparently square. For accurate work, either in printing or in cutting, one or two edges may need to be retrimmed on a paper cutter to get them straight and have a true corner. The ultimate accuracy of the finished work will depend upon this proper trimming before the sheets are printed.
Exact register and accurate trimming can be secured only by working from the same edges of the paper at every operation and the edges must be straight and squarely cut. When the edges are thus trimmed they should be marked with a red crayon, or in some similar manner, in order to be readily identified at each handling.
A pile may be tested for squareness by jogging it in the cutter table against both the back gage and the side gage, if the machine gages are themselves in perfect adjustment. If it is difficult to see whether the sides of the pile are close against the gages at all points, narrow strips of paper put between the pile and gages will show whether the pile touches the gages uniformly.
When cutting lithographed work or similar close-register printing, where large sheets are apt to come with an irregular edge, a small wooden block against the back gage or the side gage at points on the sheet where the original register guides of the press were placed, will usually insure cutting on an accurate line with the printing. In this manner the same points of contact as were used in the press feeding may be secured.
To cut a pile of paper in half, fold over the top sheet and fold at the middle, carefully matching the edges. Crease this fold distinctly and use the crease as a guide when the sheet is opened out and laid on the pile. To cut into thirds or fifths it is better to measure the sheet exactly with a rule and make clear pencil marks at the points of cutting.
Hand-made papers have rough, uneven edges which are thicker than the rest of the sheet and, therefore, require particular care in jogging and clamping. They should be handled in small piles.