Fig. 47.
The plough knife for mill-boards should not be ground at too acute an angle, or the edge will most likely break away at the first cut. The shape shown at [fig. 47] is suitable. The knife should be very frequently ground, as it soon gets blunt, which adds greatly to the labour of cutting.
After an edge has been cut, each side should be well rubbed with a folder to smooth down any burr left by the plough knife. Then a piece of common paper with one edge cut straight is pasted on to one side of the board, with the straight edge exactly up to the cut edge of the board. Then a piece of paper large enough to cover both sides of the board is pasted round it, and well rubbed down at the cut edge. After having been lined, the boards are nipped in the press to ensure that the lining paper shall stick. They are stood up to dry, with the doubly lined side outwards. The double paper is intended to warp the board slightly to that side, to compensate for the pull of the leather when the book is covered. If the board is a double one, a single lining paper will be sufficient, the thinner board helping to draw the thicker. The paste for lining boards must be fairly thin, and very well beaten up so as to be free from lumps. It is of the utmost importance that the lining papers should stick properly, for unless they stick, no subsequent covering of leather or paper can be made to lie flat.
When the lined boards are quite dry, they should be paired with the doubly lined sides together, and the top back corner marked to correspond with the marks on the top back corners of the book. Then near the top edge, with the aid of a carpenter’s square, two points are marked in a line at right angles to the cut edge. The pair of boards is then knocked up to the back and lowered into the press as before, so that the plough knife will exactly cut through the points. The same operation is repeated on the two remaining uncut edges. In marking out those for the fore-edge, the measurement is taken with a pair of compasses ([fig. 48]) from the joint of the book to the fore-edge of the first section. If the book has been trimmed, or is to remain uncut, a little more must be allowed for the “squares,” and if it is to be cut in the plough, it must be now decided how much is to be cut off, remembering that it is much better to have the boards a little too large, and so have to reduce them after the book is cut, than to have them too small, and either be obliged to get out a new pair of boards, or unduly cut down the book.
Fig. 48.