The following is excerpted from “The Essential Woodworker,” by Robert Wearing. In our opinion, “The Essential Woodworker” is one of the best books on hand-tool usage written in the post-Charles Hayward era. Wearing was classically trained in England as a woodworker and embraced both power and hand tools in his shop and in his teaching.
The mortices should be cut before sawing the tenons, as the latter are more liable to suffer accidental damage before assembly. It is not good practice to grip the work in the vice because then it cannot be tested for verticality, and if it is driven down in the vice during the process, it can become scored. Instead, cramp the work to a morticing block (Fig 106a) with G-cramps or handscrews. The block can be gripped in the vice (Fig 106b) or bolted to the bench (Fig 106c). This method is particularly useful when the bench has a front apron which prevents cramping. The morticing block is useful when the workpiece is small and thin.
Fig 107a shows how a shallow trench can be cut before beginning the mortice proper. Simply lean on the chisel until there is a crunch, then wipe the chisel across (Fig 107b) removing the small chips. The chisel can now be positioned without effort. Before starting to chop, put a depth mark on the chisel (a piece of masking tape will do). If two mortices are to be cut (Fig 108), two depth marks are required (Fig 109). Do not cut the first mortice to full depth or the second will be chopped over a hole and the inside corner may break away (Fig 110). The first mortice should be chopped to a reduced depth (Fig 111) then the second to full depth, thus avoiding this risk.
Having cramped the work securely to the block, drive in the chisel near one end of the mortice, bevel towards the centre (Fig 112). Check that it is vertical by placing a small straightedge against the true face (Fig 113); a longer rule will foul the handle. Withdraw the chisel, turn it round and drive in again with the bevel towards the hole. Push forward to break off the chip, then lever it out. Continue the sequence of drive in (Fig 114), break off the chip (Fig 115) then lever out (Fig 116). Continue almost to the end of the mortice, leaving a small piece of waste on which to lever. Frequently check that the chisel is vertical. Reverse the chisel and proceed to the other end. Continue the method, backwards and forwards until full depth has been reached (Fig 117). Finally chop down the ends at the knife marks, break off and remove the chip without bruising the ends.
Accuracy of depth can be tested by using an adjustable depth gauge or an improvized wooden one (Fig 118). If there is a haunch socket, this is chopped in the same way, right to the end of the component as in Fig 108. The mortice cannot be narrower than the width of the chisel, so it follows that any whittling of the sides of the mortice to neaten it will make it oversize. Keep the chisel vertical and do not permit it to twist as this will also result in an oversize mortice. The practice of first drilling a row of holes and then opening them up neither saves time nor produces a more accurate mortice.