This is an essential item of equipment where any production work is involved. It is possible in one-off work to manage with a hollow chisel mortising attachment fitted to a drill press, but eventually the advantages of a separate mortiser will become only too apparent.
There are two forms of mortiser: the hollow-chisel type, and the chain mortiser, which works in a similar way to the chain saw. It is chiefly the former which is used in quality craft orientated workshops because it produces the perfect square edge and square bottomed mortises from 1/4 in (6 mm) width up to 1 in (25 mm) or more.
Ill Hollow-chisel mortiser HORIZONTAL BORER
The mortise and tenon joint will always be preferable in quality work to dowelling, but where economy of time is vital, the horizontal borer is an obvious alternative to the mortiser. It usually has two drilling heads side by side and an adjustable table for height.
Figure 112 shows a home-made dowel borer. This was assembled out of engineering scrap with a 1/2. hp (0.373 kW) motor, screw-actuated elevating, and dovetail slide horizontal movement for the working-table taken from an
old milling-machine bought in the local scrapyard. A 1/4 in (6 mm) sliding rod under the table provided an effective distance-stop, and the 1/2in (12.5 mm) capacity Jacob's chuck was mounted direct onto the motor spindle. With the table set at the right height and pushed forward by the pre-set distance against the revolving bit it gave very accurate borings, and such machines, either independent or as accessories coupled to other machines, are invaluable for accurate dowel-work. Minimum safe working distances between machines are shown in Figure 122 and where space is limited the in' or out' feed distance can often be increased by placing the machine in line with a doorway.
Both the mortiser and the horizontal borers have the advantage of operating at very slow speeds and quietly, in contrast to the overhead and portable routers which can be used in some shallow mortising operations.
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