Fig. 2741.
At w, [Fig. 2735], is a spur for cutting the end grain of the wood in advance of the bit, as is necessary in dado and other across grain work, the construction of the spur is seen more clearly in [Fig. 2738]. The pieces a and b are provided with a recess having four arms or branches, while the spur itself has but three, so that the spur may be set as in [Fig. 2735] and be out of action, or its screw being loosened it may be given a half-turn, so that one of its arms will come below b as at x in [Fig. 2738]. The cutting edges of the spur come exactly flush with the outside faces of a and b, and the bits are so held in their seats that their edges also come flush with these outside faces, which therefore act as guide to the bit; thus [Fig. 2739], shows a beading bit in position, and [Fig. 2740] a section of work finished, a and b being in section. [Fig. 2741] shows a plough in position on the work, a and b being shown in section. It is seen that their inner edges being bevelled, will in using a beading tool, act as a gauge regulating the thickness of shaving taken at each plane stroke, which will equal the depth to which the bit edge projects beyond the bevels of a and b. Similarly in grooving or ploughing the amount to which the bits project below the lowest edges of a and b regulates the thickness of the shaving, and as a and b follow the bit into the work, the blade being once set requires no further attention, the depth gauge regulating the total depth of tool action.
Fig. 2742.
Fig. 2743.
