Manual of Purpose-Made Woodworking Joinery

Sharpening 151

Setting technique

To set the saw, hold it under your arm, with the

handle in front, the teeth uppermost, and place

the saw- set on the first tooth facing away from the

plunger. Looking down closely from above, squeeze

the saw- set’s levered handle firmly and then carefully

repeat this operation on every other tooth thereaf-

ter from the heel towards yourself and the saw’s toe

at your rear. Then turn the saw around so that the

handle is now at the rear, under your arm, and set the

alternate row of teeth from the toe towards yourself

and the heel – which is gradually worked out from

the under- arm position. The saw is now ready for

sharpening. Note that when setting old saws, squeeze

the levered handle very gently, as the metal becomes

brittle with age and the teeth can snap off in the

setting operation.

SHARPENING

Figure 9.4: This final operation is concerned with

creating sharp- cutting front edges and sharp points to

the outer tips of the teeth, by filing every other gullet

at an angle to the face of the saw on one side – and

then the alternate row of gullets at an opposing angle

to the face of the saw on the other side, as indicated in

the part- plan and elevation in Figure 9.4(b).

Sharpening theory

Figures 9.4(a)(b): The method of sharpening shown

in Figure 9.4(b) is for saws designed to cut across the

grain, such as crosscut- , panel- , tenon- and dovetail-

saws, the theory being that the sharp- pointed outer

tips of the inverted vee- shaped teeth act as knives

cutting two close lines across the timber. Short-

grained pieces of fibre between the lines break up as

the saw moves forward; the broken fibres are col-

lected in the gullets as sawdust and released when the

saw passes through the timber. Rip saws are similarly

sharpened on alternate sides, but the sharpening

angle is square or almost square across the saw, as

indicated in Figure 9.4(a). This eliminates the pointed

outer tips required for crosscutting and produces

square- tipped teeth which provide a scraping/shear-

ing action necessary for effective rip- sawing along the

grain.

Sharpening technique

Figure 9.4(c): When sharpening, take care not to

lose the basic shape of the teeth; this is best achieved

as a saw- set. The idea is that the cut – or kerf – made
by the saw is slightly wider than the thickness of the
saw blade, to create clearance and facilitate an easy
sawing action. However, too much set can be a disad-
vantage, as the saw tends to run adrift in an oversize
saw kerf. For this reason, it is advisable to set the saw
slightly less than the numbered setting indicated on
the saw- set and only reset the saw when it is really
necessary – not every time the saw is re- sharpened.

Saw- set tool

Figures 9.3(a)(b): As illustrated, the saw- set has a
knurled hand- screw controlling a wheel- shaped,
bevelled anvil – the edge of which is numbered with
different settings, relative to points- per- 25mm – pp25
or ppi (points- per- inch) – and not teeth per 25mm
(which is always one less than pp25 and if used, there-
fore, creates more set). The anvil has to be adjusted so
that the required pp25 numeral (6 pp25 setting shown
in Figure 3(b)’s plan view) is exactly opposite the
small plunger which ejects when the levered handle is
squeezed.

Set

78 77 76

79

Plunger

78

80

7 6

81

76

Part

Plan

Part

To e Elevation

(a)

(b)

Figure 9.3 (a) The saw- set positioned over the saw’s
teeth; and (b) Part end- and front- elevation of the alternate,
numbered settings and part plan- view of the saw- set in its
77th setting- position.