Part II - Lump and Cup Removal
On saws that have been
kinked repeatedly or severely, it’s common to achieve a straight
cutting edge by hammering and tensioning as I described in the
previous installment, but still not have a saw that will cut
This Disston #16’s
cutting edge was hammered straight, but you can see a small bend
remaining in the saw’s back and what appears to be a cup or lump
remaining that will bind in the kerf during sawing and cause the
saw to wander.
A short straightedge
run down the blade allows chalking the lump’s outline on the
concave side. Turn the saw over and transfer the marks to
the convex side of the lump.
Any tension in the
concavity is removed using a small, convex-faced hammer,
hammering on the marks from the outside of the circle inwards.
Each mark represents two light hammer strikes.
Flipping the blade to
the convex side, the lump is hammered out using the large hammer
in exactly the same sequence and locations as in the previous
The blade is checked
again using the straightedge and while there are still lumps and
hollows, they are smaller.
Rub out the old chalk marks and
use the straightedge to make new ones, then repeat the same
marking and hammering sequence of using the light hammer on the
concave side and the heavy hammer on the convex side. Stop
when the straightedge makes full contact with the blade.