They can be sharpened by removing a
screw or screws to gain access to the cutting edges for quick,
rapid sharpening. The first type was patented by Hiram Clark on
March 1, 1887 and issued Patent Number 358,731. The first 5
specimens, left to right in the first photo are of this patent
and all are marked on the tang with the patent date.
An assemblage of countersinks that can be
by removing screws that connect their two halves.
The first specimen has two screws
that hold the pivoting two-piece shank together during use.
These two screws have to be removed for splaying the tool for
sharpening. The others have only a single screw for that
This photo shows the two models of the Hiram