The Hempel quoin of iron
296
properly wedged with quoins.
Wood
is
cheapest
and most used, but it necessarily receives hard treatment and is soon worn out. Its liability to warp is another objection. For newspaper forms and book-work the metal side-stick is preferred. Quoins are the blunt wedges of maple, hickory, or boxwood that are forced against the side-stick by means of shooting-stick and mallet. Quoins
and side-sticks of wood shrink after they have been wet and dried, and gradually relax their pressure this sometimes causes a piing of the form. To pre;
vent this accident, as well as to put a stronger pressure on the type, iron quoins, commonly known as patent quoins, have been invented. They are
made
styles, and some are protected by The iron quoin most approved of is in two pieces, each having two small inclined planes of equal length, with cogs or teeth on the interior
in
many
patents.
sides.
A
key-wrench, that grips the interior cogs or teeth, expands the
two pieces
to a wider parallel
The Hempel quoin.
and gradu-
ally tightens the type in the form.
A tongue on one half of the quoin, fitting in a corresponding groove in the other half, prevents either half from being
twisted out of line.
by this wrench
is
The power that can be exerted
greater than that usually obtained