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Jamb pegs


#1

G’day; One type of jamb peg I have seen consisted of a piece of
board cut with as many sides as facets required on the gem, at
accurate angles to each other. Thus for eight facets the board would
have eight sides. In the exact centre of the board a hole was bored
which fitted a piece of dowel very tightly, and which had marks along
it’s length, each mark providing a certain angle when the end of the
dowel touched the lapidary wheel with a side resting against the
wheel. The gemstone was preformed to a cylindrical shape by
grinding, and fastened to the end of the dowel with dopping wax. So,
by applying the dopped, preformed stone to the abrasive disc (or flat
surface) a facet would be formed on the stone as each side was
applied, using water as a lubricant. Moving the dowel in or out of
the board provided a different angle. The lapidary surface was
rotated by kicking a heavy flywheel attached to the centre of the
lapidary disc, exactly like an old potter’s wheel used where there is
no electricity. It was possible for very experienced lapidarists to
do surprisingly accurate faceting using this ancient method.

Jamb Peg (2) This was a conical piece of wood with holes drilled
around it. A similar dowel to that in (1) was placed in the
appropriate hole to give the correct angle of grinding.

If you REALLY want to see sketches, mail me direct. – Cheers for
now,

John Burgess; @John_Burgess2 of Mapua Nelson NZ