Item RR20 - Unusual Shrinkage Rule. 6-foot length.
my experience this is a very uncommon shrinkage rule. Apparently factory made,
but unmarked, this maple rule is 72 ¾ inches long and is graduated (only on one
side) in 1 quarters of an inch, with 6 successive 12 inch courses, marked in
feet with red circles at 12 inch intervals. The ends have brass tips, with
copper rivets. On the back side “E.B. Broome” is stamped twice (probably an
owner), and a single large, hand stamped “3/4 SHRINK” is stamped midway along
the length. Actually, t “3/4“ refers to the total ¾ inch shrinkage that the
rule calculates over the complete 6-foot span of the rule. The usual shrinkage
calculation of the common smaller (12 to 24 inch) shrink rules is per foot.
This longer rule conforms to the common 1/8” shrinkage per foot—the value that
is used to compensate for the shrinkage of molten cast or malleable iron when it
cools. This uncommon rule, then appears to suit the calculation of shrinkage
during the production of quite large iron castings. It is clearly an oddity for
a shrink rule collection. The gradations and numerals on this rule are clearly
readable. It has dings and dirt from use. Easily Good.
Price - $55.00