Item RR20 - Unusual Shrinkage Rule.  6-foot length. 

In 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

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