**** PLEASE NOTE: The store will be closed from 6th Mar until 10th March 2024 Inclusive. Any orders placed will be fulfilled after that date - subject to stock levels ****

IMPORTANT PLEASE NOTE We are not registered for VAT so the prices you see are the prices you pay!

Please note there is a 4 to 6 week waiting list from placing Tong orders until their dispatch.

Used Stock to Clear  SORRY SOLD OUT

Patternmakers’ contraction allowances

Castings are always smaller in dimensions than the pattern from which they are made, because as the metal cools from its solidification temperature to room temperature, thermal contraction /shrinkage occurs.

Patternmakers allow for this contraction /shrinkage by making patterns larger in dimensions than the required castings by an amount known as the “contraction / shrinkage allowance”. This is done by making use of specially engraved rules, known as “contraction or shrinkage rules”, the dimensions of which incorporated a contraction /shrinkage allowance such as 1 in 75 for aluminium alloys, or 1 in 96 for iron castings.
Due to computer controlled machines being used for pattern-making shrinkage rues are sometimes expressed as a percentage allowance.