IMPORTANT PLEASE READ - Due to a high workload of booked metal casting courses and sign commissions any orders placed during 16th to 21st of August inclusive will be on hold

You can still checkout, and we will process orders, dependent upon stock levels when we re-open on the next working day. Thank You!

Apologies for any inconvenience caused

Used Stock to Clear- FREE postage

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.