Steel Rules with Shrink Graduations Cat. No. EDP Length Width x Thickness Shrink Per Foot Graduation C374-12 51430 12" 1 x 3/64" 1/10" 4R – 8ths, 16ths, Quick-Reading 32nds, 64ths C370-12 51428 1/8" C389-12 51473 12" 1 x 3/64" 5/32" 4R – 8ths, 16ths, Quick-Reading 32nds, 64ths C100F-12 50458 12" 1 x 3/64" 3/16" 6R – Aircraft Quick-Reading 50ths (.02) Both Edges One Side; Quick-Reading 10ths (.10); Both Edges Opposite Side C375-12 51432 12" 1 x 3/64" 3/16" 4R – 8ths, 16ths, Quick-Reading 32nds, 64ths C376-12 51434 7/32" C377-12 51435 1/4" C378-12 51437 9/32" C368-12 51424 5/16" C374-24 51431 24" 1-1/4 x 3/64" 1/10" 4R – 8ths, 16ths, Quick-Reading 32nds, 64ths C370-24 51429 1/8" C389-24 51474 5/32" C100F-24 50459 24" 1-1/4 x 3/64" 3/16" 6R – Aircraft Quick-Reading 50ths (.02) Both Edges One Side; Quick-Reading 10ths (.10); Both Edges Opposite Side C375-24 51433 24" 1-1/4 x 3/64" 3/16" 4R – 8ths, 16ths, Quick-Reading 32nds, 64ths C377-24 51436 1/4" C368-24 51425 5/16" Steel Rules Steel Rules with Shrink Gradua tions 12", 24" These spring-tempered, satin chrome finished shrink rules are for laying out wood and metal patterns and core boxes for casting metals. Graduated to give shrink allowances directly, they come in 12" and 24" lengths with shrinks from 1/16-3/8" per foot. The average shrinkage figures are for metals cast with uniform sections under normal conditions (see table).When using, be sure that the size and shape of castings are considered, since thick castings have less shrink and thin castings more shrink than the figures shown. NOTE: Also see 62 Rule Holder. A very useful tool for patternmakers. Average Shrinkage of Castings (Inches per Foot) Cast Iron 1/8" Malleable Iron 1/8" Steel 1/4" Brass 3/16" Copper 3/16" Aluminum 3/16" Lead 5/16" Zinc 5/16" Britannia 1/32" Tin Alloys 1/12" C375-12 297 starrett.com P recision R ules , S traight E dges , P arallels