Determine the shrink rule to be used by pattern makers for m

Determine the shrink rule to be used by pattern makers for magnesium. using the shrinkage value in the table, express your answer in terms of decimal fraction inches of elongation per foot of length compared to a standard one-foot scale.

Solution

For, Magnesium linear shrinkage is 2.1% (from the attached table)

So, Linear contraction = 1 - (2.1/100) = 0.979

Shrink rule elongation = (0.979)^-1 = 1.02145

For a 1 foot rule, L = 1.02145 * (12) = 12.2574 inch ( 1 foot = 12 inch)

Therefore, Inches of elongation per foot length = 12.2574 - 12 = 0.2574 inch