Workshop calculation, applied science and measuring instruments
Domain 11 - Workshop calculation, applied science and measuring instruments
This domain tests numerical problems used in the foundry and the correct use of measuring instruments, together with basic applied science.
Calculations and science
Typical calculations include pattern allowances, gating ratios, riser modulus, charge mixing, sand moisture, volume and surface area, density and buoyancy, and cost. Useful relations: density = mass/volume; thermal expansion ΔL = LαΔT; heat Q = mcΔT plus latent heat at a phase change; continuity A1V1 = A2V2. Conversion: °F = (1.8 × °C) + 32; K = °C + 273.
Measuring instruments
Steel rule, vernier calliper, micrometer, height gauge, try square, bevel protractor and dial indicator. A vernier calliper with a 1 mm main scale and 50 vernier divisions has a least count of 1/50 = 0.02 mm. A metric micrometer with a 0.5 mm pitch and a thimble of 50 divisions has a least count of 0.5/50 = 0.01 mm. Check zero error before use.
Worked example
A vernier calliper reads 12 mm on the main scale, and the 14th vernier division coincides with a main-scale line. Least count = 0.02 mm. Vernier reading = 14 × 0.02 = 0.28 mm. Total = 12.28 mm. If the instrument has a zero error of +0.03 mm, the corrected reading is 12.28 − 0.03 = 12.25 mm.
Traps
Do not add the vernier division number directly as a decimal. Keep units consistent: cm, mm and m cannot be mixed in one formula. In shrinkage problems, apply the allowance to the correct base dimension. For temperature conversion, do not use 1.8 × (C + 32). A micrometer reads to 0.01 mm, not 0.1 mm.