Workshop Practice and Manufacturing Processes
Workshop Practice and Manufacturing Processes tests bench work, measurement, basic machining, joining and casting at shop-floor level: which tool for which job, how to read a vernier or micrometer, standard lathe and drilling operations, and the difference between welding, brazing and soldering.
Core rules
- Bench work sequence: mark out with a scriber and surface plate, centre-punch, then file or saw. A hacksaw needs at least three teeth in contact with the work, so thin sections need fine teeth (24–32 TPI).
- Vernier least count = value of one main-scale division ÷ number of vernier divisions. Micrometer least count = pitch ÷ thimble divisions.
- Tapping drill size ≈ major diameter − pitch (M10 × 1.5 gives 8.5 mm).
- Lathe operations: turning, facing, taper turning (swivelling the compound slide, tailstock set-over or taper attachment), thread cutting through the lead screw and half-nut.
- Welding is a coalescence process with parent metal melting (arc, MIG, TIG); brazing and soldering use a filler that melts below the parent metal's melting point (brazing above 450 °C, soldering below).
Worked example
A vernier caliper has a main scale of 1 mm divided into 2 parts (0.5 mm) and a vernier of 25 divisions. Least count = 0.5 ÷ 25 = 0.02 mm. The main scale reads 12.0 mm and the 13th vernier line coincides. Reading = 12.00 + (13 × 0.02) = 12.26 mm. If the caliper has a zero error of +0.02 mm, the corrected reading is 12.24 mm.
Traps that cost marks
Ignoring zero error; gripping the job loosely or measuring over a burr; choosing a coarse blade for thin tube; forgetting that depth of cut and feed are different; assuming solder melts the parent metal.