Lathe and Machine Tool Operations
Core Concepts
The lathe is central. Know its parts: bed, headstock, tailstock, carriage, cross-slide, compound rest, tool post, lead screw, feed rod, and chuck. Understand operations: facing, turning, taper turning, threading, boring, drilling, knurling, parting off, and chamfering. Know how to set spindle speed, feed, and depth of cut, and how to calculate taper and thread dimensions.
Machine Tools
Know the drilling machine (radial, pillar, sensitive), milling machine (horizontal/vertical, up-cut vs down-cut), shaping machine (stroke, quick return), and grinding (surface, cylindrical). Understand work-holding: three-jaw chuck (self-centring), four-jaw chuck (independent), collets, faceplate, and centres. Traps include confusing up-milling with down-milling, mixing taper formulas, or forgetting that a three-jaw chuck cannot hold irregular work without packing.
Worked Example / Rule of Thumb
Taper turning by swivelling the compound rest: half-angle = taper angle/2. For a taper of 1:10, the included angle is about 5.72°, so swivel ≈ 2.86°. For thread cutting, the pitch determines the lead screw gearing: gear ratio = pitch of work / pitch of lead screw. For turning, use the cutting speed formula and reduce speed for harder materials.
Maintenance
Core Concepts
Maintenance covers preventive and breakdown maintenance, lubrication, alignment, and machine care. Know lubrication types (oil, grease, dry film), lubricant properties (viscosity, flash point, additives), and the purpose of lubrication: reduce friction and wear, remove heat, and protect against corrosion. Understand bearing types (plain, ball, roller, thrust) and their failure signs: noise, heat, vibration, and play.
Machine Care and Traps
Know daily checks: oil levels, coolant condition, belt tension, guards, and cleanliness. Understand the difference between preventive (scheduled) and predictive (condition-based) maintenance. Traps include confusing grease with oil for high-speed bearings, ignoring coolant contamination, or assuming more oil is always better. Learn about backlash adjustment in lead screws, gib adjustment for slides, and alignment checks with dial indicators.
Worked Example / Rule of Thumb
Rule of thumb: over-greasing can cause bearing overheating as much as under-lubrication; follow the manufacturer's quantity. For a plain bearing, check clearance with a feeler gauge or by the 'rock' test. Record lubricant type and interval in the maintenance log. If a bearing runs hot, stop the machine, check alignment and lubrication, and do not simply add more oil.
Materials and Trade Practice
Core Concepts
Know ferrous and non-ferrous metals: plain carbon steel, alloy steel, cast iron, stainless steel, aluminium, copper, brass, bronze. Understand properties: hardness, toughness, ductility, malleability, brittleness, and machinability. Know heat treatment: annealing, normalising, hardening, tempering, and case hardening. Know how carbon content affects hardness and machinability.
Trade Practice and Traps
Understand workshop organisation, job cards, inspection, quality control, and safe disposal of waste. Know standard material forms (bar, plate, sheet, tube) and how to identify them. Traps include confusing annealing (soften) with hardening (quench), mixing malleability (ability to be hammered into sheets) with ductility (drawn into wire), or assuming stainless steel cannot rust. Also know the effect of alloying elements: carbon increases hardness, chromium improves corrosion resistance, nickel improves toughness.
Worked Example / Rule of Thumb
Rule of thumb: low-carbon steel (up to ~0.3% C) is easily machined and welded; medium carbon (~0.3–0.6%) can be hardened and tempered; high carbon (>0.6%) is hard and wear-resistant but brittle. For hardening, heat to the correct temperature, quench in the specified medium, then temper immediately to relieve stress. Always follow the job card and inspection plan.