Marking out, cutting and machining: HSC Industrial Technology Metal and Engineering
“Describe the processes and tools used to mark out, cut, drill and machine metal, including the centre lathe, milling machine and drill press, and explain accurate measurement and their safe operation”
Metal work begins with accurate measurement and marking out using rules, vernier and micrometer instruments, scribers and centre punches. Material is removed by cutting (hacksaw, shears, snips), drilling, and machining. The centre lathe turns cylindrical work by rotating it against a tool; the milling machine cuts flat surfaces, slots and profiles with a rotating cutter; the drill press bores holes. Accuracy, correct speeds and feeds, cutting fluid and machine guarding govern good, safe results.
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What this dot point is asking
Engineering depends on accurate marking out and material-removal processes that cut metal to precise shapes and sizes. NESA expects you to describe the tools and processes used to measure, mark out, cut, drill and machine metal, including the centre lathe, milling machine and drill press, and to explain accurate measurement and safe operation. This is core production knowledge for the focus area, tested in the written paper and demonstrated in the precision of your Major Project.
Measurement and marking out
Engineering tolerances are tight, so measurement matters. Steel rules give rough lengths, while vernier calipers and micrometers read to fractions of a millimetre for precise work. Marking out transfers dimensions onto the metal: a scriber scratches lines, a centre punch marks hole centres so a drill does not wander, dividers scribe arcs, and engineers squares and surface plates establish reference faces. Engineers blue makes scribed lines visible. Marking from a single datum edge keeps errors from accumulating.
Cutting and drilling
Material is removed first by cutting to rough size and then by machining to final size:
- Sawing: the hacksaw and powered bandsaw cut bar and section to length.
- Shearing: guillotines, snips and shears cut sheet metal cleanly.
- Drilling: the drill press bores holes; the work is clamped, the correct speed is set for the material and drill size, and cutting fluid cools the bit.
The centre lathe
The centre lathe is the foundation machine of engineering. It rotates the workpiece while a single-point tool is fed against it to remove metal, producing cylindrical and conical shapes. Common lathe operations include turning a diameter down, facing the end square, drilling and boring holes on the centre, cutting threads and parting off. Correct spindle speed, feed rate and tool height, plus cutting fluid, give an accurate, well-finished surface.
The milling machine
The milling machine uses a rotating multi-tooth cutter to remove metal from a workpiece clamped to a moving table. It cuts flat faces, steps, slots, grooves and complex profiles that the lathe cannot. The table moves in several axes to position the work under the cutter, and modern CNC milling automates this for accurate, repeatable production.
Swarf, speeds, feeds and cutting fluid
Machining produces hot metal chips called swarf, which are sharp and must never be cleared by hand while a machine runs. The cutting speed and feed rate are matched to the material and tool: too fast burns the tool, too slow wastes time and gives a poor finish. Cutting fluid cools and lubricates the cut, extends tool life and improves finish. These factors decide both quality and tool wear.
Machine safety
Machining safety shares clear principles. Clamp the work securely; never hold it by hand against a cutter. Keep guards in place and remove chuck keys before starting a lathe. Wear eye protection and remove gloves, ties, loose clothing and jewellery that could be caught by rotating parts, and tie back long hair. Never clear swarf or take measurements while the machine runs, and only operate machines you are trained and authorised to use. Stop the machine before adjusting or measuring.
On a centre lathe the work rotates and the tool stays still, producing round shapes; on a milling machine the cutter rotates and the work is fed past it, producing flat faces, slots and profiles. Knowing which machine rotates which part is the key to choosing the right one for a component.
- Clearing swarf by hand
- Hot, razor-sharp chips must be cleared with a brush and only when the machine is stopped.
- Leaving the chuck key in
- A chuck key left in a lathe becomes a projectile on start-up; remove it every time.
- Wrong speeds and feeds
- Running too fast or slow burns tools and ruins finish; match speed to material and tool.
- Wearing gloves at the lathe
- Gloves and loose items can be dragged into rotating work; remove them when machining.
Exam-style questions
Questions in the style of NESA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
2019 HSC-style1 markWhat is the main purpose of centre punching a piece of metal prior to drilling a hole? A. To prevent wandering B. To create a pool for lubricant C. To speed up the drilling process D. To break the surface tension of the metalShow worked answer →
The correct answer is A: to prevent wandering.
A centre punch is struck to make a small conical indentation exactly on the marked-out hole centre. This indent gives the point of the drill bit a location to start in, so the drill bites at the correct spot and the tip cannot slip or skate across the surface as it begins to cut. That is why centre punching is done before drilling.
It is not done to hold lubricant (B), to make drilling faster (C), or to affect any surface tension (D). Its single purpose is accurate location of the hole, so A is correct.
2021 HSC-style1 markWhich is the most suitable chuck to use when setting up heavy and irregular shaped work? A. Scroll chuck B. Keyless chuck C. Three jaw universal chuck D. Four jaw independent chuckShow worked answer →
The correct answer is D: four jaw independent chuck.
In a four jaw independent chuck each jaw is adjusted separately. This lets the operator clamp heavy, off-centre or irregular shaped work securely and dial it in to run true, and the strong independent grip suits heavy work. That makes it the most suitable choice here.
A three jaw universal chuck (and the scroll chuck that drives it) self-centres round or hexagonal stock but cannot grip irregular shapes accurately, and a keyless chuck is a light-duty drill chuck. So D is correct.
2019 HSC-style4 marksProvide a procedure for centring a piece of bright round bar (30 mm diameter x 50 mm long) in a four-jaw chuck prior to machining the end.Show worked answer →
A four-mark answer should give a clear, ordered procedure.
Mount the work. Open the four independent jaws and seat the bar in the chuck, leaving enough projecting to machine the end, then nip each jaw up by hand so the bar is roughly central, using the concentric scroll rings on the chuck face as a rough guide.
Set up to indicate. Mount a dial test indicator on the lathe so its stylus touches the outside of the bar, then rotate the chuck slowly by hand and watch the needle to find the high and low points.
True it up. Adjust the opposing jaws, slackening one and tightening the one opposite, to move the high spot towards centre. Re-check with the indicator and repeat.
Finish. Continue until the indicator shows minimal run-out through a full rotation, then firmly tighten all jaws evenly. The bar now runs true and the end can be faced or machined.
Marks reward the use of a dial indicator and the iterative adjustment of opposing jaws to remove run-out.