Principles of Fabrication · Lesson 02
Common Workshop Machines and Operations
Before computer-controlled manufacturing became common, most fabrication depended on machines whose movement was directly controlled by an operator.
These machines are still fundamental to modern workshops.
Understanding what they do makes more advanced manufacturing processes much easier to understand.
Saws
A saw separates material by moving a toothed blade through it.
Different saws arrange that motion differently.
Jigsaw
A jigsaw uses a narrow blade moving rapidly up and down.
Its small blade allows it to follow curved paths and cut shapes that would be difficult with a large circular blade.
It is generally used where flexibility is more important than extremely rigid, high-volume cutting.
Circular saw
A circular saw uses a rotating disc-shaped blade.
Hand-held circular saws are commonly used to make relatively straight cuts through sheet and structural materials.
The operator moves the saw through the workpiece.
Table saw
A table saw places a circular blade in a fixed machine table and the workpiece is guided past it.
This allows accurate repeated straight cuts, particularly in timber and sheet products.
Because the operator moves material toward a powerful exposed cutting system, guarding, correct setup and controlled workholding or guiding are especially important.
Drop saw and mitre saw
A drop saw moves a rotating blade downward through a stationary workpiece.
A mitre saw adds the ability to make angled cuts.
They are commonly used to cut stock such as timber, aluminium sections and other suitable profiles to length.
Bandsaw
A bandsaw uses a continuous loop of toothed blade running around wheels.
Depending on the machine and blade, bandsaws can be used for straight cuts, curves, profile cutting and cutting metal stock.
Drilling machines
A drill removes material using a rotating cutting tool.
A hand drill is moved and supported by the operator.
A pedestal drill or drill press instead holds the drill spindle in a rigid machine frame and moves the cutting tool along a controlled axis.
This improves alignment and repeatability.
The workpiece still needs to be controlled. If a drill catches a loosely held part, the part itself can begin rotating.
Machine accuracy means very little if the work can move.
Lathes
A lathe reverses the relationship people often imagine between the tool and the workpiece.
Instead of moving a rotating cutting tool through stationary material, a conventional lathe rotates the workpiece while a cutting tool is brought against it.
This naturally produces cylindrical geometry.
Typical lathe operations include turning an outside diameter, facing the end of a part, boring internal features and producing threads.
Lathes are extremely useful machines, but rotating workpieces, chucks and spindles create serious entanglement hazards. Clothing, hair, jewellery, gloves and loose objects must be considered accordingly.
Taps and dies
Threaded fasteners depend on matching internal and external threads.
A tap produces an internal thread inside a correctly prepared hole.
A die produces an external thread around suitable round stock.
The dimensions matter. A tapped hole needs enough remaining material to form the thread, which means the drilled hole before tapping is normally smaller than the final nominal thread diameter.
Threads are another example of fabrication geometry depending on the manufacturing process rather than simply on the final visible shape.
Grinders and abrasive tools
Not all cutting requires a toothed blade.
Grinding and abrasive processes remove material using large numbers of hard abrasive particles.
Bench grinders, angle grinders, linishers and other abrasive machines can be used for shaping, smoothing, deburring, sharpening and surface preparation.
They can also generate sparks, noise, heat and airborne particles.
The abrasive wheel or disc itself is a manufactured tool with operating limits and must be suitable for the machine and material.
Welding
Welding joins materials by producing a metallurgical bond, usually using heat.
Rather than removing material to create a shape, welding allows multiple fabricated parts to become a larger structure.
Common processes include:
MIG welding, where a continuously fed wire electrode forms part of the weld.
TIG welding, where a non-consumable tungsten electrode produces the arc and filler material can be introduced separately where required.
Stick welding, where a consumable coated electrode produces the arc and supplies filler material.
Different welding processes suit different materials, thicknesses, environments and quality requirements.
Welding also introduces hazards beyond the hot metal itself. Arc radiation, fumes, sparks, electrical equipment and fire risk all have to be controlled.
Welding also changes the workpiece.
Heating and cooling can cause expansion, contraction and distortion. A perfectly aligned assembly before welding may move as the weld cools.
Fixtures, clamps and welding sequence can therefore affect the finished geometry.
The common principle
A saw, drill, lathe, grinder and welder may look completely different, but they all require the operator to understand the relationship between:
machine + tool + material + workholding + human
Change any one of those and the behaviour of the operation can change.