Workshop Technology
Complete Notes — Easy English

What is a Workshop?

A workshop is a place where workers use machines and hand tools to make, repair, or change metal and other materials. In DAE Mechanical, you will spend a lot of time in the workshop doing practical work.

Types of Workshops

Workshop Safety Rules

• Always wear safety glasses to protect your eyes from flying chips.
• Wear safety shoes — heavy parts can fall on your feet.
• Never wear loose clothes near machines — they can get caught.
• Keep the workshop floor clean and dry — oil spills cause slipping.
• Never run or play in the workshop.
• Always switch off machines when not in use.
• Do not touch a machine you do not know how to use.
• Know where the fire extinguisher and first aid box are kept.

Personal Protective Equipment (PPE)

First Aid in Workshop

• Eye injury: Wash eye with clean water immediately. Do not rub.
• Cut: Press a clean cloth on the wound and go to a doctor.
• Burn: Put the burned area under cold running water for 10 minutes.
• Electric shock: Switch off power first, then help the person — do NOT touch them while power is on.
• Fire: Use fire extinguisher. Shout for help. Leave the building.

Why Measurement is Important

In a workshop, accurate measurement is very important. If you cut a piece too short or too long, the whole part becomes useless. The saying in workshop is: "Measure twice, cut once."

Types of Measuring Tools

Vernier Caliper — Reading Steps

• Step 1: Read the main scale reading (mm) before the 0 of the vernier scale.
• Step 2: Find which vernier division lines up exactly with the main scale.
• Step 3: Multiply that number by 0.02.
• Step 4: Add both readings. That is your answer.

Micrometer

A micrometer (also called a screw gauge) measures very small sizes very accurately — up to 0.01 mm. It works by turning a screw. One full turn of the thimble moves it 0.5 mm. It has a sleeve (main scale) and a thimble (small scale).

Marking Tools

Marking Media

Before marking, the metal surface is coated with a marking media so the scribed lines are easy to see. Common types: chalk (for rough work), engineer's blue / Prussian blue (for accurate work on smooth metal), and white paint (for dark metals).

What is Bench Work?

Bench work means the work done on a workbench using hand tools — without machines. It includes filing, sawing, chiseling, and scraping. These are some of the most important basic skills every mechanical engineer must learn.

Filing

A file is a hard steel tool with many small teeth. It is used to remove extra material from a metal surface to make it smooth and the correct size.

File cuts (grades): Rough (removes most material) → Bastard → Second Cut → Smooth (gives fine finish)

Hacksawing

A hacksaw is used to cut metal. It has a metal frame and a removable blade with teeth. The blade is fitted with teeth pointing forward — cutting happens on the forward stroke only (push stroke).

• Hold the hacksaw with both hands — one on the handle, one on the front frame.
• Use full blade length on each stroke for better cutting.
• Apply pressure on the forward stroke only — lift slightly on the return stroke.
• For thin material: use a blade with more teeth per inch (finer blade).
• For soft/thick material: use a blade with fewer teeth (coarser blade).

Chiseling

A chisel is used with a hammer to cut or chip away metal. It is made of hardened steel.

Vise (Vice)

A bench vise is used to hold the metal workpiece tightly while you file, saw, or chisel it. It is bolted to the workbench. The jaws grip the metal when you tighten the handle. Always use soft jaw covers (aluminium or copper pads) on the jaws when holding finished parts so they do not get scratched.

What is Drilling?

Drilling is the process of making a round hole in a material using a rotating cutting tool called a drill bit. It is one of the most common operations in any workshop.

Types of Drilling Machines

Parts of a Drilling Machine

• Base — the bottom support of the machine
• Column / Pillar — the vertical post that holds everything
• Table — where the workpiece is placed (can be raised or lowered)
• Spindle — the rotating part that holds the drill bit
• Chuck — grips and holds the drill bit
• Chuck Key — used to tighten or loosen the chuck
• Feed Handle — you push this down to lower the drill into the work
• Motor — gives power to rotate the spindle

Types of Drill Bits

Steps for Safe Drilling

• Mark the centre of the hole with a centre punch first.
• Secure the workpiece firmly in a vise or clamp — never hold it by hand.
• Select the correct drill bit size and tighten it in the chuck with the chuck key.
• Remove the chuck key before starting the machine.
• Start the drill and slowly lower the drill bit onto the marked centre.
• Apply light oil (cutting fluid) to cool the drill bit and help it cut better.
• Lift the drill bit out regularly to remove chips and prevent overheating.

What is a Lathe?

A lathe is a machine that spins a metal workpiece (job) while a cutting tool removes material from it to produce a desired shape — usually a cylinder or round part. It is called the "mother of all machines" because many other machines can be made using a lathe.

Main Parts of a Lathe

Types of Lathe Operations

Types of Lathe Chucks

• 3-Jaw Chuck (Self-Centering) — all 3 jaws move together automatically. Best for round and hexagonal work. Very quick to use.
• 4-Jaw Chuck (Independent) — each jaw moves separately. Used for square, irregular, or off-center work. More accurate but slower to set up.
• Face Plate — flat disc with slots for bolting irregular shaped parts.

Lathe Safety Rules

• Always wear safety glasses near the lathe.
• Never wear gloves when operating a lathe — they can get caught in the rotating chuck.
• Make sure the workpiece is firmly clamped before starting.
• Remove the chuck key before switching on the machine.
• Never measure or touch the rotating workpiece.
• Use a hook or brush to remove metal chips — never your hand.

What is Welding?

Welding is a process of permanently joining two or more pieces of metal by heating them until they melt and fuse together. A filler material (electrode or filler rod) is usually added to make a strong joint.

Types of Welding

Arc Welding (SMAW) — Process

In arc welding, an electric arc (a spark of electricity) is created between a coated metal electrode and the workpiece. This arc produces very high heat (around 3500°C) which melts the metal. The coating on the electrode burns and produces a gas cloud that protects the weld from air (oxygen).

• Electrode — the metal stick used in arc welding
• Electrode holder — holds the electrode safely
• Earth clamp — connects the workpiece to the welding machine
• Slag — the hard crust that forms on the weld after cooling — must be chipped off

Types of Welding Joints

Common Welding Defects

Welding Safety

• Always wear a welding helmet — the arc is so bright it can permanently damage your eyes.
• Wear leather gloves, apron, and safety shoes.
• Weld in a well-ventilated area — welding fumes are dangerous to breathe.
• Never look at the arc without a proper welding helmet.
• Keep a fire extinguisher nearby.

What is Sheet Metal Work?

Sheet metal work is the process of cutting, bending, and joining thin metal sheets (usually less than 6 mm thick) to make items like boxes, pipes, ducts, and trays. Common metals used: mild steel, aluminium, copper, and galvanized iron (GI).

Sheet Metal Tools

Sheet Metal Operations

Sheet Metal Joints

• Grooved Seam — the edges of two sheets are folded and locked together — used for boxes and cans
• Lap Seam — one sheet overlaps the other and is riveted or soldered
• Standing Seam — both edges are folded up and bent together — used for roofing
• Wired Edge — a wire is rolled inside the edge of a sheet for strength — used on buckets

Common Sheet Metal Products

What is Fitting?

Fitting is the process of making a part to an exact size and shape so that it correctly fits with another part. A fitter (the worker) uses hand tools and measuring instruments to do this work.

Types of Fits

Tolerance and Allowance

• Tolerance — the small allowed difference between the maximum and minimum size of a part. Example: a shaft should be 25 mm ± 0.05 mm — it can be anywhere between 24.95 mm and 25.05 mm.
• Allowance — the planned (intentional) difference between the sizes of two mating parts (hole and shaft).
• Limit — the maximum or minimum allowed size of a part.

Fitting Tools

Tapping and Threading

• Tapping — making a screw thread inside a hole using a cutting tool called a tap. The steps are: drill the correct size hole → insert tap → turn clockwise half a turn, then anti-clockwise quarter turn to break chips → keep going until thread is complete.
• Threading / Die cutting — making an outside thread on a round rod using a tool called a die. The rod must be the correct diameter before threading.

What are Fasteners?

Fasteners are devices used to join two or more parts together. They can be temporary (can be removed later, like bolts and screws) or permanent (cannot be easily removed, like rivets and welding).

Types of Temporary Fasteners

Types of Screw Threads

Thread Terms

• Pitch — the distance between two thread peaks (in mm)
• Lead — how far the nut or bolt moves in one full turn
• Major Diameter — the largest diameter of the thread
• Minor Diameter — the smallest diameter of the thread (at the root)
• TPI (Threads Per Inch) — used in the inch system

Rivets — Permanent Fasteners

A rivet is a permanent fastener — once it is fitted, it cannot be removed without destroying it. It is a short metal pin with a head on one end. The other end is hammered (or pressed) to form a second head, locking the joint.

Locking Devices (Preventing Nuts from Loosening)

• Lock Nut — a second nut tightened against the first
• Spring Washer — a split washer that grips and prevents loosening
• Castle Nut + Cotter Pin — nut has slots, pin goes through to lock it
• Locking Wire — wire threaded through bolt heads to prevent rotation

What is Heat Treatment?

Heat treatment is the process of heating a metal to a specific temperature and then cooling it in a specific way to change its properties — making it harder, softer, stronger, or more flexible.

Heat Treatment Processes

Quenching Media (Cooling Liquids)

• Water — very fast cooling, gives maximum hardness — used for plain carbon steel
• Oil — slower cooling than water — less distortion/cracking — used for alloy steel
• Air — slowest cooling — used for normalizing
• Brine (Salt Water) — faster than plain water — used for special steels

Why Tempering is Done After Hardening?

After hardening, steel becomes very hard but also very brittle (it breaks easily like glass). Tempering is done to reduce this brittleness while keeping most of the hardness. The colour of the surface during tempering tells the temperature: straw (220°C) → light blue (290°C) → blue-black (320°C).

Case Hardening — Method

• Carburizing — steel part is packed in carbon-rich material and heated — carbon enters the surface
• Nitriding — steel is heated in nitrogen gas — nitrogen enters the surface to harden it
• Result: hard outer skin (5–15 mm) + tough/soft core — perfect for gears, cams, shafts

What is a Pattern?

A pattern is a model or replica of the final product. It is used to make a mould in sand. Liquid metal is then poured into the mould. When the metal cools and solidifies, it takes the shape of the pattern. The process of making parts this way is called casting.

Pattern Materials

Types of Patterns

Pattern Allowances

A pattern is always made slightly larger than the final part because of these allowances:

• Shrinkage Allowance — metal shrinks (gets smaller) as it cools. The pattern is made bigger to compensate. Example: cast iron shrinks about 10 mm per metre.
• Draft Allowance (Taper) — sides of the pattern are given a slight taper (angle) so the pattern can be easily removed from the sand mould without breaking it.
• Machining Allowance — extra material added on surfaces that will be machined later to the final smooth finish.
• Distortion Allowance — for parts that are expected to bend or warp during cooling — the pattern is made with an opposite curve.

Workshop Project Guidelines

At the end of the Workshop Technology course, you will complete a practical project. You will use the skills learned in this course to make a real metal part. Follow these steps:

• Step 1 — Choose a Job: Select a simple project like a metal tray, bracket, T-square, or step block.
• Step 2 — Make a Drawing: Draw the part with all dimensions (Engineering Drawing rules).
• Step 3 — Select Material: Mild steel is best for beginners.
• Step 4 — Mark Out: Use scriber, square, and divider to mark all dimensions on the metal.
• Step 5 — Cut to Size: Use hacksaw to cut the material close to the marked lines.
• Step 6 — File to Finish: File all surfaces to the exact size and check with Vernier caliper.
• Step 7 — Drill if Needed: Mark centre points, punch, and drill any holes.
• Step 8 — Finish: Deburr all edges, clean the surface, apply paint or oil.

Workshop Technology — Complete Course Summary