Reading drawings & cutting lists
Practical Woodworking · National 5 · mrkellydt.co.uk
What you're learning in this topic
Learning intention WALT
We are learning about reading drawings & cutting lists, specifically to:
understand
- orthographic projection, scale and line types, including hidden detail
be able to
- read working drawings with linear, radial (R), diametric (Ø) and angular dimensions
- read and use a cutting list
- calculate lengths of timber and plan cutting to reduce waste
Success criteria WILF
- I can read working drawings with linear, radial (R), diametric (Ø) and angular dimensions
- I can read and use a cutting list
- I can calculate lengths of timber and plan cutting to reduce waste
Working drawings
A working drawing gives every size you need to make the product. In the practical activity you must work to the drawings exactly: you can't be given extra drawings or dimensions.
- Orthographic projection: separate flat views (elevation, end elevation, plan) lined up with each other.
- Pictorial drawing: a 3D view (e.g. isometric) that shows what the product looks like.
- Exploded view: parts pulled apart to show how they fit together.
Dimensions and symbols
- All sizes are in millimetres.
- Linear dimensions show lengths; radial dimensions use R (R10 = radius 10 mm); diametric use Ø (Ø20 = diameter 20 mm); angular dimensions show degrees.
- Scale: 1:2 means the drawing is half full size; 2:1 is twice full size; 1:1 is full size.
- Ratio dimensions: e.g. a tenon is usually one third of the thickness of the wood.
Line types
| Line | Used for |
|---|---|
| Thick continuous | Outlines and visible edges |
| Thin continuous | Dimension and projection lines |
| Thin dashed | Hidden detail (edges you can't see) |
| Thin chain (long dash, dot) | Centre lines |
Cutting lists
A cutting list lists every part with its length × breadth × thickness, the number needed and the material. Length is always given first, along the grain.
To find the total length of timber: multiply each part's length by how many you need, add them up, and allow for waste at the ends. Laying parts out carefully on the board reduces waste.
In the practical activity, lengths and breadths must never change. Thickness can change only if the exact size isn't available, and then the drawings must be amended.
Key terms
| Ø20 | Diameter 20 mm |
|---|---|
| R10 | Radius 10 mm |
| Hidden detail line | Thin dashed line: shows edges you can't see |
| Centre line | Thin chain line (long dash, short dash) |
| Scale 1:2 | The drawing is half full size |
| Cutting list order | Length × breadth × thickness |
| Orthographic projection | Flat views (elevation, end elevation, plan) lined up with each other |
| Ratio dimension for a tenon | About one third of the thickness of the wood |
Quick check
1. What does Ø25 mean on a drawing?
- Radius 25 mm
- Diameter 25 mm
- 25 degrees
- Depth 25 mm
Show answer
2. Which line type shows hidden detail?
- Thick continuous
- Thin chain
- Thin dashed
- Thin continuous
Show answer
3. A drawing at 1:2 is…
- Twice full size
- Full size
- A quarter full size
- Half full size
Show answer
4. On a cutting list, which size comes first?
- Length
- Breadth
- Thickness
- Diameter
Show answer
5. In the practical activity, which sizes must never be altered?
- The thickness of each part only
- Lengths and breadths
- The overall height of the product
- None: any size can be changed
Show answer
Printable worksheet
An I do, we do, you do worksheet for this topic, with a separate answer sheet.