Polytechnic · Fabrication Engineering Drawing · Interactive drawing lesson

Extension line

Brings a feature out to its size. Learn extension line step by step in an interactive Polytechnic fabrication engineering drawing lesson.

What you will learn

This guided practical demonstrates the construction on a drawing board and explains the method in a clear sequence.

Open the interactive drawing lesson

More Fabrication Engineering Drawing lessons

• Full size (1:1) — The drawing and the job are the same.
• Reduction scale (1:2) — Half size, with true figures on it.
• Enlargement scale (2:1) — A small part drawn twice size.
• Dual scale — Metres and feet off one bar.
• Diagonal scale — Three orders of size from one scale.
• Plain scale — Whole units and tenths.
• Stepped block in third angle — Plan above, end view on the left.
• Stepped block in first angle — Plan below, end view on the right.
• Auxiliary views — True shape of a sloping face.
• Outline — Continuous thick — the visible edges.
• Centre line — Chain thin, through every hole and axis.
• Projection line — Carries a point between views.
• Construction line — The setting out you leave on.
• Dimension line — Arrowheads, spacing and the figure.
• Leader line — Takes a note to a feature.
• Limit line — Where a partial view stops.
• Phantom line — An alternate position, in chain double dash.
• Extension line — Brings a feature out to its size.
• Break line — A long bar drawn short.
• Cutting plane line — Where the job was cut open.
• Hidden detail line — An edge behind the metal.
• Open style lettering — Upright capitals at full width.
• Condensed style lettering — Narrowed to fit a tight box.
• Sloping style lettering — Capitals leaning 15°.
• Open style lower case — x-height, ascenders and descenders.
• Open style freehand — The same hand with no straight edge.
• Sloping style freehand — Leaning letters, freehand.
• Matchstick man and woman — A freehand proportion exercise.
• Isometric axis sketch — Three axes, 120° apart, freehand.
• Most representative views — Choosing the front view and top view.
• Isometric to first angle — Read a pictorial, draw three views.
• Cylinder cut by a plane — The first template: a mitred pipe.
• Junction of equal cylinders — A tee that meets in straight lines.
• Rake of a ship funnel — A cylinder cut by two sloping planes.
• Plates for a boiler dome — A dome saddled onto a curved shell.
• Boiler to superheater pipe — One pipe, saddled at both ends.
• Overhanging boiler front — A flanged blank and its bend allowance.
• Plates of an egg-ended boiler — Barrel strakes and end gores.
• Frustum not continued to a point — A taper whose apex is off the board.
• Rise and radius of a cone — Arcs bigger than your compass.