Isometric Drawing

Isometric Projection Drawing

DZULKIFLI AWANG, PHD

Chapter 6

Content

• Overview

– Pictorial projection

– Parallel projection

– Axonometric projection

• Isometric projection

– Axes and selection

– Isometric lines and planes

– Isometric scale

– Isometric projection & Isometric drawing

• Producing Isometric sketches & drawing

– Isometric lines & non-isometric lines

– Circles and arcs

– Irregular curves

• Oblique projection drawing

3.1 Pictorial projection

• Pictorial projection: – Not intended to give

exact or true view.

– Not intended to transmit dimensions, although sometimes dimension is useful.

– Useful when the information and instructions to be given to non-technical and untrained people.

– Hidden lines are not shown in isometric drawing.

3.1 Parallel projection technique

3.1 Axonometric projection

• axon = axis; metric = measure, in Greek

• Axonometric projection is a parallel

projection technique to create a pictorial drawing of an object by rotating the object

on an axis relative to a projection or picture

plane


• Axonometric projection

– Trimetric

– Dimetric

– Isometric

Axonometric Projections

3.2 Isometric projection

• Isometric projection is a true representation of the isometric view of an object

• Isometric view is created by rotating the object 45

degree about vertical axis, and tilting it forward 35 deg 16’

3.2 Isometric projection: axes

• The 3 axis meet at A,B form equal angles of

120 deg and they are called Isometric Axes

• OA is vertical, OB is inclined at 30deg to the right, OC is inclined at 30deg to the left

• Any lines parallel to these – Isometric Line

• Any planes parallel – Isometric Planes

Selection of Isometric Axes

• Main purpose of isometric view is to provide a pictorial view which reveals as much detail as possible

• Selection of principal edges is important

• Figure shows different isometric views of the same block

Isometric projection: scale

• The tilt causes the edges & planes to

become foreshortened

• The projected length is approximately 80% of the true length

Isometric projection & drawing

• Isometric projection & Isometric drawing

– Isometric projection: drawn at scale of 0.816

– Isometric drawing: drawn at full scale

Isometric Projection vs. Sketch

Isometric projections are foreshortened because the object is tipped

with respect to the viewing plane. Isometric sketches are not usually

foreshortened because they still appear proportionate when showing

the dimensions full size along isometric axis lines. It is easier just to

sketch the full dimension.

Iso-lines & Iso-planes: examples

Non-isometric lines

• Non-isometric lines are the lines that are not parallel to any of the iso-lines.

• They are drawn by transferring the distance of X or Y from multi-view to iso-view, not the actual length itself.

L is orthogonal not equal to L in isometric

Isometric angles & non-iso lines

• Example of producing non-isometric lines.

• The position of point Z is obtained in the isometric view, by transferring the distance of X and Y.

Inclined Surfaces in Isometric

Inclined surfaces can not be measured along inclined lines in an isometric

sketch. To locate inclined surfaces you must make measurements along the

isometric axis lines.

Producing Isometric drawing-

Inclined Surfaces in Isometric

Circles in Isometric

• Circles appear as ellispses when

drawn in an isometric sketch.

• To sketch an

isometric circle, locate the center and then sketch the box

that would enclose

the circular shape.

Draw the ellispse tangent to the lines

of the box.

Iso-circles and arcs

• Isometric circles or iso-circle cannot be

simply drawn using compass.

• Any iso-circle may lie on either top plane, left (front) plane or right (profile) plane.

• Iso-circle looks slightly oval and skewed.

Ellipses can be in any plane

Producing isometric circle

– Draw centre lines AOB and COD, O is centre of circle, AO=OB=CO=OD = radius of circle.

– Draw FCG and EDH parallel to AOB,

draw FAE and GBH parallel to COD.

– Draw diagonal FOH, mark points J and K where FJ = HK = radius of circle.

– With centre G and rad. R1 = GA, draw an arc

between GJ produced at L and GK produced at M. Similarly with centre E.

– With centres J and K and radius R2 = JL and KM,

complete the figure.

Iso-circles and arcs:

• Drawing isometric circles and arcs using

four-centre method

Drawing iso-circles

• To draw an iso-circle,

on left plane, Diameter 20mm

(a) Draw centre lines, vertical & 30deg to left.

(b) Draw (construction line) 20mm “square box”.

The centre lines should

divide each side by half.

(c) Draw straight lines; 1-2 & 1-3 and 2-5 & 2-6.

(d) Point 7 is the intersection between line 1-2 & 2-5, and similarly point 8, 1-3 & 2-6 on the other side.

(e) Set your compass to the distance 7-2, draw an arc with centre at point 7, from point 2

to point 5. Do the same on the other side. (f) Set your compass to the distance 1-2, draw an arc with centre (1), from (2) to (3).

(a)

1 2

3

4

5

6

7

8

2

5

4

5

6

(b) (c)

(d) (e) (f)

Iso-circles and arcs:

• Drawing isometric circles using ordinate

method.

Drawing isometric circles using ordinate method.

Arcs in Isometric Sketches

Arcs are usually

sketched by

locating their

centers and

then boxing in the enclosing

parallelogram.

Sketch the arc

tangent to the

enclosing box, which is drawn

along isometric

lines.

3.3 Irregular curves in isometric • Irregular curves in

isometric are produced by transferring the coordinates from orthogonal view.

• A fixed distance is set, A, and the distance in B direction are obtained.

• These values are then transferred to the isometric view.

3.4 Producing Isometric Drawing

Producing Isometric drawing

– Read the orthogonal drawing carefully,

– observe the scale,

– choose the best point where isometric axes meet to reveal as much detail as possible

– draw an 'isometric box' enclosing the object

– draw in light construction lines

– draw arc & curves in thick, remove excess..

– line in 30 right lines

– line in 30 left lines

– line in vertical lines to complete the view


• Read multi-view dwg given.

• Observe scale, dimension, proj. angle

• Determine front, side & top view.

• Try to visualise how the object looks like.

• Start with sketching, do not draw straight away.

• If not sure, start with sketching an isometric box, enclosing the whole object.

• You can label points, lines and surfaces on multi-view to help visualisation.


• You can start drawing, once you’re able to visualise how the object looks like, or finish sketching.

• Start with drawing construction line – draw the iso-box, and fill up with other lines.

• Line in (darken) arcs & circles.

• Line in iso-lines.

• Line in all other lines.

Isometric dimensions

• Although isometric drawing is not intended

to transmit dimension, sometimes

dimensions are placed to indicate the size.

• Two types:

Hidden Lines Hidden lines are not usually

shown in isometric sketches

unless they are needed to

show a feature that would be

unclear.

Usually the orientation for

the isometric drawing should be chosen so that hidden

lines aren’t needed.

Holes are assumed to go

completely through the

object unless their depth is

indicated with a note or with

hidden lines.

Isometric features

• Common feature shown in isometric drawing.

Screw thread (external)

Fillet and rounds

Isometric section view

Isometric assembly: 3D render

Isometric exploded assembly

3.5 Oblique projection drawing

• Oblique

projection –

parallel

projection where the projectors

are parallel to

each other but not

perpendicular to the projection

plane

Oblique projection drawing

• The actual angle that the projectors make

with the plane is not fixed, but preferably

between 30deg – 60deg

• Most common 45 degree


• 3 types:

– Cavalier projection: true length along axis

– Cabinet projection: half true length

– General: any from half to full true length


• Place complex

surfaces (arcs,

holes, irregular

curve, etc.) parallel to front

plane

• The longest

dimension should be parallel to frontal plane

Producing oblique sketch

• First, sketch the front face.

• Project 45 deg line to the back.

• For holes, determine the visibility.

• Line in all object lines.

End of Topic 3 ISOMETRIC

THANK YOU

Step by Step: Isometric Sketching

Isometric Drawing Exercise


The following presentation will

demonstrate how to draw isometric

objects using the “box method”.


When drafting objects freehand, care must

be taken to draw accurately and neatly.

Therefore, all lines should be drawn as a

single line—do not shade any line.

Single line Shaded line


You will use two different lines to sketch objects:

Construction lines are light lines sketched in as you initially draw the object.

Drawing lines are dark lines which may be used for the initial drawing or which may be created by neatly darkening a construction line.


To draw an isometric

object using the

box method,

perform the

following steps:

Step 1: Draw a box

around the object

you wish to draw.


Step 2: Draw a box on your paper, in the

same proportions as the box you drew on

the object, 1½ to 2 times larger than

the original box.

Original box

Proportional box


Step 3: Look at the front side of the object. Which surface touches the outside of the box?

Step 4: Draw the surface on your box using drawing lines.


Step 5: Look at the top of the object. Which surface touches the outside of the box?

Step 6: Draw the surface on your box using drawing lines.


Step 7: Look at the right hand side of the object. Which surface touches the outside of the box? Step 8: Draw the surface on your

box using drawing lines.


Step 9: Complete

the box by drawing

in the “third lines”.

You may wish to

draw construction

lines then neatly

cover the

construction lines

with drawing lines.


To complete the Isometric Drawing Exercise,

return to the Sketching and Freehand Drawing

Fundamentals page, open up the Isometric

Drawing Exercise page and print a copy of the

exercise. Your task will be to draw nine

isometric objects freehand, using the box

method as demonstrated in this presentation.


To complete the exercise, you may divide a

piece of plain white paper (8” x 11”) into

four equal quadrants by lightly creasing the

paper in half horizontally and also in half

vertically. Each object can be sketched into

its own quadrant. You will need three pieces

of paper to complete the exercise.

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The Orthographic Views Sketch

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The Isometric Grid

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Box Object

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Choose and Map a Surface

• Identify the Principal

Surface A

A

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Map Another Surface

• Identify the Inclined

Surface B B

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• Identify Principal

Surface C

C

Map Surface

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D

Map Surface

• Identify Oblique

Surface D

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Map Surface


Surface

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Map Surface


Surface

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Map Surface


Surface

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Notch

Q: What kind of surface

has its characteristic

shape in 2 views?

Inclined Surface This surface would show up as an edge in the 3rd view

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Finished Example

Producing Isometric Sketches

• Isometric drawing starts with isometric

sketches.

• Begin with defining isometric axis.

• Begin sketch by extending axes – vertical

lines, 30deg left & right.

6.3 Producing Isometric Sketches

• Sketch an isometric ‘box’.

• Sketch the view on each faces, starting

with isometric lines.

• Add in non-iso lines and other details

• Darken all visible lines.

6.3 Iso-circles and arcs: sketch

• Sketching iso-circle is simpler than drawing.

• Create isometric square, each side=diameter.

• Find the centre point and midpoints of each side.

• Use the construction lines and point to sketch each quarter of the circle.

6.3 Sketching isometric cylinder • Start by drawing the bounding box.

• The front end of the cylinder is sketched using the previous technique.

• The far end of the cylinder is a partial iso-circle. Sketch until meeting the tangent with the two straight lines.

Lect 4 P. 85 Autumn Quarter

Sketching an Isometric of a Hollow Pipe


Step 1 - Creating the Base Box

Diameter

Diameter Length


Step 2 – Ellipse on Front Face

Lines to Tangent Points

- lines to tangent points

- corner to corner to get center

Tangent Points


Step 3 – Ellipse on Front Face

Tangent Points

Sketch in Arcs


Step 4 – Ellipse on Back Face and Profile

Draw Tangent Lines for Profile

Complete Visible Part of Back Ellipse

Repeat for ellipse on rear face


Step 5 – Ellipse for Hole on Front Face

Create Box for Hole

Sketch Ellipse

• THANK YOU FOR YOUR ATTENTION

• ANY QUESTIONS?

Isometric Drawing

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