Scale used in geometric construction

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Division of lines

Figure 7.16 shows the method of dividing a given line AB, 89 mm long, into a number of parts (say 7).

Draw line AC, and measure 7 equal divisions. Draw line B7, and with the tee-square and set-square draw lines parallel to line B7 through points 1 to 6, to give the required divisions on AB.

Scale rule

Scale rule

2770 mm

100 80 60 40 20

100 80 60 40 20

500 mm

1000 mm

500 mm

1000

2000

3000

Fig. 7.18 Diagonal scale where 40 mm represents 1000 mm

Figure 7.16 shows the method of dividing a given line AB, 89 mm long, into a number of parts (say 7).

Draw line AC, and measure 7 equal divisions. Draw line B7, and with the tee-square and set-square draw lines parallel to line B7 through points 1 to 6, to give the required divisions on AB.

Geometric Construction Drawing
7C

Figure 7.17 shows an alternative method.

1 Draw vertical lines from A and B.

2 Place the scale rule across the vertical lines so that seven equal divisions are obtained and marked.

3 Draw vertical lines up from points 2 to 7 to intersect AB.

Diagonal scales

Figure 7.18 shows the method of drawing a diagonal scale of 40 mm to 1000 which can be read by 10 mm to 4000. Diagonal scales are so called since diagonals are drawn in the rectangular part at the left-hand end of the scale. The diagonals produce a series of similar triangles.

1 Draw a line 160 mm long.

2 Divide the line into four equal parts.

3 Draw 10 vertical divisions as shown and to any reasonable scale (say 5 mm) and add diagonals.

An example of reading the scale is given. Plain scales

The method of drawing a plain scale is shown in Fig. 7.19. The example is for a plain scale of 30 mm to 500 mm to read by 125 mm to 2500.

500 mm

500 mm

Least Material Condition Example

2000

Fig. 7.19 Plain scale where 30 mm represents 500 mm

2000

Fig. 7.19 Plain scale where 30 mm represents 500 mm

1 Draw a line 150 mm long and divide it into 5 equal parts.

2 Divide the first 30 mm length into four equal parts, and note the zero position or, the solution.

An example of a typical reading is given.

This method of calibration is

in common use in

Least material condition:

industry, and scales can be obtained suitable for a variety

(a) In a note

LMC

of scale ratios.

(b) Part of a geometrical tolerance

L

Long

Machine

LH LG MC

Abbreviations

Maximum material condition: (a) In a note

MATL MAX

MMC

In order to shorten drawing notes we often use

(b) Part of geometrical tolerance

M

abbreviations, and the following list gives a selection

Minimum

MIN

of commonly used terms in accordance with BS 8888.

Not to scale (in a note and underlined)

NTS

Number

NO.

Pattern number

PATT NO.

Term

Abbreviation or symbol BS 8888

Pitch circle diameter Radius:

(a) In a note

PCD RAD

Across flats

A/F

(b) Preceding a dimension

R

Assembly

ASSY

Reference

REF

Centres

CRS

Required

REQD

Centre line:

Right hand

RH

(a) on a view and across a centre line

<L

Round head

RD HD

(b) in a note

CL

Screw or screwed

SCR

Centre of gravity

CG

Sheet (referring to a drawing sheet)

SH

Chamfer or chamfered (in a note)

CHAM

Sketch (prefix to a drawing number)

SK

Cheese head

CH HD

Specification

SPEC

Countersunk/countersink

CSK

Spherical diameter (only preceding

Countersunk head

CSK HD

a dimension)

S0

Counterbore

CBORE

Spherical radius (only preceding

Cylinder or cylindrical

CYL

a dimension)

SR

Diameter:

Spotface

SFACE

(a) In a note

DIA

Square:

(b) Preceding a dimension

0

(a) In a note

SQ

Dimension

DIM

(b) Preceding a dimension

□ or B

Drawing

DRG

Standard

STD

Equally spaced

EQUI SP

Taper (on diameter or width)

External

EXT

Thread

THD

Figure

FIG

Thick

THK

Full indicated movement

FIM

Tolerance

TOL

Hexagon

HEX

Typical or typically

TYP

Hexagon head

HEX HD

Undercut

UCUT

Insulated or insulation

INSUL

Volume

VOL

Internal

INT

Weight

WT

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Responses

  • stephan baum
    What is geometric scale in ed?
    2 years ago
  • Camilla Rizzo
    How to draw eclipse in EG and diagonal scale?
    2 years ago
  • juuso
    What is a plain scale rule?
    2 years ago
  • KYLLIKKI
    What is the constraction drowing scales?
    2 years ago
  • Aki-Petter Huuskonen
    How can you draw division of line in technical drawing?
    2 years ago
  • artemisia
    Where do we use scale rule to draw in a plain scale?
    2 years ago
  • Lino Zito
    How to draw plain scale using different pencils?
    1 year ago

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