The Colored Pencil Course
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.
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.
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
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: |
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 |
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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