• There are many, many, symbols and abbreviations that are used in engineering

• Their purpose is to simplify the production process

• By looking at a symbol you can tell a great deal of things, from the material type, to the

projection that the drawing is done from

• The American Standards Association issued the first American standards (1935), entitled

“Drawing and Drafting Room Practices”

• BSI (British Standards Institution: 308) set guidelines, the first part published in 1984, the

second in 1985, and then third 1990. These lay the standard out for our country

• ISO (International Standard Organisation), these standards are agreed on internationally

• BSI revisions are being updated progressively so that they should be in line with the ISO

standard

• Lines in drawings have various meanings, this makes it easy to look at the drawing and

immediately pick up information

• Thick lines are approximately 6mm, and thin lines are 3mm

• First UK/EU convention

• Start from a plan view (above) located at the bottom of the

page, that is “folded” over to show a side view, and flipped

again either side to show front and rear views

• Third US convention

• Start from a plan view (above) located at the top of the page,

that is “swung” down to show the side view, and flipped again

either side to show front and rear views

• There are hundreds of abbreviations

• A small list of some is shown here on the right

• Abbreviations save you having to write the whole word out

• Having abbreviations saves space that can be better utilised by

the drawing

• There are hundreds of abbreviations, and which ones are used

are the drawers responsibility

Term Abbreviations Term Abbreviations

Across Corner A/C Material MATL

Across Flat A/F Mechanical MECH

Approved APPD Number No.

Approximate APPROX Not to Scale NTS

Assembly ASSY Outside Diameter OD

British Standard

FineBSF Pitch Circle PC

British Standard

WitworthBSW Right Hand RH

Cast Iron CI Rivet RVT

Cast Steel CS Reference REF

Case Hardened CH Screw SCR

Centre line CL Sheet SH

Chamfered CHMED Serial Number Sl. No.

Countersunk CSK Standard STD

Counter Bore C’BORE Spot face SF

Cylinder CYL Specification SPEC

Diameter DIA Spherical SPHERE

Drawing DRG Square SQ

Dimension DIM Symmetrical SYM

Extruded EXTD True Position TP

External EXT Traced TCD

Figure FIG Unified Fine UNF

Hydraulic HYD Round RD

Hexagonal HEX Undercut U/Cut

Horizontal HORZ

Indian Standard IS Beam

Inside diameter ID Channel

Internal INTNumber of

teeth (Gear)

Machine M/C Parallel

Machined M/CDTee (Structural

section)

• Materials are classified numerically, with the IADS defining the Aluminium standards, and

AISI/SAE being used for steel

• Both systems are similar in function

• These codes have meanings, and can be read easily by someone who understands the

convention

• This saves a very large amount of space that can be otherwise used by the drawing of the

work at hand

• For example;

• An Aluminium alloy with the code 7075 is an alloy of Aluminium which contains Zinc,

has no impurity control, and has at least 99.75% aluminium

• A Steel alloy with the code 1020 is an alloy of Steel which contains only carbon, and

no other alloying elements, carbon content is approx 0.2%

• They are coded using the the International Alloy Designation System (IADS) standard

• The digit "1" as in 1xxx designates alloy free (no alloys) and is at least 99% Aluminium.

• The Digit is interchangeable, and depending on it’s value, it means there is a different

alloy that is also within the aluminium, some contain multiple major alloys, they are as

follows:

• “2” for Copper (Cu), “3” for Manganese (Mn), “4” for Silicon (Si), “5” for Magnesium, “6” for

Magnesium and Silicon (Mg and Si), “7” for Zinc (Zn), “8” for an unspecified alloy

(including Lithium [Li])

• The second part x0xx denotes the purity control of the Aluminium, where “0” is no control,

and “1-9” are different controls set at the mill, these levels are set by AIDS

• The final part is the minimum Aluminium percentage above 99%. So xx25 means “99.25%

minimum Aluminium content”

• Similar to IADS, but slightly different in that the first two digits denote the elements that

are found within, and the last two is the percentage content above “0” of carbon

• Known as AISI/SAE

10XX

Carbon steels

Plain carbon, Mn 1.00% max

11XX Resulfurized free machining

12XXResulfurized / rephosphorized free

machining

15XX Plain carbon, Mn 1.00-1.65%

13XX Manganese steel Mn 1.75%

23XXNickel steels

Ni 3.50%

25XX Ni 5.00%

31XX

Nickel-chromium steels

Ni 1.25%, Cr 0.65-0.80%

32XX Ni 1.75%, Cr 1.07%

33XX Ni 3.50%, Cr 1.50-1.57%

34XX Ni 3.00%, Cr 0.77%

40XXMolybdenum steels

Mo 0.20-0.25%

44XX Mo 0.40-0.52%

41XX Chromium-molybdenum steels Cr 0.50-0.95%, Mo 0.12-0.30%

43XXNickel-chromium-molybdenum

steels

Ni 1.82%, Cr 0.50-0.80%, Mo

0.25%

47XXNi 1.05%, Cr 0.45%, Mo 0.20-

0.35%

46XXNickel-molybdenum steels

Ni 0.85-1.82%, Mo 0.20-0.25%

48XX Ni 3.50%, Mo 0.25%

50XX

Chromium steels

Cr 0.27-0.65%

51XX Cr 0.80-1.05%

50XXX Cr 0.50%, C 1.00% min

51XXX Cr 1.02%, C 1.00% min

52XXX Cr 1.45%, C 1.00% min

61XX Chromium-vanadium steels Cr 0.60-0.95%, V 0.10-0.15%

72XX Tungsten-chromium steels W 1.75%, Cr 0.75%

81XX

Nickel-chromium-molybdenum

steels

Ni .30%, Cr 0.40%, Mo 0.12%

86XX Ni .55%, Cr 0.50%, Mo 0.20%

87XX Ni .55%, Cr 0.50%, Mo 0.25%

88XX Ni .55%, Cr 0.50%, Mo 0.35%

92XX Silicon-manganese steelsSi 1.40-2.00%, Mn 0.65-0.85%,

Cr 0-0.65%

93XX

Nickel-chromium-molybdenum

steels

Ni 3.25%, Cr 1.20%, Mo 0.12%

94XX Ni 0.45%, Cr 0.40%, Mo 0.12%

97XX Ni 0.55%, Cr 0.20%, Mo 0.20%

98XX Ni 1.00%, Cr 0.80%, Mo 0.25%