Symbols and abbreviations

2. • 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

3. • 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

4. • 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

5. • 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
Fine
BSF Pitch Circle PC
British Standard
Witworth
BSW 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 INT
Number of
teeth (Gear)
Machine M/C Parallel
Machined M/CD
Tee (Structural
section)

6. • 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%

7. • 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”

8. • 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
12XX
Resulfurized / rephosphorized free
machining
15XX Plain carbon, Mn 1.00-1.65%
13XX Manganese steel Mn 1.75%
23XX
Nickel 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%
40XX
Molybdenum 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%
43XX
Nickel-chromium-molybdenum
steels
Ni 1.82%, Cr 0.50-0.80%, Mo
0.25%
47XX
Ni 1.05%, Cr 0.45%, Mo 0.20-
0.35%
46XX
Nickel-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 steels
Si 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%