Abbreviations and Symbols for Engineering Drawing & CNC Machining

Engineering drawing of hydraulic cylinder
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Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.

Engineering drawing abbreviations are a set of standardized symbols and abbreviations used on engineering drawings to represent common terms and phrases. The symbols and abbreviations represent various components, processes, and measurements used in engineering design. Abbreviations are used to reduce the amount of text required to convey the same information on a drawing. These abbreviations can be found on engineering drawings such as mechanical, electrical, piping and plumbing, civil, and structural drawings. Common abbreviations include AC (alternating current), DC (direct current), FAB (fabrication), and LD (load).

As an integral part of CAD/CAM technology, CNC design is used to develop and produce products. However, engineering drawings are complex as they are full of symbols and abbreviations that you might not understand. Here we provide a complete guide to standard engineering drawing abbreviations and symbols for your reference.

Why Abbreviations and Symbols Are Needed for Engineering Drawing?

Abbreviations and symbols are used in engineering drawings to save time, improve accuracy and clarity, increase standardization, simplify complex information, and reduce costs. They provide a quick and efficient way of conveying detailed information without having to write out lengthy descriptions, which helps to ensure that all parts and details are accurately specified and understood by everyone involved in the engineering project. Standardization of abbreviations and symbols across the engineering industry makes it easier to communicate between engineers and other professionals, and helps to reduce the amount of time and effort required to create engineering drawings. Its functions can be included below:

  1. To save time and space: Abbreviations and symbols are used in engineering drawings to conserve space and time. They provide a quick way of communicating information without having to write out lengthy descriptions.
  2. To improve accuracy and clarity: Abbreviations and symbols are used to ensure that all parts and details are accurately specified and understood by everyone involved in the engineering project.
  3. To increase standardization: Abbreviations and symbols are standardized across the engineering industry, which allows for more efficient communication between engineers and other professionals.
  4. To simplify complex information: Abbreviations and symbols are used to simplify complex information, making it easier for engineers and other professionals to understand what is being conveyed in the drawing.
  5. To reduce costs: Abbreviations and symbols reduce the amount of time and effort required to create engineering drawings, decreasing costs associated with a project.

How to Read Symbols in An Engineering Drawing?

Technical standards are the definition and glossary of abbreviations, symbols, and acronyms that may be found on engineering drawings. International Engineering Standards may be different from countries and applications applied, like International (ISO), USA (AISI, ANSI, ASTM, SAE, AMS), UK (BS), France (AFNOR), Germany (DIN, WR), Australia (AS), Sweden (SS), Korea (KS). Note that the same abbreviation may represent different meanings in different types.

Once you understand the meaning and definition of the symbols and abbreviations, you’ll pick up and use the engineering drawing with ease. An engineering drawing often tells the specific requirements and detail, such as:

  • Finish
  • Tolerances
  • Dimensions
  • Hardware
  • Geometry
  • Material type

Engineering Drawing Abbreviations

The charts below are a complete list of abbreviations and symbols in engineering drawings. All the lists provided below are in alphabetical order for easy reference, you can use this as a guide to help you understand your engineering drawing.


ACacross corners
AFacross flats
AFFabove finished floor
AISIAmerican Iron and Steel Institute
Al or ALaluminium
AMSAerospace Material Standards
ANNanneal, annealed
ANSIAmerican National Standards Institute
AQLacceptable quality level
ARas required
ASAerospace Standards; Australian Standards
AS, APS, APV, AV, APSL, AVLapproved product supplier, approved vendor, approved-product-supplier list, approved-vendor list
ASAAmerican Standards Association
ASMEAmerican Society of Mechanical Engineers
ASSY or ASYassembly
ASTMFormerly the American Society for Testing and Materials; now ASTM International
AWGAmerican Wire Gauge


BASICbasic dimension
BC or B.C.bolt circle
BCD or B.C.D.bolt circle diameter
BHCbolt hole circle
BHCSbutton head cap screw
BHNBrinell hardness number
BoM or BOMbill of materials
BoP or BOPbought out part
BP, B/Pblueprint
BSCbasic dimension


CADcomputer-aided design, computer-aided drafting; cadmium [plating]
CAGECommercial and Government Entity [code]
C-C or C-TO-Ccentre-to-centre; on centres
CBNcubic boron nitride
CDAcurrent design activity
CERT or certcertification
CGcenterless ground, centerless grinding
Center mark.svgCenter mark
CH or CHAMchamfer
CIcast iron
CL or ℄centreline or centerline; class
CNCcomputer numerical control
CRcontrolled radius
CREScorrosion-resistant [steel]
CRScold rolled steel; on centres
C/TCorrelation / Tracking
C’BORE or CBORE or Counterbore symbol.svgcounterbore
CSK or CSINK or Countersink symbol.svgcountersink
CTN, ctncarton


Down engineering symbol.svgdepth, deep, down
Ddiameter; delta
DIPductile iron pipe
DIMdimension, dimensioning
DO, doditto
DOD, DoD[U.S.] Department of Defense
DPDdigital product definition
DWG, dwgdrawing


EDedge distance
EO, ECO, ECNengineering order
EQL, EQequal, equally
ERCelectrical rule check


FAOfinish all over
FCFfeature control frame
FD or F/Dfield of the drawing
FIMfull indicator movement
FLflag note, flagnote
FLFloor Level
FN or F/Nflag note, flagnote; find number
FoSfeature of size
FPSOFloating Production Storage and Offloading
FSfar side
FSCMFederal Stock/Supply Code for Manufacturers


GCIgray cast iron
GD&T or GDTgeometric dimensioning and tolerancing
GN or G/Ngeneral note(s)


HBWhardness, Brinell, tungsten tip
HDPEhigh-density polyethylene
HHCShex head cap screw
HRAhardness, Rockwell, A scale
HRBhardness, Rockwell, B scale
HRChardness, Rockwell, C scale
HRShot rolled steel
HT TRheat treat, heat treatment
H&T or H/T or HThardened and tempered


IAWin accordance with
IDinner diameter; identity, identification number
IEDInsufficient Edge Distance
ISOInternational Organization for Standardization


JISJapan Industrial Standard


KPSI, kpsikilopounds per square inch, that is, thousands of pounds per square inch
KSI, ksikilopounds per square inch, that is, thousands of pounds per square inch


LDDlimited dimension drawing
LM or L/Mlist of materials
LMCleast material condition


MACHmachine; machined
MBDmodel-based definition
MBPmeasurement between pins
MBWmeasurement between wires
MF or M/Fmake from
MIL-[U.S.] Military
MINminimum; minutes; minor
MMCmaximum material condition
MOD, MoDMinistry of Defence [U.K. and others]
MOP, MoPmeasurement over pins
MOW, MoWmeasurement over wires
MPa, MPAmegapascals
MRBmaterial review board
MS-[U.S.] Military Standard


NASNational Aerospace Standards
NCNational Coarse; numerical control
NCMnonconforming material(s)
NCRnonconformance report
NECnot elsewhere classified; National Electrical Code
NEFNational Extra Fine
NFNational Fine
NL or N/Lnotes list
NORM or NORMDnormalized
NPSNaval Primary Standard[3]
NPTNational Pipe Taper
NSNational Special; near side
NSCMNational Stock/Supply Code for Manufacturers
N&T or N/T or NTnormalized and tempered
NTSnot to scale


OALoverall length
OCon center(s)
ODouter diameter
ODAoriginal design activity
OHLover high limit


pc, pcspiece, pieces
PDpitch diameter
PDM, PDMSproduct data management, product data manager [app], product data management system [app]
PH or P/Hprecipitation hardening, precipitation-hardened; pilot hole
PHR BRZphosphor bronze
PL or P/Lparts list
PLMproduct lifecycle management; plant lifecycle management
PMIProduct and manufacturing information
PN or P/Npart number
POIpoint of intersection fit
PSIpounds per square inch
PVCpolyvinyl chloride


QMSquality management system
QTY or qtyquantity


RA, Raroughness, average; Rockwell A scale
RB, RbRockwell B scale
RC, RcRockwell C scale
REFreference dimension
REQD or REQ’Drequired
RFSregardless of feature size
RHRroughness height reading
RLReduced Level or Relative Level
RMAreturn material authorization
RMSroot mean square
RT or R/Trough turn, rough turned; room temperature
RTPrelease to production
RTVroom-temperature vulcanizing; return to vendor
RZ, Rzroughness, mean depth


SAEFormerly the Society of Automotive Engineers; now SAE International
SC or S/Csharp corners
SF or S/Fspotfaceslip fit
SFACE or S/FACEspotface
SHCSsocket head cap screw
SHSSsocket head set screw
SISystème international [d’unités] [International System of Units]
SN or S/Nserial number
SOL ANNsolution anneal, solution annealed
SPEC or specspecification
SPHER ANNspheroidize anneal
SPOTFACESpot facing
SRspherical radius
SS or S/Sstainless steel; supersede
SSTstainless steel
STEPStandard for the Exchange of Product Model Data
STAsolution treated and aged
STIscrew thread insert


TAPtapped hole
TB or T/Btitle block
TCCtime-current curve
TDPtechnical data package
THD or thdthread
THK or thkthickness
THRU ALLThrough all
TIRtotal indicator reading; total indicated run-out
TOStop of steel
TOLtolerance, tolerancing
TSCtheoretical sharp corner(s)


UAIuse as-is
ULLunder low limit
UNCUnified National Coarse
UNEFUnified National Extra Fine
UNFUnified National Fine
UNJCUnified National “J” series Coarse
UNJFUnified National “J” series Fine
UNOunless noted otherwise
UNSUnified National Special; unified numbering system
UONunless otherwise noted
UOSunless otherwise specified
USASIUnited States of America Standards Institute
USSUnited States Standard; United States Steel
UTSultimate tensile strength; Unified Thread Standard




WCtungsten carbide
WIwrought iron
W/I, w/iwithin
W/O, w/owithout


_X_used to indicate the word “by”
X or ( )number of places—for example, 8X or (8)


YSyield strength

Common Engineering Drawing Abbreviations Used in CNC Machining

Although it’s easy to illustrate all the details in a design drawing for the manufacture of CNC milling parts or CNC turning parts, there is not enough space on a drawing to cover all the texts and images. The abbreviations and symbols are then designed to express the characteristics of the product. They are easy to be understood by people from any country in concise forms. Common engineering drawing abbreviations used for CNC machining are listed below:

ACAcross corners
AQLAcceptable quality level
ARAs required
BASIC or BSCBasic dimension
BC or B.C.Bolt circle
BHCBolt hole circle
CADComputer-aided design
CICast iron
CNCComputer Numerical Control
EDEdge distance
IAWIn accordance with
LMCLeast material condition
MBPMeasurement between pins
MBWMeasurement between wires
MMCMaximum material condition
OALOverall length
PDPitch diameter
PLParts list
PMIProduct and manufacturing information
RZRoughness, mean depth
SNSerial number
UNCUnified National Coarse
UNSUnified National Special
YSYield Strength

Engineering Drawing Symbols

The basic symbol types used in engineering drawings are diameter, depth, radius, counterbore, spotface, and countersink. The following are commonly used engineering drawing symbols and design elements.

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