Engineering drawings are technical diagrams and representations meant to define parameters and other plans for something that is to be engineered. This is also known as drafting, and can be used in the fields of civil engineering, architecture, carpentry, landscaping, and so on. Technical drawings are much more than just simple diagrams, though – it is its own language with a set of conventions, including symbols and other markings used to designate specifics.

If you’re studying engineering and need a reference sheet for these drafting symbols, you’ve come to the right place. This guide will list some of the need-to-know drafting symbols, and provide some resources for your studies. Not sure where to start? Check out this course on finding a career in engineering to see if it’s right for you.

List of Drafting Symbols

Below, you’ll find our list of drafting symbols in alphabetical order. You might also want to check out this guide to learning AutoCAD, or take a crash course in Autodesk AutoCAD for a more in-depth approach to drafting and engineering.

A

• AC – “across corners”
• AF – “across flats”
• AS – “Aerospace Standards” – technical standards used in the industry of aerospace manufacturing. You can learn the project management process that meets these requirements in this course.

B

• BC – “bolt circle”
• BoM or BOM – “bill of materials”
• BSC (or BASIC) – “basic dimension”

C

• CAD – “computer aided design”
• CR – “controlled radius”
• CBORE – “counterbore” – represented with a symbol resembling the lower half of a square:┗┛

Master AutoCAD with this AutoCAD tutorial course. Or, check out this course on Autodesk Revit Architecture 2014 essentials.

D

• DIA – “diameter” – represents the diameter of a circle: ⌀
• DIM – “dimension”
• DPD – “digital product definition”

You’ll find a lot of geometry in architecture and engineering. Check out this beginner’s course to geometry for an introduction.

E

• EO, ECO, ECN – “engineering order” – designates an order directly from the engineering department, which the department of production should follow regardless of whether or not it contradicts another – the engineer order should override
• EQ – “equal”

F

• f – “finish”
• FS – “far side” – used in conjunction with the drafting symbol for “near side,” which tells the engineer which side something is on
• FSCM – “Federal Stock/Supply Code for Manufacturers” – also referred to as the CAGE code

G

• GD&T, GDT – “geometric dimensioning and tolerancing” – defines dimensions and tolerances according to standardized definitions
• GN – “general notes”

H

• HRA – “hardness Rockwell A scale”
• HRB – “hardness Rockwell B scale”
• HRC – “hardness Rockwell C scale”

These three symbols represent hardness according to the Rockwell scale, a scale that measures indentation hardness for materials. In what kind of engineering job would you need to know this? Consult this guide to the various types of engineering jobs and learn what you need to know for each, then find the right engineering job for you with this guide.

I

• IAW – “in accordance with” – used to denote what kind of technical standard an instruction should be carried out under
• ID – “inner diameter” or “identification number” – contextual
• ISO – “International Organization for Standardization”

K

• KEY – “key” – means exactly that; a way to highlight key characteristics of a project that have some kind of importance in regards to functionality, safety, or aesthetics
• KPSI – “kilopounds per square inch”

L

• LM – “list of materials” – a list of parts required for assembly, also called a “parts list” or a “bill of materials” and referenced as PL or BoM, respectively

M

• MACH – “machined”
• MAX – “maximum”
• MF – “make from” – can be used in a list of materials to indicate if one part should be engineered with additions to create a second part
• MIN – “minimum”
• MS – “U.S. military standard” – used to denote standards of the United States military in regards to defense industries and aerospace manufacturing

N

• NAS – “National Aerospace Standards”
• NCM – “non-conforming material(s)”
• NEC – “not elsewhere classified”
• NOM – “nominal”
• NTS – “not to scale”

O

• OAL – “overall length”
• OD – “outer diameter”
• OHL – “over high limit”

P

• pc, pcs – “pieces” or “pieces”
• PDM – “project data management”
• PL – “parts list”
• PSI – “pounds per square inch”
• PTFE – “polytetrafluoroethylene” – the synthetic compound known as Teflon, a popular brand name

Q

• QMS – “quality management system”
• QTY – “quantity”

R

• R – “radius” – Need more geometry help? Don’t pass up this introductory geometry course.
• REQ, REQ’D – “required”
• REV – “revision” – must be used to denote a revision on an engineering drawing, following the standards of revision control and maintaining various versions in the revision block, and what has changed between them
• RFS – “regardless of feature size”
• RMS – “root mean square”
• RTP – “release to production” – the symbol that marks an engineering drawing as complete, and ready to be handed over officially to the production department; usually the document will be stamped with the words “ISSUED” to make it official

S

• SC – “sharp corners”
• SN – “serial number”
• SPEC – “specification”
• SST – “stainless steel”
• STD – “standard”
• STEP – “Standard for the Exchange of Product Model Data”
• STL – “steel”
• STK – “stock”

Learn some AutoCAD 2014 drawing essentials in this course on the engineering software.

T

• TB – “title block” – a sectioned off block of the engineering drawing, usually in the bottom right hand corner, that indicates important information about the drawing such as title, drawing number, ID and patent numbers, and so on.
• TDP – “technical data package”
• THRU ALL – “through all”

Learn tips and tricks for modeling and rendering in AutoCAD with this course on AutoCAD 3D.

U

• UAI – “use as is”
• ULL – “under low limit”
• UON – “unless otherwise noted” – this one isn’t used often so it is best to spell it out entirely
• UOS – “unless otherwise specified” – see above
• USS – “United States of America Standards Institute”

V

• v – “finish” – when written over a line representing a surface, an italicized and lowercase “v” indicates that the marked surface should be machined

W

• WI – “wrought iron”
• W/I – “within”
• W/O – “without”

Y

• YS – “yield strength”

Abstract Symbols

⏤ – form, straightness

○ – form, circularity

⌭ – form, cylindricity

⌒ – profile, line

⌓ – profile, surface

∠ – orientation, angularity

∥ – orientation, parallelism

⌯ – location, symmetry

⌖ – location, positional tolerance

◎ – location, concentricity

↗ – run-out, circular

⌰ – run-out, total

Check out this course on AutoCAD 2014 editing essentials for more drawing, drafting, and editing tips.