StandardsThe British Standard for weld symbols is BS EN 22553. When identification of the weld process is required as part of the weld symbol the relevant weld process code is listed in BS EN ISO 4063.

Basic Weld SymbolThe weld symbol always includes

1. An arrow line

2. A reference line

3. A dashed line

4. A symbol

Note: Weld symbols on the full reference line relates to welds on the near side of the plate being welded. Weld symbols on the dashed line relates to weld on the far side of the plate. If the welds are symmetrical on both sides of the plate the dashed line is omitted. If the dashed line is above the full line then the symbol for the nearside weld is drawn below the reference line and the symbol for the farside weld is above the dashed line. For example see sketch below Supplemetary symbols below.

More Detailed Symbolic Representation of Weld

Welding.....Weld process numbers.

Table of Weld Symbols

SupplementarySymbolsThe weld symbols below are used in addition to the primary weld symbols as shown above. They are not used on their own.

Below is an example of the application of one of these symbol illustrating the identification of the location of the weld relative to the symbol.

Complementary Indication

Dimensioning Welds

Dimensioning

Linear Dimensioning

Note: A dimension which is not to scale is shown underlined

Angular Dimensioning

Chain-Parallel dimensioning

Examples of chain and parallel dimensioning are shwon above. The advantage of parallel dimensioning is that there is no build-up of tolerances.

Dimensioning a brokent feature.

Dimensioning Diameters

Dimensions of diameters are shown on view providing greatest clarity

Dimensioning Holes

Dimensioning Chamfers/Countersinks

Metric Screw Threads

Thread Designation

The complete designation of a screw thread gives

the thread symbol e.g. M for Metric

the thread size e.g. 6

the thread pitch e.g. x 1

the tolerance class e.g. 6H(Female) 6g (male)

the length of thread if not dimensioned separately eg. x 30 LNG

Notes:If the thread is standard course then the pitch need not be shown. However it is better that it is always shownIf the tolerance grade for the pitch diameter and the major diameter is the same then only one needs to be shown.Threads right handed (clockwise turn to screw in) unless a -LH suffix is added to indicate left hand thread.

The Class of Fit is a measure of the degree of fit between mating internal and external threads.

Classes of Fit

Three main Classes of Fit are defined for metric screw threads :

FINE: This has a tolerance class of 5H for internal threads and 4h for external threads.

MEDIUM: This has a tolerance class of 6H for internal threads and 6g for external threads.

COARSE: This has a tolerance class of 7H for internal threads and 8g for external threads.

If one class is shown for a male thread i.e 6g then the tolerance applies to the pitch dia and the major diameter.A dual tolerance is shown (5h6g) when a different tolerance is applied to the Pitch dia (5h) and the major dia (6h). The same principle applies to the female thread e.g. a tolerance grade (6H ) applies to both pitch dia and the minor dia. A tolerance grade (6H7H) refers to 6H for the pitch dia and 7H for the minor dia.

The typical designation for a thread on a drawing is as follows

M8 - 6e..This is a M8 course male thread with a 6e external(male) tolerance (before coating)

M8 x 1 - 6e.. This is a M8 course male fine thread with a 6e external(male) tolerance (before coating)

M8 - 6H... This is a M8 course female thread with a 6H internal(female) tolerance (not coated)

M8 - 6H - LH This is a Left hand M8 course female thread with a 6H internal(female) tolerance (not coated)

Pipe Threads

The typical designation for a Pipe Threads

R 1/2 External Taper - Sealing on Thread (BS 21)

Rc 1/2 Internal Tape - Sealing on Thread(BS 21)

Rp 1/2 Internal Parallel- Sealing on Thread (BS 21)

G 1/2 A,B or ext External Parallel - Not Sealing on Threads -Additional seal required(BS2779)

G 1/2(F = full thread) Internal Parallel Not Sealing on Threads -Additional seal required (BS2779)

TermAbbreviation or Symbol

Across FlatsAF

AssemblyASSY

CentresCRS

Centre Line ..On View

Centre line ..On NoteCL

Centre Of GravityCG

Chamfer of Chamferred..In a NoteCHAM

Cheese HeadCH HD

Countersunk/ CountersinkCSK

Countersunk HeadCSK HD

CounterboreCBORE

Cylinder or CylindericalCYL

Diameter..in a noteDIA

Diameter..preceding a dimension

DrawingDRG

Equally SpacedEQUI SP

ExternalEXT

FigureFIG

Full Indicated MovementFIM

HexagonHEX

Hexagon HeadHEX HD

Insulated or InsulationINSUL

InternalINT

Least Material Condition..In a NoteLMC

Least Material Condition..(Geom.Dim)

Left handLH

LongLG

MachineMC

MaterialMAT

MaximumMAX

Maximum Material Condition..In a noteMMC

Maximum Material Condition..(Geom. tol)

MinimumMIN

Not to Scale (In a note and underlinedNTS

NumberNO.

Pattern NumberPATT NO.

Pitch Circle DiameterPCD

Radius..In a noteRAD

Radius..Preceding a dimensionR

ReferenceREF

RequiredREQD

Right handRH

Round HeadRD HD

Screw of ScrewedSCR

Sheet (Drawing Number) SH

Sketch (prefix to Drawing Number) SK

SpecificationSPEC

Spherical Radius..Preceding dim SR

SpotfaceSFACE

Square ..In a noteSQ

Square ..Preceding dim

StandardSTD

Taper.. On Dia or Width

ThreadTHD

ThickTHK

ToleranceTOL

Typically OR TypicalTYP

UndercutUCUT

VolumeVOL

General Notes

Fabrication Notes

Machining Notes

Fastener Notes