Basic requirements for dimensioning Dimensioning of basic body, cutting and interpenetration bodies

Dimensioning general composite solids

Exercises

Dimensioning Composite Solids

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ReasonablenessReasonableness::The dimensions must be marked according to the requirements of The dimensions must be marked according to the requirements of design, manufacture and test.design, manufacture and test.

Basic requirements for dimensioningBasic requirements for dimensioning

CorrectnessCorrectness:: There should be no mistake with all dimensions and the national There should be no mistake with all dimensions and the national standard (GB) should be observed. standard (GB) should be observed.

CorrectnessCorrectness ，， integrityintegrity ，， clarityclarity ， ， reasonableness.reasonableness.

IntegrityIntegrity : : The dimension must fully define the size of the part and the relativeThe dimension must fully define the size of the part and the relative locations of individual components. It can not be skipped, nor repeated.locations of individual components. It can not be skipped, nor repeated.

ClarityClarity :: The arrangement of the dimensions should be clear and clean.The arrangement of the dimensions should be clear and clean.

1. Basic requirements for dimensioning1. Basic requirements for dimensioning

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4)4) Each dimension of the part should mark on the drawing only once. It should also Each dimension of the part should mark on the drawing only once. It should also be marked on a drawing that most clearly represents the corresponding constructs.be marked on a drawing that most clearly represents the corresponding constructs.

1)1) The true size of the spare part is based on the dimension marked on the drawing The true size of the spare part is based on the dimension marked on the drawing and has nothing to do with the size of the drawing and the accuracy of the drawings.and has nothing to do with the size of the drawing and the accuracy of the drawings.

2) There is no need to mark the unit of dimensions if it is “mm”. One only needs to 2) There is no need to mark the unit of dimensions if it is “mm”. One only needs to mark the dimensions if the units are not “mm”, such as “cm” or “mark the dimensions if the units are not “mm”, such as “cm” or “30º30º”.”.

Basic requirements for dimensioningBasic requirements for dimensioning2. Basic rules of dimensioning2. Basic rules of dimensioning

3)3) All dimensions marked on the drawing are dimensions of the final part. OtherwiseAll dimensions marked on the drawing are dimensions of the final part. Otherwise one needs to clearly indicate on the drawing.one needs to clearly indicate on the drawing.

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3.Dimension constructionDimension construction

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② ② Dimension line is usually drawn perpendicular to the Dimension line is usually drawn perpendicular to the extension lines and the extension lines should extend extension lines and the extension lines should extend beyond the terminal of dimension line for about 2beyond the terminal of dimension line for about 2 －－ 3mm. 3mm.

23mm 7

1b

4b

44

28

44

30

Extension line

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28

99

9

9

9

9

①① An extension line is drawn with a continuous thin line. An extensionAn extension line is drawn with a continuous thin line. An extension line originates from a feature outline, an axis line, or a center line.line originates from a feature outline, an axis line, or a center line.

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Basic requirements for dimensioningBasic requirements for dimensioning

Dimension Dimension line and its line and its terminalsterminals

① ① It must be drawn using continuous thin line and can not be in It must be drawn using continuous thin line and can not be in coincident with any existing lines or drawn as extension of any coincident with any existing lines or drawn as extension of any lines.lines.②② The dimension line must be parallel with line segment being The dimension line must be parallel with line segment being dimensioned. The distance between the dimension line and the dimensioned. The distance between the dimension line and the nearest feature should be about 8nearest feature should be about 8 －－ 10mm. All distances between 10mm. All distances between neighboring dimension lines should be as consistent as possibleneighboring dimension lines should be as consistent as possible and are usually between 6and are usually between 6 －－ 8mm.8mm.

③ ③ Arrowhead is equal to 1b thick and 4b length. Arrowhead is equal to 1b thick and 4b length. （（ b=the continuous thick lineb=the continuous thick line ））

Dimension text

Φ18

3822

① ① Dimension text should be marked above or left the dimension line. Dimension text should be marked above or left the dimension line. All linear dimensions should be marked heading upwards for horizontal All linear dimensions should be marked heading upwards for horizontal dimensions, heading towards the left for vertical dimensions.dimensions, heading towards the left for vertical dimensions.

② ② Dimension text can also be entered in the breaking space of the Dimension text can also be entered in the breaking space of the dimensiondimension line.line.

③ ③ When there is When there is 3030 for horizontal line, dimension text can also be for horizontal line, dimension text can also be placed somewhere else using a leader line.placed somewhere else using a leader line.

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Orientation of linear dimensions

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One usually needs to mark all dimensions of length, width and height. One usually needs to mark all dimensions of length, width and height. For body of revolution, it only needs to mark its radial dimension (the For body of revolution, it only needs to mark its radial dimension (the diameter symbol “diameter symbol “” is added before the dimension figure) and axial ” is added before the dimension figure) and axial dimension.dimension.

1. Dimensioning the basic part1. Dimensioning the basic part

Dimensioning of basic body,cutting and interpenetration bodiesDimensioning of basic body,cutting and interpenetration bodies

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Dimensioning of basic body,cutting and interpenetration bodiesDimensioning of basic body,cutting and interpenetration bodies2. Dimensioning of subtraction/cutting type solid2. Dimensioning of subtraction/cutting type solid

When dimensioning cutting type composite solid, there are also dimensions When dimensioning cutting type composite solid, there are also dimensions for defining location of individual shape elements, such as cutting planes, in for defining location of individual shape elements, such as cutting planes, in addition to the above shape dimensions. As the intersection curve is uniquely addition to the above shape dimensions. As the intersection curve is uniquely defined with basic shape dimensions and location dimensions, there is no need defined with basic shape dimensions and location dimensions, there is no need to dimension intersection curves.to dimension intersection curves.

intersection curveintersection curve

intersection curveintersection curve

location of cutting planeslocation of cutting planes

location of cutting planeslocation of cutting planeslocation of cutting planeslocation of cutting planesintersection curveintersection curve

location of cutting planeslocation of cutting planes

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Dimensioning of basic body,cutting and interpenetration bodiesDimensioning of basic body,cutting and interpenetration bodies

3. Dimensioning of union/interpenetration type part3. Dimensioning of union/interpenetration type part

There are also location dimensions in addition to shape dimensions for There are also location dimensions in addition to shape dimensions for union/interpenetration type parts. With shape and location dimensions, the union/interpenetration type parts. With shape and location dimensions, the interpenetration curves are uniquely defined, and there is no need either to interpenetration curves are uniquely defined, and there is no need either to dimension interpenetration lines.dimension interpenetration lines.

interpenetration lineinterpenetration line

R

location dimensionslocation dimensions location dimensionslocation dimensions

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Dimensioning of basic body,cutting and interpenetration bodiesDimensioning of basic body,cutting and interpenetration bodies

4. Dimensioning of supporting board elements4. Dimensioning of supporting board elements All center-to-center spacing of holes, screw threads and grooves on the All center-to-center spacing of holes, screw threads and grooves on the

board should be dimensioned. Since the basic shape of the board and the board should be dimensioned. Since the basic shape of the board and the distribution of holes and grooves are different, the formats of location distribution of holes and grooves are different, the formats of location dimensions for dimensioning center-to-center spacing are also different.dimensions for dimensioning center-to-center spacing are also different.

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Dimensioning general composite solidsDimensioning general composite solids 1.Selection of dimension datumSelection of dimension datum

There should be at least one dimension datum for each of the three principal directions for length, width and height of the composite solid.

Length datum（ X ）

Height datum（ Z ） Width datum

（ Y ）

（ 1 ） Dimension datumDimension datum Dimension datum indicates common starting position of related dimensions.

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1 ） Datum face

error

（ 2 ） Commonly datum of dimensioningCommonly datum of dimensioning Dimensioning general composite solidsDimensioning general composite solids

Height datum ： Symmetry plane or the bottom surface. Symmetry plane or the bottom surface.

Length datum ： Symmetry plane or the end surface.Symmetry plane or the end surface.

Width datum ： Symmetry plane or back-end surface. Symmetry plane or back-end surface.

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Coordinates origin

曲面轮廓不能作为尺寸基准intersection intersection curvecurveintersection intersection curvecurveCenter line

3) Datum mark

Center point

Dimensioning general composite solidsDimensioning general composite solids

Center axes

2) Datum line

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√

×

a

b c

a b c c b

Chain dimensioning a b c

Combined dimensioning a b c

a （ 3 ） Form of commonly dimensioningForm of commonly dimensioning

×Parallel dimensioning a b c

Dimensioning general composite solidsDimensioning general composite solids

Avoidance of dimensions into a series with an overall dimensions！

Combined dimensioning is suitable

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Dimensioning general composite solidsDimensioning general composite solids

2.2.CorrectnessCorrectness and integrity in dimensioningand integrity in dimensioning

(2) Location dimensions show the relative location relationships between individual shape elements.

(3) Overall dimensions show the overall length, width and height of the composite solid.

(1) Shape dimensions show sizes, such as length, width and height, of the basic part and its building elements.

Center of holes Center of holes must be given must be given clearlyclearly

Over-dimensionedOver-dimensioned (10)

Overall length Overall length added as an added as an auxiliaryauxiliary

R

Overall length must Overall length must be given clearlybe given clearly

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Dimensioning general composite solidsDimensioning general composite solids

3.3.ClarityClarity and reasonableness in dimensioningand reasonableness in dimensioning(1) Dimensions should be marked in the view that most reflects the

characteristics of the related shape and location.

R

Φ

R

R

extendR

Marked in Marked in bevelbevel

Marked inMarked in bulgebulge

Dashedline

overall dimensions

Radius Radius symbolsymbol

RR

Diameter Diameter symbolsymbol””

””

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Marked it Marked it symmetricallysymmetrically  

(2) Dimensions should be marked in the view that most reflects the characteristics of the related shape and location. Dimensions

should not be marked on dashed lines as far as possible.

避免在避免在虚线处虚线处注尺寸注尺寸

SymmetrySymmetry

SymmetrySymmetry

Marked in the same Marked in the same view as possibleview as possible

22ΦΦ

Dimensioning general composite solidsDimensioning general composite solids

16

16

10

4×8

60

4× 30

4040 84×8

1016

60

R8R8

Dimensioning general composite solidsDimensioning general composite solids 15

º

45º

15

45

120

90

17

Φ

Φ

Φ

Larger dimensions placed outside smaller dimensions

(3) All dimensions should be better arranged outside individual view in order to avoid possible overlap of dimension lines and feature lines of the drawing. They should also be arranged following the principle of “Larger dimensions placed outside smaller dimensions”.

(4) For diameters of cylinders and cones, the dimension should be better marked in a non-circle view as far as possible.

Dimensioning general composite solidsDimensioning general composite solids

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(5) There should be no dimension for intersection lines.

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intersection curveintersection curve

intersection curveintersection curve

interpenetration lineinterpenetration line

intersection curveintersection curve

Dimensioning general composite solidsDimensioning general composite solids

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2. Dimension this drawing of components.

3. Point out the dimension which one is incorrect and correct it.

ExercisesExercises

1. Point out the dimension which one is incorrectly..

退出退出前一页前一页

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Avoi dance of dimensi ons i nto a seri es wi th an overal l di mensions

(1)

(2)

R

R

1.1. Point out the dimension which one is incorrectly. .

R

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(1) (2)

2.2. Dimension this drawing of components..

2×Φ Φ

Φ

R

P24P24

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3.. Point out the dimension which one is incorrect and correct it..

×

R

×

×

×

×

×

×

R

×

×

Omit.