Unit I DIMENSIONING AND SHOP NOTES

-

Unit I DIMENSIONING AND SHOPNOTES the croftslf on obiect is to be monufocturedoccordingto the designerts specificotions, its shope. of drowing mon usuolly needs more informotion thon thot furnished by o scole D I M E N S I O NoSn d S H O PN O T E So r e n e e d e dF, i g ' 8 - l obiect. They ore preDIMENSI0NS define the sizes of the geometricol feotures of on s e n t e di n o p p r o p r i o t eu n i t s o f m e o s u r e - - i n c h e s , m i l l i m e t e r s , e t c . S H O PN O T E Sp r o v i d eo d d i t i o n o li n f o r m o t i o no l o n gw i t h s i z e .

F O RD I M E N S I O N S DIRECTION READING or on ALIGNED D i m e n s i o n so r e p l o c e d o n t h e d r o w i n g i n e i t h e r o n U N I D I R E C T I O N A L m o n n e r , F i g . 8 - 2 . U n l d i r e c t i o n odl i m e n s i o n i n gi s p r e f e r r e d . of the drowing' Unidirectionoldimensionsore ploced to be reod from the bottom ore reod A l i g n e d d i m e n s i o n so r e p l o c e d p o r o l l e l t o t h e d i m e n s i o n l i n e . T h e n u m e r o l s from the bottom or right side of the drowing. ond notes ore lettered Regordless of the method used, dimensions shown with leoders porollel to the bottom of the drowing.

UNIDIRECTIONAL

ALIGNED

t-

l*-

t --l

ing drowings.The UNIDIRECTIONAL methodis pre(erred' Fig. g-2. The rwo occepredmerhodsof dimension

t07

ExploringD rofting D I M E N S I O N I NAGD R A W I N G F r o m y o u r s t u d y o f t h e A L P H A B E T O F L I N E S , y o u w i l l r e m e m b e r t h o t s p e c i o ll i n e s ore used for dimensioning,Fig, 8-3. The dimensionline is o fine solid line ,."j to indicote distonce ond locotion. lt should be fine enough to controsf with the obiect lines, ond is broken neor the center for the insertionof rhe dimension.The line is coppedwith orrowheods.

lu+ -

D I M E N S I OLNI N E

I ro * DEPENDTN9__fUP O ND R AWIN G I

SIZE.

EXTENSION LINE

TI I

DOESNOTTOUCH

3T-

B_

Fig.8-3. Ihe lines used for dimensioning.Note how they confrost with the obiecr line.

The line thot extendsout from the drowing is colled on extensionline qnd proiects 1/gin. beyond the lqsf dimension line. lt should not touch fhe drowing. The smoller or detoil dimensions ore neorest the view, while the lorgeror overoll dimensionsore forthest from the view. Arrowheods ore drown freehond ond should be corefully mode, Fig.8-4. The solid orrowheod is generolly .preferred. lt is mode norrower ond slightly'lonjer thon the open orrowheod.For most opplicotions,orrowheods l/8 in. long ore sotisfo"io.y.

;- { mruc+roFARRowHEAD

+--r\\\

I

/

PREFERRED

I AVOID

t_

Fig. 8'4. Arrowl'reodsare drown(reehond.Ihe solid orrowheodis generolly prelerred.

G E N E R A LR U L E SF O RD I M E N S I O N I N G Dimensions, if they ore to be eosily understood,shouldconform to the following generol . rules: l. Ploce dimensionson the views thot showthe true shopeof the obiect, Fig. 8-5. 2. Unless obsolutely necessory, dimensionsshouldnot be plocedwlthin the views. 3. lf possible, dimensions should be grouped together rother thon scotteredoboutthe d r o w i n g ,F i g , 8 - 6 . 4 . D i m e n s i o n s m u s t b e c o m p l e t e s o t h o t n o s c o l i n g o f t h e d r o w i n g i s r e q u i r e d .A l s o , i t

108

g'

Dimensionsond ShoPNotes

AVOID

PREFERRED

Fig. 8-5. Keep ilre dimensionson lhe view ffiof shows lhe lrue shope of the obiecr.

t-

r-rl-l

il

AVOID

PREFERRED

g o( the drowing. F i g . 8 - 6 . K e e p d i m e n s i o n sgroupedfor eosier understondin

should be possiblethot sizes ond shopes moy be determinedwithout o'ssumingony meosuremenis. 5. Drow dimension lines porollel to the direction of meosurement. lf there ore severol porollel dimension lines, the numerols should be stoggered to moke them eosier to reod, Fig. 8-7. 6 . Dimensions should not be duplicoted unless they ore obsolutelynecessoryto the understondingof the drowing. Omit Fig.8-7. When fhere ore severo/ porollel dimension lines flre numerols should be stoggered to moke lhem sier lo reod.

109 E-

ExploringDrafting

;Dta:2HOLES

.

RECOMMENDED

AVOID AVOID

Fig' 8"8. Avoid duplicating dimensionsunless they orenecessoryto the understondingof the drowing.

u n n e c e s s o r yd i m e n s i o n s ,F i g . 8 - 8 . 7 . Plon your work cqrefully so thot dimensionlinesdo not cross extensionlines, Fig. g-9. 8 . W h e n o l l d i m e n s i o n so n o d r o w i n go r e i n i n c h e s ,t h e i n c h s y m b o l ( n ) n e e d n o t b " - u . " d . 9 . Numerols ond froctions must be drown in proper relotion to one onother, fig. g-iO.

PREFERRED

AVO.D

F i g , 8 - 9 . L i n e c r o s s i n gc o n 6 e k e p t f o o m i n i m u mi f f h e s h o r r e s t dimension /ines ore plocedneri to rhe objecf outline.

2tr

2l/4

CORRECT

2h ZVq

2i

AVOID

F i g . 8 - 1 0 . N u m e r o / so n d f r o c t i o n sm u s t b e d r o w n i n prcperre/ofion fo one onolfier.

D I M E N S I O N I NCGI R C L E SH , O L E SA N D A R C S Circles ond round holes ore dimensionedos shownin Fig. 8-l l. The size representsthe diometer. lf the diometers of severol concentriccircles -ust b. dimensionedon o drowing, it moy be more convenientto show them on the fronl view, Fig. g-12.

lt0

Dimensionsond ShopNotes

1*

ora

[

.u,

+@o

;Low.-!

oree

I

F i g . 8 - l l . C i r c l e s o n d f i o l e s o r e d i m e n s i o n e db y g i v i n g t h e d i o m e t e r .

F i g . 8 . 1 2 . R e c o m m e n d e dw o y s t o d i m e n s i o n c o n c e n f r i c c i r c l e s . N o f e f h o f w h e n l h e m e l h o d t o t h e r i g h l i s u s e d only hol( o right side view is needed,

T h e c o r r e c t w o y t o u s e o l e o d e rt o i n d i c o t eo d i q m e t e r i s s h o w ni n F i g . 8 - 1 3 . T h e l e o d e r ALWAYS poinls to the center of the diometer.

Fig.8- 13. A leoder is used to direct ottention to o note or to .indicofe sizes of orcs ond circ/es. Wfienused wifh orcs ond circ/es the leoder shou/d rodiate lrom their cenfers.

PREFERRED 111 1 i

AVOID

ExploringDrofting

-3

, ,'-i*.

-l

tt

/- bft

i

-'4 7-.r"sR. i lr-&o I K___

Fig. 8-l 4. Recommended woys o{ dimensioning orcs.

' A r c s o r e d i m e n s i o n e db y g i v i n g t h e r o d i u s , F i g . 8 - 1 4 . R o u n dh o l e s o n d c y t i n d r i c o lp o r t s ore dirnensionedfrom cenfers, never from the Fig. g-15. "ig"J,

F i g . 8 - 1 5 . W f i e r ef e o s i 6 l e ; r o u n dh o l e s a n d c y l i n d r i c a lp o r f s o r e dirnensionedfrom cenlers

When it is necessqry to dimensiono series of holes oroundo circle, use o note to designote ihe number of holes, their size ond the diometer of the circle, Fig.-e-tO.

.2 5 0D tA . 4 H OL E S EQUALLY SPACED

,2 50D tA, 3 HOLES

3 DIA.

F i g . 8 - 1 6 . L e { t . T h e c o r r e c fw o y t o d i m e n s i o ne q u a l l ys p o c e dh o l e s . R i g h t , H o l e s t h o t a r e n o t e q u o l l y s p o c e do r e d i r " n " i o n e d t h i s w a y .

D I M E N S I O N I NAGN G L E S Angulor dimensions ore expressed in degrees, minutes ond seconds.Angles ore dimensionedos shownin Fig. g-17.

lt2 ,;.@;

/"\

/

--,\

45"

/---f,

-----l

Qs *\

3oo I

RICOMMENDED

AVOID

_-3

r

F i g . 8 - 1 7 . D i m e n s i o n i n go n g l e s .

SF AN OBJECT D I M E N S I O N I NSGM A L L P O R T I O NO When the spoce between extension lines is too smoll to ploce both the numerols ond the or rowheods,di mensionsore i n d i c o t e do s s h o w ni n F i g . 8 - 1 8 .

l*r

ti-

,r25

J-l__fl_

both orrowheodsa n d n u m e r o l s , d i F i g . 8 - 1 8 . w h e n t h e s p o c e b e l w e e n e x f e n s i o n l i n e s i s t o o s m o l l to ploce s h o w n . o s i n d i c o t e d m o Y b e mensfons

T E S TY O U RK N O W L E D G- EU N I T8 Dimensionsond shop notes ore neededif D i m e n s i o n sd e f i n e Shopnotes provide U n i d i r e c t i o n o ld i m e n s i o n so r e r e o d from Aligned dimensions ore reod from T h e d i m e n s i o nl i n e i s o : o . H e o v ys o l i d l i n e , b. Finesolid line. c . F i n e d o t t e dl i n e . d, None of the obove. 7 . T h e d i m e n s i o nl i n e i s c o P P e dw i t h 8 . Dimensionsore plocedon the views thot show oboutthe drowing. rother thon 9 . D i m e n s i o n ss h o u l db e 1 0 . Dimensionsmust be complete so thot: o . N o s c o l i n go f t h e d r o w i n gi s n e c e s s o r y . b. sizes ond shopescon be determinedwithout ossumingony meosurements. c. Both of the obove. d. None of the obove. need not be used. l l . W h e n o l l d i m e n s i o n so r e i n i n c h e sf h e of the 1 2 .when o leoder is used io indicote o diometer it olwoys points to the diometer.

l. 2. 3. 4. 5. 6.

1t3