Tuesday, December 21, 2010

Dimensioning and Surface Finish

Dimensioning

Linear Dimensioning

 

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






Tolerances and Limits

Different methods of specifying tolerances


  • Direct indication on Drawing
  • Reference to general tolerance notes on drawing
  • Reference to a standard containing tolerances
  • Reference to another document

Examples of tolerance notes


 
 
Dimensioning of fits



 
 
Dimensioning of acceptable deviation of dimensions
 
 
 
 
 
 
 
 
 

Geometrical Tolerancing

Introduction


The notes below relate to use of geometric tolerances on drawing.  The notes are outline in nature to provide general guidance.  This subject is complex and it is wise to consult the standards and have a clear understanding of what is required when including geometric tolerances on technical drawings.  There are clear differences between ANSI Y14.5 and the above noted ISO standard.   The notes below do not address this difference or refer to the ANSI standard in any way.

Geometric Tolerances


Geometric tolerances specify the maximum variation that is allowed in form or position from true geometry.   The geometric tolerance is, in essence, the width or diameter of tolerance zone within which a surface or axis of hole or cylinder can lie which results in resulting feature being acceptable for proper function and interchangeability.

If a tolerance of form is not specified on a drawing for a feature, then the feature as made will be acceptable regardless of form variation.   The tolerances of form control straightness, flatness, parallelism, angular displacement etc. etc.
    The tolerance zone will be one of the following:
  • The area within a circle
  • The area between two circles
  • The area between two equidistant lines or between two parallel straight lines
  • The space within a cylinder
  • The space between two coaxial cylinders
  • The space between two equidistant surfaces or two parallel planes
  • The space within a bent pipe
Tolerance Frame with Symbol identifications


Geometric Toleance Symbols

Indication of datum



Supplimentary Symbols



Tolerance Frame Variations


The tolerance frame can be divided into two or more compartments.
These compartments include from left to right
  • The symbol for the feature to be toleranced
  • The tolerance value..If the tolerance zone is circular or cylinderical it is preceded with a   
  • Letters for datums when the toleranced feature is specified in relation to one, or more datums.
When multiple datums are referenced in the tolerance box they are indicated as below:


Maximum Material Indication in Tolerance Frame


The maximum material condition, when used, is indicated by a symbol placed after the tolerance value, after the datum letter, or both.

See the figures below: 

Geometric Tolerances Maximum Metal Conditions

Additional Frames- Notes


If a single frame cannot convey sufficient information it is acceptable to stack additional frames and/or provide additional notes..
Geometrical Tolarances Extra Information

Positioning of Frames /Datum triangles


The datum triangle is placed on a feature or on an extension of the outline ( but clearly separated from the dimension line) when the datum feature is the line or surface itself

The datum triangle is place on the extension of a dimension arrow when the datum feature is the axis or medium line.
When two datums are indicated they relate to the common axis of the two features
The datum triangle can replace a dimension arrow if there is not enough room.


The datum can be located on the axes or median line when 
  • The axis or median line is clearly for a single feature
  • The axis or median line is clearly formed by two features

Autocad Shortcuts Key



ALT+F8        VBA Run
ALT+F11      VBA Editor

CTRL+1        Properties Palette
CTRL+2        DesignCenter Palette
CTRL+3        Tool Palette
CTRL+4        Sheet Set Manager Palette
CTRL+5        Info Palette
CTRL+6        DBConnect Manager
CTRL+7        Markup Set Manager Palette
CTRL+A        Selects objects in drawing
CTRL+B        Toggles Snap
CTRL+C        Copies objects to Clipboard
CTRL+SHFT+C    Copies objects to Clipboard with Base Point
CTRL+D        Toggles coordinate display
CTRL+E        Cycles through isometric planes
CTRL+F        Toggles running object snaps
CTRL+G        Toggles Grid
CTRL+H        Toggles PICKSTYLE on/off
CTRL+J        Executes last command
CTRL+K        Hyperlink
CTRL+L        Toggles Ortho mode
CTRL+M        (No action)
CTRL+N        Creates a new drawing
CTRL+O        Opens existing drawing
CTRL+P        Prints current drawing
CTRL+Q        Exit
CTRL+R        Cycles layout viewports
CTRL+S        Saves current drawing
CTRL+SHFT+S    Saveas
CTRL+T        Toggles Tablet mode
CTRL+V        Pastes data from Clipboard
CTRL+SHFT+V    Pastes data from Clipboard as Block
CTRL+X        Cuts objects to Clipboard
CTRL+Y        Repeats last action
CTRL+Z        Reverses last action
CTRL+[        Cancels current command
CTRL+\        Cancels current command

F1    Displays Help
F2    Toggles text window on/off
F3    Toggles OSNAP
F4    Toggles TABMODE
F5    Toggles ISOPLANE
F6    Toggles COORDS
F7    Toggles GRIDMODE
F8    Toggles ORTHO MODE
F9    Toggles SNAP MODE
F10    Toggles POLAR
F11    Toggles OTRACK

3A      3DARRAY
3DO   3DORBIT
3DW   3DWALK
3F       3DFACE
3M      3DMOVE
3P       3DPOLY
3R       3DROTATE
A         ARC
AC      BACTION
ADC    ADCENTER
AA      AREA
AL      ALIGN
3AL    3DALIGN
AP      APPLOAD
AR      ARRAY
-AR    -ARRAY
ATI     ATTIPEDIT
ATT    ATTDEF
-ATT -ATTDEF
ATE     ATTEDIT
-ATE   -ATTEDIT
ATTE   -ATTEDIT
B          BLOCK
-B       -BLOCK
BC       BCLOSE
BE       BEDIT
BH      HATCH
BO      BOUNDARY
-BO    -BOUNDARY
BR       BREAK
BS        BSAVE
BVS      BVSTATE
C          CIRCLE
CAM    CAMERA
CH       PROPERTIES
-CH     CHANGE
CHA    CHAMFER
CHK     CHECKSTANDARDS
CLI       COMMANDLINE
COL     COLOR
CO       COPY
CP        COPY
CT        CTABLESTYLE
CYL      CYLINDER
D          DIMSTYLE
DAL      DIMALIGNED
DAN      DIMANGULAR
DAR      DIMARC
JOG       DIMJOGGED
DBA      DIMBASELINE
DBC      DBCONNECT
DC        ADCENTER
DCE      DIMCENTER
DCO     DIMCONTINUE
DDA      DIMDISASSOCIATE
DDI        DIMDIAMETER
DED       DIMEDIT
DI           DIST
DIV         DIVIDE
DJL          DIMJOGLINE
DJO         DIMJOGGED
DL           DATALINK
DLI          DIMLINEAR
DLU        DATALINKUPDATE
DO          DONUT
DOR        DIMORDINATE
DOV        DIMOVERRIDE
DR           DRAWORDER
DRA        DIMRADIUS
DRE         DIMREASSOCIATE
DRM        DRAWINGRECOVERY
DS           DSETTINGS
DST         DIMSTYLE
DT           TEXT
DV           DVIEW
DX           DATAEXTRACTION
E              ERASE
ED            DDEDIT
EL             ELLIPSE
ER             EXTERNALREFERENCES
EX             EXTEND
EXIT          QUIT
EXP           EXPORT
EXT           EXTRUDE
F                FILLET
FI               FILTER
G              GROUP
-G            -GROUP
GD             GRADIENT
GR             DDGRIPS
H               HATCH
-H             -HATCH
HE             HATCHEDIT
HI              HIDE
I                 INSERT
-I                -INSERT
IAD            IMAGEADJUST
IAT             IMAGEATTACH
ICL             IMAGECLIP
IM               IMAGE
-IM             -IMAGE
IMP             IMPORT
IN               INTERSECT
INF             INTERFERE
IO               INSERTOBJ
J                  JOIN
L                LINE
LA             LAYER
-LA           -LAYER
LAS           LAYERSTATE
LE             QLEADER
LEN           LENGTHEN
LI               LIST
LO             -LAYOUT
LS              LIST
LT              LINETYPE
-LT           -LINETYPE
LTS            LTSCALE
LW             LWEIGHT
M               MOVE
MA            MATCHPROP
MAT          MATERIALS
ME             MEASURE
MI              MIRROR
ML             MLINE
MLA          MLEADERALIGN
MLC          MLEADERCOLLECT
MLD          MLEADER
MLE           MLEADEREDIT
MLS           MLEADERSTYLE
MO            PROPERTIES
MS             MSPACE
MSM          MARKUP
MT             MTEXT
MV             MVIEW
O               OFFSET
OP             OPTIONS
ORBIT        3DORBIT
OS              OSNAP
-OS            -OSNAP
P                 PAN
-P               -PAN
PA               PASTESPEC
PE                PEDIT
PL                PLINE
PO               POINT
POL             POLYGON
PR                PROPERTIES
PROPS         PROPERTIES
PRE              PREVIEW
PRINT          PLOT
PS                 PSPACE
PSOLID        POLYSOLID
PTW             PUBLISHTOWEB
PU                PURGE
-PU              -PURGE
PYR              PYRAMID
QC               QUICKCALC
QCUI            QUICKCUI
R                   REDRAW
RA                REDRAWALL
RC                RENDERCROP
RE                 REGEN
REA              REGENALL
REC              RECTANG
REG              REGION
REN              RENAME
-REN            -RENAME
REV               REVOLVE
RO                ROTATE
RP                 RENDERPRESETS
RPR               RPREF
RR                 RENDER
RW                RENDERWIN
S                    STRETCH
SC                 SCALE
SCR               SCRIPT
SE                  DSETTINGS
SEC                SECTION
SET                SETVAR
SHA               SHADEMODE
SL                  SLICE
SN                 SNAP
SO                 SOLID
SP                  SPELL
SPL                SPLINE
SPLANE        SECTIONPLANE
SPE                SPLINEDIT
SSM               SHEETSET
ST                  STYLE
STA               STANDARDS
SU                 SUBTRACT
T                   MTEXT
-T                -MTEXT
TA               TABLET
TB                TABLE
TH               THICKNESS
TI                 TILEMODE
TO               TOOLBAR
TOL             TOLERANCE
TOR            TORUS
TP               TOOLPALETTES
TR               TRIM
TS               TABLESTYLE
UC              UCSMAN
UN              UNITS
-UN            -UNITS
UNI             UNION
V                 VIEW
-V               -VIEW
VP                DDVPOINT
-VP              VPOINT
VS                VSCURRENT
VSM             VISUALSTYLES
-VSM           -VISUALSTYLES
W                  WBLOCK
-W                -WBLOCK
WE                WEDGE
X                   EXPLODE
XA                XATTACH
XB                 XBIND
-XB               -XBIND
XC                XCLIP
XL                XLINE
XR                XREF
-XR            -XREF
Z                  ZOOM




Sunday, December 19, 2010

Job Responsibilities ( Draughtsman / Draughtperson /Drafter )





1.       Learn
·         Learn the technique of study drawings.
·         Learn the technique of discussion

2.       Discuss
·         Discuss with other drafter/senior drafting /drafting coordinator/engineer

3.       Drawings
·         Prepare fabrication and standard drawing assigned by engineer/ senior drafting/ drafting coordinator.

4.       Bill of Materials
·         Learn to prepare B.O.M

5.       Checking drawing  +  Bill of Materials
·         Learn to check your own drawings.

6.       Revise
·         Revise drawings besed on the comment.

7.       Save drawings
·         Save drawing progressively.
·         Save the latest at the end.

8.       Revise
·         Do a revision once the job is completed