Pitch Circle Dimension
- Last UpdatedApr 27, 2023
- 2 minute read
A Pitch Circle Dimension (PDIM) is another form of radial dimension. Refer to Pitch Circle Dimensions for further information.
Radial Dimensions have a dimension centre, defined by the DDNM (Design Data Name) attribute. The attribute is an attribute of the RDIM itself, this is normally defined by the origin of the element dimensioned. Refer to Radial Dimensions for exceptions to this. The value can be (for example) the origin of a CYLI or of a (filleted) PAVE (Panel Vertex).
The other principal attribute of an RDIM is the dimension attribute key, AKEY. The attribute is a word attribute that stores the code of a dimensional attribute of the design element type that is to be dimensioned. The default value of AKEY is DIAM.
The table indicates which attributes of which design element types can be dimensioned using an RDIM.
|
Element Type |
Attributes |
||
|---|---|---|---|
|
CYLI |
DIAM |
||
|
NCYL |
DIAM |
||
|
SLCY |
DIAM |
||
|
NSLC |
DIAM |
||
|
DISH |
DIAM |
RADI |
CRAD |
|
NDIS |
DIAM |
RADI |
CRAD |
|
RTOR |
DIAM |
RINS |
ROUT |
|
NRTO |
DIAM |
RINS |
ROUT |
|
CTOR |
DIAM |
RINS |
ROUT |
|
NCTO |
DIAM |
RINS |
ROUT |
|
SNOU |
DIAM |
DTOP |
DBOT |
|
NSNO |
DIAM |
DTOP |
DBOT |
|
CONE |
DIAM |
DTOP |
DBOT |
|
NCON |
DIAM |
DTOP |
DBOT |
|
VERT |
DIAM |
FRAD |
|
|
PAVE |
DIAM |
FRAD |
|
|
SEVE |
DIAM |
FRAD |
|
The command:
Q AKEYLIST
(at a Design element) returns the list of possible AKEY settings.
Most of the AKEY settings are genuine database attributes; however, the DIAM keyword has different meanings at different elements. For some Design elements it is a genuine attribute, for others it is derived:
-
DIAM is a genuine attribute of Dishes (DISH, NDIS) and all Cylinders (CYLI, NCYL, SLCY, NSLC).
-
For a Torus (RTOR, NRTO, CTOR, NCTO), DIAM give the centreline diameter of the element, for example, twice the average of RINS and ROUT.
-
For Snouts (SNOU, NSNO) and Cones (CONE, NCON), DIAM is taken to be DBOT, the bottom diameter.
-
For Structural Vertices (VERT, PAVE, SEVE), DIAM is taken to be twice the fillet radius (FRAD) if it is set. The origin is normally the position of p9 of the vertex.
The centre of a Radial Dimension is normally defined by the origin of the element dimensioned, except for the AKEY settings:
-
For DTOP and DBOT, the dimension centre is the centre of the appropriate end of the primitive, this also applies to DIAM for Snouts and Cones.
-
For FRAD, the centre of the fillet radius is defined by one of the many p-points of the Vertex (p8 or p9), this also applies to DIAM if the FRAD value is being used.
-
The RADI attribute of a dish (DISH, NDIS) is the knuckle radius. The CRAD attribute of a dish is the cap radius. The centres of these radii are derived. Both these AKEY settings are only sensible for a sideways view of a tori-spherical dish.