Deck 28: Datums Ordinate and Tabular Dimensioning

Question 1

Explain ordinate dimensioning and zero coordinates.

Answer 1

Ordinate dimensioning is a type of rectangular datum dimensioning. In ordinate dimensioning, the dimensions are measured from two or three mutually related datum planes. The datum planes are indicated as zero coordinates. Dimensions from the zero coordinates are represented on drawings as extension lines, without the use of dimension lines or arrowheads. Specific features are located by the intersection of datum dimensions. Ordinate dimensioning is used when there would otherwise be a large number of dimensions and features and close tolerances are required. Datums and ordinate dimensioning are the foundation of numerically controlled machine drawings and precision parts.

Question 2

Machines controlled by data that are specially coded with numbers, letters, and special characters are operated by ____.

A) automated control
B) semantic control
C) numerical control
D) batch control

Answer 2

C

Question 3

Describe computer numerical control.

Answer 3

Machines controlled by data that are specially coded with numbers, letters, and special characters are operated by numerical control (NC). This encoded information defines the path of the machine tool in accomplishing specific tasks. These instructions can be fed into the machine from several different sources-an operator, a computer, a computer network, or portable magnetic media. When the job changes, the instructions must be rewritten to accommodate these changes. This is a relatively easy job and this flexibility is the key to the growth of numerical control. Actually, NC is a broad term that includes traditional approaches as well as more modern developments, such as computer numerical control (CNC) and direct numerical control (DNC). CNC processing and distribution applications are numerous, covering every material imaginable: metals, plastics/polymers, ceramics, composites, stone, wood, fabrics, leather, etc.

Question 4

Describe tabular dimensioning.

Question 5

Describe a datum and how it is used.

Question 6

The dimensions of a coordinate and features that are to be fabricated on coordinates are given in a ____.

A) spatial chart
B) reference chart
C) dimension chart
D) coordinate chart

Question 7

In absolute positioning, all process locations are given as distances from a ____.

A) zero point
B) maximal point
C) predefined point
D) central point

Question 8

Describe the type of dimensioning that the accompanying figure illustrates.

Question 9

Discuss the two reference point systems used to position tools in a CNC machine for work on a part.

Question 10

In ____, the dimensions are measured from two or three mutually related datum planes.

A) ordinate dimensioning
B) tabular dimensioning
C) nominal dimensioning
D) normal dimensioning

Question 11

In ____, dimensions from intersecting datum planes are given in a table.

A) ordinate dimensioning
B) tabular dimensioning
C) chain dimensioning
D) incremental dimensioning