Last updated: March 18, 2019
Topic: Technology
Sample donated:

Terminology

* Dimension lines: Lines located between extension lines stoping with an pointer and to include a numerical value. They should be spaced uniformly about. 375 to. 500 inches apart. * Extension lines: Widen off from a position to bespeak a size or location restraint beginning. When extension lines cross object or extension lines. no spread in either line should be made. * Leader Lines: Lines drawn at an angle ( ne’er horizontal or perpendicular ) widening from a note to a characteristic to which the note applies.

Dimension and Extension line arrangement

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1. Always place shorter dimensions nearest to the object lines. Dimension lines should ne’er traverse. However. extension lines may traverse each other. 2. Extension lines should ne’er be shortened.

3. Dimension lines should ne’er co-occur with any object line or centre line of the drawing. Therefore no line should be used as dimension line nor coincide with a dimension line. 4. Dimensions should line up in concatenation manner or be grouped together every bit much as possible. 5. Make non reiterate a dimension. Repeating a dimension will merely confound the reader and could do mistakes in the fabrication procedure. 6. Dimensions should be given in positions where the forms are presented in profile and/or contour.

7. Dimensions should ever be placed off or outside of a position where possible. 8. Hole characteristics must be located and given size in the position where they appear as a circle non as a rectangle or concealed lines. Never dimension to conceal lines. 9. Avoid a complete concatenation of dimensions. Either omit one or utilize mention notation. Reference notation indicates that a dimension is used for information intents merely. Bespeak a mention dimension by puting a parenthesis around the dimension 10. Cylinder location and size restraint. Locate cylinders in the round position but give its diameter and length in the rectangular position.

Dimensioning Symbols

1. Symbols represent particular information which could be hard to double in note signifier. They aid in lucidity. easiness of CAD pulling presentation. and above all. save clip. Seven such symbols are show below.

2. Local Notes: Local notes apply to specific characteristics merely and are connected to a characteristic by a leader. Notes should ever be lettered horizontally. Leader arrows for notes should ever indicate toward the round position of the hole characteristic and if extended. would go through through the centre.

Direction of Dimension Figures
Two systems of puting dimensions are used:

* Unidirectional ( Mechanical ) : Dimensioned numerical values and text are placed so that they can be read merely from the underside of the drawing.

* Aligned ( Architectural ) : Dimensioned numerical values and text are placed so that they can be read either from the underside or right side of the drawing.

Ordinate Dimensioning

Ordinate dimensioning is besides known as Datum dimensioning or Baseline dimensioning. Dimensions may be applied either utilizing dimension lines or arrowheads or without such. A much clearer method of showing a portion dwelling of legion holes is Tabular Ordinate dimensioning. This method involves labeling each hole characteristic with a missive and so supplying a Hole Chart bespeaking the X location restraint and Y location restraint with a complete size description of each hole characteristic. This eliminates the demand for both dimension and extension lines to turn up hole characteristics.

SECTIONING

On many occasions. the inside of an object is complicated or the component parts of a machine are drawn assembled. The interior characteristics are represented by concealed lines in usual orthographic positions. which consequences in confusion and trouble in understanding the drawing. In order to demo such characteristics clearly. one or more positions are drawn as if a part had been cut off to uncover the inside. This process is called sectioning and the position demoing the cut off image is called subdivision position.

A subdivision is an fanciful cut taken through an object to uncover the form or interior building. The fanciful film editing plane is projected on a standard position so that the sectional position with orthographic representation is obtained. A sectional position must demo which parts of the object are solid stuff and which are infinites. This is done by subdivision liner ( cross-hatching ) the solid parts with uniformly spaced thin lines by and large at 45? .

Section Positions

The technique called subdivision positions is used to better the visual image of new designs. clear up multiview drawings and ease the dimensioning of drawings. For mechanical drawings subdivision positions are used to uncover interior characteristics of an object that are non easy represented utilizing concealed lines. Sectional drawings are multiview proficient drawings that contain particular positions of a portion or parts. a position that reveal interior characteristics. In the figure a regular multiview drawing and a sectional multiview drawing of the same portion in the front position. the concealed characteristics can be seen after segmenting. Traditional subdivisions positions are based on the usage of an fanciful film editing plane that cuts through the object to uncover interior characteristics.

What are the types of subdivisions?

A cutting plane does non needfully necessitate to cut the whole object. There are three major types of subdivisions used in technology drawing: * full subdivision – The position obtained when the cutting plane is right across the object. * half subdivision – The position obtained when the cutting plane goes half manner across the object to the Centre line. It is used for symmetrical objects ( the same either side of the centre line ) . The cutting plane merely removes one one-fourth of the object. * portion subdivision – A method of demoing internal item for one little subdivision of a pulling merely.

Each sectional position is linked to a cutting plane identified by a caption placed below the position eg SECTION A-A. SECTION B-B.

Full sectional positions

When the cutting plane is right across the object it consequences in a full sectional position ( normally referred to as a full subdivision ) .

Half sectional positions

Half sectional positions are used when an object is symmetrical ( the same either side of the centre line ) . One half is used as a sectional position to demo the interior and the other half shows the outside position. The cutting plane merely removes a one-fourth of the object.

Part sectional positions

Local or portion sectional positions show typical inside item anyplace on the drawing. Part subdivisions are a method of demoing internal item for one little subdivision merely.

Note
When segmenting a drawing. shafts. pins. bolts and nuts are non sectioned. unless they have any particular internal characteristics.

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