Tolerancias del dibujo

Update 56 Update 56 A. Wilson by: Bruce SYMBOLS 1.0 GENERAL1

Dimensioning and Tolerancing Symbols

DRAFTING MANUAL

Section 6.1 Page 1 February 1997*

2.1 Diameter - A diameter symbol is placed in front of any dimension value that is a diameter. See Figure 2.

This section is based on ASME Y14.5M-1994. Symbols unique to ANSI Y14.5M-1982 are also described for those who arecontractually obligated to comply with the older standard. 1.1 Symbols permit consistency in the way dimensions and tolerances are specified, and each symbol has a clearly defined meaning. Symbols take less time to apply on a drawing than would be required to state the same requirements with words. The symbols also require considerably less space. See Figure 1.

Figure 2. Diameter Symbol 2.2 CounterboreSymbol - A counterbore symbol combined with a diameter symbol is placed in front of a specified counterbore or spotface diameter. See Figure 3.

Figure 1. Equivalent Symbol and Note 1.2 The symbols are presented in two groups for easier use of this section as a reference. General dimensioning symbols are shown first. Some of these symbols are also used in tolerance specifications. The second set ofsymbols are used for tolerances. 1.3 Symbol sizes are shown in the figures as values proportional to the letter ‘h’. The letter ‘h’ represents the predominant character height on a drawing. If a symbol dimension is shown as 1.5h, and the predominant character height on the drawing is to be 3mm, then the symbol dimension is 4.5mm (1.5 x 3mm). 1.4 Symbol proportions defined in the standard arerecommendations. Some companies find it desirable to vary from the recommended proportions for improved microfilm reproduction capability. Symbol proportions within a company, and certainly within a single drawing, should be consistent. 1.5 Symbols are not generally used in text or notes lists. Abbreviations and symbol names are used in text or notes lists. 2.0 GENERAL SYMBOLS General symbols are usedwith dimensions to clarify the requirement defined by a dimension value and to minimize the number of words or abbreviations placed on a drawing.
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Figure 3. Counterbore Symbol 2.3 Countersink - The countersink symbol combined with a diameter symbol is placed in front of a specified countersink diameter. See Figure 4.

Figures in this section were created using Auto CAD software, a productof Autodesk, Inc. and plotted on a Summagraphics (Houston Instrument Engineered) DMP 160 series plotter.

Figure 4. Countersink Symbol
* Supersedes issue of September 1995

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Section 6.1 Page 2 August 1993*

Dimensioning and Tolerancing Symbols

DRAFTING MANUAL

Update 47

2.4 Depth - A downward-pointing arrow is used for the depth

symbol, and it is placed infront of the depth value in such applications as for counterbore and hole depths. See Figure 5.

2.7 Reference Figure 5. Depth Symbol 2.5 Dimension Origin - A circle used in place of one of the

arrowheads on a dimension line indicates the origin for measurement. See Figure 6. This symbol is not used as a replacement for datums and datum references.

Parentheses enclosing a dimension valueindicates the dimension is a reference value. See Figure 8.

2.6 Square - A square is placed in front of dimensions for square features. See Figure 7. The square symbol is used in a manner similar to the diameter symbol. One dimension is adequate for a square shape when this symbol is used eliminating the need for a second dimension.

2.8 Arc Length - An arc drawn above a dimension valueindicates the shown value is the distance measure along the defined arc. See Figure 9. It may be a distance measured along a curved surface or it may be a distance between two features such as holes in a curved part.

Figure 9. Arc Length

* Supersedes issue of September 1984

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Update 56

Dimensioning and Tolerancing Symbols
example: 3X .250-20UNC-3A

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