**2.1. Tolerancing methods**

The location of a single hole is usually indicated by rectangular coordinate dimensions extending from suitable edges or other features of the pan to the axis of the hole. Other dimensioning methods, such as polar coordinates, may be used.

There are two standard methods of tolerancing the location of holes: coordinate and positional tolerancing.

**1.** Coordinate tolerancing (Figure 2 a) refers to tolerances applied directly to the coordinate dimensions or to applicable tolerances specified in a general tolerance note.

**2.** Positional tolerancing (Figure 2 b –d) refers to a tolerance zone within which the centre line of the hole or shaft is permitted to vary from its true position. Positional tolerancing can be further classified according to the type of modifying associated with the tolerance positional tolerancing, reciprocity requirement (RPR);positional tolerancing, maximum material condition basis (MMC) andpositional tolerancing, least material condition basis (LMC).

**Figure 2.** Overview of the standard methods of tolerancing the location of holes and the geometric tolerance parame‐ ters and symbols.

These positional tolerancing methods are part of the system of geometric tolerancing.

When the MMC or LMC modifying symbol is not shown in the feature control frame, it is understood that RPR applies.

Figure 3 a –d shows the tolerance zones by this way of tolerancing.

**Figure 1.** Form deviation, orientational deviation and locational deviation [1].

tolerant zone around the theoretically correct position is given.

dimensioning methods, such as polar coordinates, may be used.

tolerancing are described in ISO 5458 [3].

in the Knowledge Society

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**2. Tolerancing of features by position**

dimensions or by geometric (positional) tolerancing.

simple gauging procedures.

**2.1. Tolerancing methods**

tolerancing.

The definition of the positional tolerance is given in ISO 1101 [2], and methods for positional

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In the method of positional tolerancing, the location of features is determined by theoretical exact dimensions and positional tolerances (points, axes, median faces and plane surfaces) relative one or more datum(s) to each other. In this case, symmetrical arrangement of the

The location of features is one of the most frequently used applications of dimensions on technical drawings. Tolerancing may be either by coordinate tolerances applied to the

Positional tolerancing is especially useful when applied on a maximum material condition (MMC) basis to groups or patterns of holes or other small features in the mass production of parts. This method meets functional requirements in most cases and permits assessment with

The location of a single hole is usually indicated by rectangular coordinate dimensions extending from suitable edges or other features of the pan to the axis of the hole. Other

There are two standard methods of tolerancing the location of holes: coordinate and positional

**1.** Coordinate tolerancing (Figure 2 a) refers to tolerances applied directly to the coordinate

dimensions or to applicable tolerances specified in a general tolerance note.

Any of these tolerancing methods can be substituted for another, although with differing results. It is necessary, however, to first analyse the widely used method of coordinate tolerancing to explain and understand the advantages and disadvantages of the positional tolerancing methods.

**Figure 3.** Overview of the coordinate and polar tolerances.
