BS EN ISO 5458:2015 pdf download

BS EN ISO 5458:2015 pdf download.Draft BS EN ISO 5458 Geomentrical Product Specifications (GPS)- Geometrical tolerancing – Positional and pattern tolcrancing.
Rule B: Independency between members 01 repetition or dependency rule for homogeneous pattern
8y default, based on the independency principle defined in ISO 8015, a geometrical specificabon of form, orientation. location or run-out, without modifier, applied to it geometrical features (n being greater than one), is equivalent to n independent geometrical specifications: each geometrical feature shall be considered individually and each specification shall be considered individually (independent between them). The resulting independent tolerance zones correspond to an inipbcit indication of the & (separate zones) rnoditier: the a11 arounC modifier does not create itself a united feature or a pattern.
When positionat tolerancing Is applied to several geometrical features and all the non•redundant degrees of freedoms of the tolerances zones are un-locked, either the SZ (separate zones) modifier or the CZ (combned zone) modifier shall always be indicated In the second comparlment of the tolerance indicator.
NOTE The rule allows the potential conflict ut interpretation between ISO 1101:2012 and the toriner ISO 5458:1996 lobe resolved lsee Annex B).
To create one homogeneous pattern, the modifier CZ shall be Indicated in the tolerance section of the tolerance indicator.
To create a new level of pattern defined as a homogeneous pattern of more than one homogeneous patterns. an additionat C modifier shall be indicated after the sequence defining the previous level of pauern
EXAMPLE One U In the tolerance section detnea a single pattern The sequence C1 C2 C3 m the tolerance section defInes a pattern of patterns of patterns (pattern of level three)
Rule E: Toleranced features and tolerance zone of an homogeneous pattern
When more than one single leature (complete or not) Is the subject of a same geometrical specification, and the modifier CZ is indicated in its second con’iparlment, the toleranced feature oonssts of the collection ol the considered geometrical features and the tolerance zone Is a combwied zone consisting of the set of individual zones constrained between them in orientation and location.
Rule F: Independency or dependency rule between homogeneous patterns
When nx is indicated above the tolerance indicator and k leader lines are attached to it, or when nx is indicated above the tolerance indicator and the a11 around” symbol (covering k single features) is used or when nx is indicated above another indication kx above the tolerance indicator and one CZ modifier and one SZ is indicated in its second compartment, then:
the number of patterns is equal to .
— the tolerance apøes as a set of n independent combined zones, each applying a set of k geometrical features (see Figure 8a).
When the indication nx above the tolerance indicator and k leader lines are attached to it, or when nx is indicated above the tolerance indicator and the a11 around” symbol (covering k single fealures) is used or when nx Is above another indication kx above the tolerance indicator and two consecutive CZ modifiers are indicated in its second compartment, then:
— the toleranced feature is defined as the pattern of the set of the 1* considered geometrical features: and
the tolerance zone is a combined zone, which is defined as the set of nic individual zones constrained between them in orientation and location, and only one pattern exists (see Figure 8b).
NOTE The meaning of a geometrical specification. applied to n identical dependent patterns, composed by k geometrical features, andicatect by CZ CZ modifier in the tolerance section. is ecisvalent to the mearang of the specification appbed to a pattern composed by nxk geometrical features, Indicated by CZ modifier In a lolerance section
If it is necessary to identify a pattern, a surrounding double dotted narrow line shall be used and an identifier letter shall be attached to it (see Figure 9).