BS EN ISO 6411:1997 pdf download Technical drawings — Simplified representation of centre holes
1 Scope and field of application
This InternationalStandard specifies the simplifiedrepresentation ofcentre holes and their designationSimplified representation of centre holes may beused particularly when is not necessary to show theexact form and size and where the designation ofstandardized centre holes is sufficient forinformation.
2 References
ISO 128, Technical drawings – General principles
ofpresentatton.
ISO 866. Centre drills for centre holes withoutprotecting chamfers – Type A.
ISO 2540. Centre drills for centre holes withprotecting chamfers – Type B.
ISO 2541, Centre drills for centre holes with radius
form – Type R.
ISO 3098/1, Technical drawings – Lettering -Part 1: Currently used characters.
ISO 6428.Technical drawings – Requirements formicro-copying-.
3 Indication on drawings
3.1 Requirements
Generally, three different requirements may bedefined on technical drawings for the form and sizeof centre holes.
a) centre hole is required on the finished part;b) centre hole can be accepted on the finishedpart,but is not a fundamental requirement;c) centre hole shall not exist on the finished part32 Simplified representationThe symbols representing centre holes and theirapplication to the end face of a shaft are shown incolumn 2 of Table 1.
33 Designation of centre holesThe designation of centre holes is dependent on thedrill and may be indicated with reference either toan International Standard or to any other standarddealing with this subject.
The designation of the centre hole itself consists ofa reference to this International Standard:the letter for the type (R A or B):
the pilot diameter d:
the outside countersink centre holediameter D.
The two values are separated by a solidus.Example: a centre hole2), type B with d = 2,5 mmand D; = 8 mm may be indicated on the drawing as:
IS0 6411-B 2,5/8
4 Interpretation of indication
The relationship between the various designationsused to specify the centre holes, the dimensionsrepresented by the given designations,anddimensions depending on the centre drill used areshown in Table 2.
Further details specifying the dimensions of thecentre hole, to be indicated preferably on thedrawings,are given in Annex A.

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