Geometric Tolerancing

Geometric Tolerancing
Design for Manufacture
Geometric tolerancing
Agreed by ISO 1001 included in BS308
(drawing standard)
Author: Leicester College
Date created:
Date revised: 2009
Abstract:
Geometric tolerancing is a method which is widely used in industry when the more basic systems of tolerancing component features does not provide the required accuracy.
The system of geometric tolerancing id detailed together with the particular features of the system.
© Leicester College 2009. This work is licensed under a Creative Commons Attribution 2.0 License.

These files support the Edexcel HN unit – Design for Manufacture (NQF L4)
For further information regarding unit outcomes go to Edexcel.org.uk/ HN/ Engineering / Specifications

Purpose –
Geometric tolerance symbols give precise indication of GEOMETRIC requirement for a given feature / drawing
Symbols universally understood
Used when normal dimensioning and tolerancing are not sufficient for requirements of component / operation

Only use geometric tolerancing if it is absolutely necessary to the required design function
It adds to the cost of both manufacture and inspection

The symbols used represent a range of potential geometric features of a form of feature
Four types
Form
Orientation
Location
Runout

Symbol construction

Tolerance frame
This type of frame used when no datum is required
This type of frame used when a datum is specified – mandatory for some geometric features

DATUMS
A datum may be a plane surface or axis. For practical purposes the plane surface or axis is used for manufacture or inspection
If the toleranced feature is related to a datum, this is shown by a datum letter which is indicated in the tolerance frame by a capital letter

This resource was created Leicester College and released as an open educational resource through the Open Engineering Resources project of the Higher Education Academy Engineering Subject Centre. The Open Engineering Resources project was funded by HEFCE and part of the JISC/HE Academy UKOER programme.
© 2009 Leicester College
This work is licensed under a Creative Commons Attribution 2.0 License.
The JISC logo is licensed under the terms of the Creative Commons Attribution-Non-Commercial-No Derivative Works 2.0 UK: England & Wales Licence. All reproductions must comply with the terms of that licence.
The HEA logo is owned by the Higher Education Academy Limited may be freely distributed and copied for educational purposes only, provided that appropriate acknowledgement is given to the Higher Education Academy as the copyright holder and original publisher.
The Leicester College name and logo is owned by the College and should not be produced without the express permission of the College.

Geometric Tolerancing

by Leicester College- Technology & Engineering Centre

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