Geometric Tolerancing

Design for ManufactureGeometric tolerancing

Agreed by ISO 1001 included in BS308 (drawing standard)

Author: Leicester CollegeDate 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)

File Name Unit Outcome Key Words

Design for assembly 1.1, 1.2,1.4 Overview, Cost, quality, reliability, assembly, guidelines

FMS 2.2 Models, work cycles, volume, machine utilisation, automation, flexible, systems

Geometric Tolerancing

3.1,3.2 Geometric, tolerance, system, symbols, orientation, BS, ISO, location, runout, datum

Industrial Robots 2.2,2.3 Robot, industrial, robot arm, Cartesian, polar, cylindrical, jointed arm

Jigs and Fixtures 2.1,2.3 Efficiency, production, jigs, fixtures, tooling, production,

Kinematics 2.1,2.3 Machines, kinematics, Degrees of freedom, configuration, space, work space, robot, joints, forward, inverse

For further information regarding unit outcomes go to Edexcel.org.uk/ HN/ Engineering / Specifications

Geometric Tolerancing

Geometric Tolerancing

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

Geometric Tolerancing

•Only use geometric tolerancing if it is absolutely necessary to the required design function

•It adds to the cost of both manufacture and inspection

Geometric Tolerancing

The symbols used represent a range of potential geometric features of a form of featureFour types

•Form•Orientation•Location•Runout

Geometric Tolerancing

Symbol construction

Description

Toleranced feature indications

direct

By letter

Datum indications Direct

By letter

Datum targets

Theoretically exact dimension

Projected tolerance zone

Max. Metal condition

Geometric Tolerancing

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

Feature symbol Tolerance

Feature symbol

tolerance datum

Geometric Tolerancing

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

Geometric Tolerancing

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.

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