Tolerancing in Engineering Design

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Questions and Answers

What does a straightness tolerance control on a surface?

The curvature of the surface.

The conicity of the cylinder.

The centreline of the surface.

The bending or wavy condition of the surface. (correct)

What would a straightness tolerance on a conical surface ensure?

Uniform rate of taper. (correct)

Equal radius along the length.

Constant curvature.

Circular cross-sections.

What is circularity a condition of?

A circular line or surface. (correct)

An elliptical cross-section.

A cylindrical feature.

A spherical shape.

What is the result of a circularity error?

All of the above. Signup and view all the answers

What is required to control the rate of taper on a conical surface?

A separate tolerance. Signup and view all the answers

What direction does a straightness tolerance on a flat surface control?

In one direction only. Signup and view all the answers

What is required when the same straightness tolerance is required in two coordinate directions on the same surface?

A flatness tolerance. Signup and view all the answers

How can multiple straightness tolerances be shown on a single view?

With short lines terminated by arrowheads. Signup and view all the answers

What is the primary purpose of a circularity tolerance?

To specify the width between two circular rings for a particular cross section Signup and view all the answers

What is the term for the random irregularities from a true circle in a circular feature?

Random irregularities Signup and view all the answers

On what basis is a circularity tolerance expressed?

RFS basis Signup and view all the answers

What is the minimum radial separation between two concentric circles within which all points on the measured surface shall lie?

Circularity error Signup and view all the answers

What is the limitation of measuring circularity?

It does not lend itself to direct measurement Signup and view all the answers

What is the relationship between the circularity tolerance and the size tolerance?

The circularity tolerance must be less than the size tolerance Signup and view all the answers

What is the term for the differences between the major and minor axes of a circular feature?

Ovality Signup and view all the answers

What is the purpose of the concentric circles in assessing circularity?

To find the minimum radial separation between the two circles Signup and view all the answers

What is a geometric tolerance?

The maximum permissible variation of form, profile, orientation, location, and runout Signup and view all the answers

What is the purpose of a feature control frame?

To specify the tolerance of a feature Signup and view all the answers

What is straightness?

A condition in which the element of a surface or a centreline is a straight line Signup and view all the answers

Where is a straightness tolerance applied?

To the view where the elements to be controlled are represented by a straight line Signup and view all the answers

What is the purpose of a tolerance zone?

To specify the maximum permissible variation of a feature Signup and view all the answers

How is a straightness tolerance specified on a drawing?

By a feature control frame directed to the line requiring control Signup and view all the answers

What is the shape of a tolerance zone for a straightness tolerance?

A parallel straight line Signup and view all the answers

For cylindrical parts or curved surfaces, where should the feature control frame be directed?

To the side view Signup and view all the answers

Study Notes

Geometric Tolerancing

Geometric tolerance is the maximum permissible variation of form, profile, orientation, location, and runout indicated or specified on a drawing.
The tolerance value represents the width or diameter of the tolerance zone within which the point, line, or surface of the feature shall lie.

Straightness Tolerance

Straightness is a condition in which the element of a surface or centerline is a straight line.
A straightness tolerance specifies a tolerance zone within which the considered element of the surface or centerline must lie.
Straightness tolerance controls surface elements only and ensures uniformity of rate of taper on conical surfaces.
On flat surfaces, straightness tolerance indicates straightness control in one direction only.

Circularity (Roundness) Tolerance

Circularity refers to a condition where all points on the line or on the circumference of a plane cross-section of the feature are the same distance from a common axis or center point.
Circularity tolerance measures radially and specifies the width between two circular rings for a particular cross-section within which the circular line or the circumference of the feature in that plane shall lie.
Circularity tolerance is expressed on RFS basis and cannot be modified on an MMC basis since it controls surface elements only.
The circularity tolerance must be less than half the size tolerance since it must lie in a space equal to half the size tolerance.

Errors of Circularity

Errors of circularity (out-of-roundness) of a circular line on the periphery of a cross-section of a circular feature may occur as ovality, lobing, or random irregularities from a true circle.

Assessing Circularity

In assessing roundness, the circularity error is the minimum radial separation between two concentric circles within which all points on the measured surface shall lie.
The circularity error can be measured using different approaches, including finding the smallest circumscribed circle and the largest inscribed circle.

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Description

Learn about the application of straightness tolerance in controlling surface elements, including cylindrical and conical surfaces, in engineering design. Understand the measuring principles involved.