Interchangeable systems

Basic size

Upper deviation for shaft

Lower deviation for shaft

Zero line

Shaft tolerance

Basic size

Upper deviation for shaft

Lower deviation for shaft

Zero line

Shaft tolerance

Lower deviation for hole

Allowance Engineering Graphics

Upper deviation for hole

Hole tolerance of size

Fig. 19.9 Elements of interchangeable systems

Lower deviation for hole

Upper deviation for hole

Hole tolerance of size

Fig. 19.9 Elements of interchangeable systems

Nominal size is the size by which a component is referred to as a matter of convenience, i.e. 25 mm, 50

mm, 60 mm thread.

Actual size is the measured size.

Basic size is the size in relation to which all limits of size are fixed, and will be the same for both the male and female parts of the fit.

Limits of size These are the maximum and minimum permissible sizes acceptable for a specific dimension. Tolerance This is the total permissible variation in the size of a dimension, and is the difference between the upper and lower acceptable dimensions. Allowance concerns mating parts, and is the difference between the high limit of size of the shaft and the low limit of size of its mating hole. An allowance may be positive or negative.

Grade This is an indication of the tolerance magnitude: the lower the grade, the finer will be the tolerance.

Deviation This is the difference between the maximum, minimum, or actual size of a shaft or hole and the basic size.

Maximum metal condition (MMC) This is the maximum limit of an external feature; for example, a shaft manufactured to its high limits would contain the maximum amount of metal. It is also the minimum limit on an internal feature; for example, a component which has a hole bored in it to its lower limit of size would have had the minimum of metal removed and remain in its maximum metal condition.

Was this article helpful?

0 0
Pencil Drawing Beginners Guide

Pencil Drawing Beginners Guide

Easy Step-By-Step Lessons How Would You Like To Teach Yourself Some Of The Powerful Basic Techniques Of Pencil Drawing With Our Step-by-Step Tutorial. Learn the ABC of Pencil Drawing From the Experts.

Get My Free Ebook


Post a comment