PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 1
LESSON 1
PRECISION GAGES AND MEASURING TOOLS, AND
TYPES OF FITS, TOLERANCES, AND
ALLOWANCES
TASK 1.
Describe the different types of fits, tolerances, and allowances
used in the machinist trades.
CONDITIONS
Within a self-study
environment
and
given
the
subcourse
text,
without
assistance.
STANDARDS
Within one hour
REFERENCES
No supplementary references are needed for this task.
1.
Introduction
Some machinists are required to work to tolerances of 0.0002 inch, others
to 0.002 inch. There is a vast difference between the two. Many components
are manufactured to very close dimensions.
Therefore, a machinist cannot
afford to make a mistake while measuring or machining workpieces. Once the
piece has been machined, there is no turning back or adding on.
It is,
therefore, important for him to become familiar with precision measuring
tools, instruments, and with the types of fits, allowances and tolerances
required for his job.
2.
Type of Fits
a.
General.
Information concerning fits will be applied to plain
cylindrical parts such as sleeves, bearings, pump wearing rings, and other
non-threaded round parts that fit together. Fit is defined as the amount of
tightness or looseness
1
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