Description / Abstract:
Purpose:
This information report provides guidance when the ISO
International metric tolerance system for limits and fits per
ISO/R286 or ANSI B4.2-1978 is applied on a standard, and also
provides a selected series of limits and fits for powerplant
construction suitable for holes and shafts up to 500 mm. For holes
or shafts over 500 mm or for limits and fits not shown, ISO/R286
should be consulted.
Application:
The selected series of limits and fits included in this report
are recommended for use whenever a graded series of tolerances are
required. This applies whether the design feature is a fit or not.
Application of only a limited number of the limits and fits in a
design will assist in reducing production costs by confining hole
and shaft sizes to a standard set of limits and therefore reducing
the number of gauges needed. It also allows the production and
quality control area to make greater use of "go" and "not-go"
gauges even for small production runs of parts.
For the sake of simplicity the system refers to holes and
shafts, however this does not limit its use. The system can be
applied equally well when specifying limits and fits for lungs,
slots, parallel surface and tangent planes.