| Mechanical Tolerance Standards Charts
Geometric Boundaries II GD&T Reference Book
Select "Class XX" to access page. Class I - Loose fit - Use for all possible hole - shaft applications where function will permit.
Class II - Free Fit - Running fits with speeds of 600 R.P.M. or over and journal pressures of 500 lbs/sqin or over. Wobble or shake between mating parts very slight. Part will turn and slide freely.
Class III - Medium Fit - Running fits under 600 R.P.M and journal pressures under 600 lbs/sqin and for sliding fits. Wobble or shake between mating parts noticed only on parts with short bearing length.
Class IV - Transitional Fit (Snug) - Closest fit which can be assembled by hand and necessitates work of considerable precision. Should be used where no perceptible shake is permissible and, where moving parts are not intended to move freely under a load.
Class V - Interference Fit - Considerable pressure is required to assemble these fits and the parts are considered more or less permanently assembled. Bushings and similar uses.
Note:
Material basis is steel. The coefficient of expansion of material considered should be checked against the basis temperature of 70 deg F .
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