NKE Hauptkatalog / General Catalogue 2011

Designof Bearing LocationTables of FitsFor general machinery applications the mostfrequent bearing shaft and housing fits aretabulated on following pages inclusive.Fig. 7.3Shaft fi t 75 j5:-21To determine the theoretical tolerance fi elds andwhether the results indicate loose or interferencefi t at the bearing seat each appropriate table liststhe nominal shaft or housing diameters and theirdiameter size tolerance range, dmp for shafts andDmp for housings, to be used in conjunction witha bearing of equal size and to tolerance class (PN)normal tolerance.The following example shows:Shaft nominal diameterISO tolerance field j5Bearing nominal bore diameterBearing bore diameter toleranced mp75 mm+0.006 mm- 0.007mm75 mm(PN)+0.000 mm- 0.015 mm+6 -12-7 7If these meet, the following values occur (pleaserefer to fi g. 7.3):a) A maximum interference will occur when thelargest allowed shaft diameter meets thesmallest permissible bearing bore.In the above example:│+6 + (-15)│ = 21 μm (upper value)b) The smallest interference will occur when thesmallest allowed shaft diameter meets thelargest permissible bearing bore.In the above example:│-7 + 0│ = 7 μm (lower value)c) The probable interference assumes the actualdimensions to lie 1/3 of the toler¬ance valueapart from the tolerance go side.In the above example:12 μm (centre value)Bold negative figures in the each right half ofa field denote interference fit!298www.nke.at