Engineering, Manufacturing Tolerance Limits Fits Charts
This Calculator will determine the preferred size and limit tolerances for a force or shrink fit per ANSI B 4.1.
FN 1 Light drive fits are those requiring light assembly pressures, and produce more or less permanent assemblies. They are suitable for thin sections or long fits, or in cast-iron external members.
FN 2 Medium drive fits are suitable for ordinary steel parts, or for shrink fits on light sections. They are about the tightest fits that can be used with high-grade cast-iron external members.
FN 3 Heavy drive fits are suitable for heavier steel parts or for shrink fits in medium sections.
FN 4 and FN 5 Force fits are suitable for parts that can be highly stressed, or for shrink fits where the heavy pressing forces required are impractical.
Other types of fits: See --> Preferred Tolerances & Fits Calculator RC - LT Fits
RC - Running or Sliding Fits
LC - Clearance Locational Fits
LT - Transition Locational Fits
LN - Interference Locational Fits