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FASTENER HOLE FITS

Clearance, Close-Ream, Transition and Interference Fits

Definitions of common clearance, close-ream, transition and interference fastener-hole fits.

Simplified comparison of clearance, close-ream, transition and interference fastener-hole fits
Concept diagram only: relative hole and shank relationships are shown without dimensions. The approved drawing controls every tolerance.

Key reference points

  • Fit describes the relationship between hole and shank limits.
  • Close fits require controlled drilling and reaming.
  • The applicable drawing defines the required fit and tolerance.

Organised training notes

1Hole-fit family

Keep the four related fit definitions together. The approved drawing or repair procedure selects the fit and its exact dimensional limits.

  1. 1.1 Clearance fitHole limits remain larger than the fastener shank, leaving controlled clearance for installation or removal.
  2. 1.2 Close-ream fitA closely controlled reamed hole provides the minimum specified clearance for a removable fastener.
  3. 1.3 Transition fitThe tolerance bands can produce either a small clearance or a small interference.
  4. 1.4 Interference fitThe fastener shank is larger than the finished hole within specified limits, producing controlled interference.
Training-reference boundary

This summary is not approved repair or maintenance data. Do not inspect, classify, select material, alter structure or perform a repair from this page alone. Use the current applicable SRM, AMM, engineering order, drawing and company procedures.

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