Jun 15, 2009

Selection of Preferred Fits for Your Applications – Hole and Shaft Basis

Sliding Linear Shaft Guide H7 g6

Here are some guidelines for selecting proper fits for your application. To find the exact tolerances for each fit with respect to shaft or hole diameter please refer to any data handbook.  

Clearance Fits

  • Loose running fit for wide commercial tolerances or allowances on external members. Hole Basis - H11/c11, Shaft Basis - C11/h11
  • Free running fit not for use where accuracy is essential, but good for large temperature variations, high running speeds, or heavy journal pressures. Hole Basis - H9/d9, Shaft Basis - D9/h9
  • Close Running fit for running on accurate machines and for accurate moderate speeds and journal pressures. Hole Basis - H8/f7, Shaft Basis - F8/h7
  • Sliding fit not intended to run freely, but to move and turn freely and locate accurately. Hole Basis - H7/g6, Shaft Basis - G7/h6
  • Locational clearance fit provides snug fit for locating stationary parts; but can be freely assembled and disassembled. H7/h6, Shaft Basis - H7/h6

Transition Fits

  • Locational transition fit for accurate location, a compromise between clearance and interference. Hole Basis - H7/k6, Shaft Basis - K7/h6
  • Locational transition fit for more accurate location where greater interferance is permissible. Hole Basis - H7/n6, Shaft Basis - N7/h6

Interference Fits

  • Locational interference fit for parts requiring rigidity and alignment with prime accuracy of location but without special bore pressure requirements. Hole Basis - H7/p6, Shaft Basis - P7/h6
  • Medium drive fit for ordinary steel parts or shrink fits on light sections, the tightest fit usable with cast iron. Hole Basis - H7/s6, Shaft Basis - S7/h6
  • Force fit suitable for parts which can be highly stressed or for shrink fits where the heavy pressing forces required are impractical. Hole Basis - H7/u6, Shaft Basis - U7/h6

Reference: Preferred Metric Limits and Fits, ANSI B4.2-1978

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