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  • RECOMMENDED HOLE SIZES

    It is important to follow the hole diameter instructions given by the various manufacturers and standards organisations, and the data given below comes from these sources. However, the user should decide in the circumstances of a particular application which hole size, within the permitted tolerance range, to adopt as this can effect the performance of the pin considerably.

    The general principle is that the inserting pin or dowel requires significantly more force at the bottom of the hole tolerance range than at the top. This has the following implications;-

    • The higher insertion force require, the more difficult the assembly operation, and risk of damaging or over-stressing the area of the material surrounding the hole
    • The harder the pin is to insert, the more firmly it will stay in place so in applications where vibration is a consideration, it may be worthwhile to use a minimum hole size.

    Where an interference fit is required (as opposed to a sliding or clearance fit) the dowel must be precision ground and the hole must be reamed.

    The relationship between the diameter of the pin and the diameter of the hole must take into account the ductility of the dowel and the hole material and will vary more accordingly to this factor than according to the size of the dowel itself.

    In hardened steel parts, the hole should be .005 to .008mm (5-8 microns) smaller than the dowel. In unhardened material, the hole should be 0.025mm (25 microns) smaller than the dowel.

    For dowels ground to m6 tolerance (Technifast standard type), the dowel diameters are as follows, and holes should be reamed to 25 microns smaller (of 5-8 microns for hardened steel) using the lower limit of the m6 range as the reference point.

    Recommended Hole Sizes for Spring Pins and Grooved Pins

     

      Coiled Pins (mm) Slotted Spring Pins (mm) Groove Pins (mm)
      MIN MAX MIN MAX MIN MAX
    1.0 1.00 1.04 1.00 1.10 1.000 1.025
    1.2 1.20 1.24     1.200 1.225
    1.5 1.50 1.60 1.50 1.60 1.500 1.525
    2.0 1.99 2.10 2.00 2.10 2.000 2.025
    1.5 2.49 2.60 2.50 2.60 2.500 2.525
    3.0 2.99 3.10 3.00 3.10 3.000 3.025
    3.5 3.48 3.62 3.50 3.62    
    4.0 3.98 4.12 4.00 4.12 4.000 4.075
    4.5     4.50 4.62    
    5.0 4.95 5.12 5.00 5.12 5.000 5.075
    6.0 5.95 6.13 6.00 6.12 6.000 6.075
    7.0     7.00 7.12    
    8.0 7.93 8.17 8.00 8.15 8.000 8.090
    10.0 9.93 10.20 10.00 10.15 10.000 10.090
    11.0     11.00 11.15    
    12.0 11.90 12.22  12.00 12.17 12.000 12.110
    13.0     13.00 13.17    
    14.0     14.00 14.17    
    15.0     15.00 15.17    
    16.0 15.85 16.25 16.00 16.17 16.000 16.110
    18.0     18.00 18.17    
    20.0 19.85 20.25 20.00 20.17    

     

    Recommended Hole Sizes For Dowels

     

    Nominal Diameter   Dowel Diameter m6  
    0.8   0.802-0.808  
    1.0   1.002-1.008  
    1.5   1.502-1.508  
    2.0   2.002-2.008  
    2.5   2.502-2.508  
    3.0   3.002-3.008  
    4.0   4.004-4.012  
    5.0   5.004-5.012  
    6.0   6.004-6.012  
    8.0   8.006-8.015  
    10.0   10.006-10.015  
    12.0   12.007-12.018  
    14.0   14.007-14.018  
    16.0   16.007-16.018  
    20.0   20.008-20.021  

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