RECOMMENDED HOLE SIZES

Our guide shows the recomended hole sizes within a permitted tolerance range which should be applied when working with Coiled Pins, Slotted Spring Pins, Grooved Pins and Dowels.  Our product portfolio also showcases our full ranges of pins, keys, inserts, spacers and dowel, plus our manufacturing division is decidated to producing custom-made precision components for your unique requirements. Send your enquiries to us for a FREE, competitive quotation.

 

 

Recommended Hole Tolerances For Solid Dowel Pins & Extractable Dowel Pins

 

Hole Material Hardened Steel Mild Steel Aluminium / Zinc / Brass
Interference Fit Pin Diameter Less 5 Microns Pin Diameter Less 25 Microns Pin Diameter Less 35 Microns
Transition Fit Pin Diameter Less 2 Microns Pin Diameter Less 5 Microns Pin Diameter Less 5 Microns
Clearnace Fit Pin Diameter Plus 25-60 Microns Pin Diameter Plus 25-60 Microns Pin Diameter Plus 25-60 Microns

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  

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 abovr, 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.

ARE YOU PART OF THE
TECHNIFAST COMMUNITY?

Join the Technifast eNewsletter service, a monthly update to keep you informed of our latest products, technical guides and industry news. 

Subscribe today and start getting Technifast eNewsletters direct to your inbox.

TWITTER FEED