Dowel Pin Tolerance and Fit Standards

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Here is an article written by our engineering team that will guide you on tolerance/fit guidelines for dowel pins. We hope to give you a succinct yet complete depiction of guidelines for different use cases. Please note that these are only recommendations and sound engineering judgement must be applied while taking a decision regarding form and fit for your assemblies.

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1.0 What are dowel pins?

Dowel pins are cylindrical pins usually made of steel, aluminum, or a variety of plastics. They are commonly used in precision engineering to locate parts in large assemblies. Dowel pins usually have diameters or lengths controlled very tightly (e.g. to the range of +- 0.010 mm or above). Combined with deep engineering know-how and knowledge of GD&T, dowel pins are small, but very powerful elements of a precision assembly.

2.0 Different kinds of fit’s

Fits refer to the coupled mating tolerance of 2 components, in this case a dowel pin and a dowel hole. There are a few different kinds of fits, and they vary depending on the overlap between two features. Generally the fits are also dictated by the material that the dowel pins are inserted into. We’ve broken down the tolerances into 3 basic families here:

2.1 Clearance fit

A clearance fit means that the shaft (dowel pin) is smaller than the hole and there is always a “clearance” between the two. Clearance fits are preferred in…