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STG Machine has published articles on how to install dowel pins and how to remove them, but it is always important to consider your dowel pin hole tolerances before you begin your project.
Two factors that will greatly impact your hole tolerance are the material, and the type of dowel pin fit. Depending on what type of mate you are trying to achieve, you will want to take both of these factors into consideration before starting your project.
Material and Plating Considerations
In general you will always want dissimilar material between your pin and your base material. The most common type of base material used in manufacturing is aluminum with stainless steel pins. Dissimilar materials will prevent galling and it will make it easier to insert your hardware. If your base material is bare then it should be a fairly straightforward calculation for your tolerance overlap. However, if you are going to have a part plated then you should consult with your plating company for how much build-up you want. Plugging tight tolerance holes prior to plating should also be considered to help ensure tight tolerances are met both before and after plating.
Dowel Pin Tolerance Overlap
The two most common types of dowel pin callouts are press fit and slip fit. A press fit ensures that the pin will remain embedded in the base material unless removed. A slip fit allows objects to be easily removed from the designated hole but ensures a firm fit. We generally recommend the below tolerances when inserting a pin:
Tolerance for press fit in Aluminum: -.0005’’ / -.0007’’
Tolerance for press fit in Stainless: -.0003’’ / -.0005
Tolerance for slip fit in Aluminum: +.0005’’ / + .0012’’
Tolerance for slip fit in Stainless: +.0005’’ / + .0012’’
Please consider all of the above criteria before starting your project and determining dowel pin hole tolerances. If you have any questions or comments please feel free to leave them below. For more information on dowel pins please refer to our ultimate dowel pin guide!
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Resource Center
Swati Bhargava
June 28, 2022 at 5:18 pm
Thanks for this helping information! Do the tolerances mentioned in this article for slip fit and press fit already take into account the standard tolerances of the Dowel PIN?
For example, the Dowel Pin from Mcmaster made of 4037 Alloy steel with diameter 0.1250″ has diameter tolerances: +0.0001″ to +0.0003″.
So per this article, say for getting a SLIP FIT in Aluminum object using the above pin, I can just set the hole diameter to be 0.1250″ with tolerances 0.0005″ to 0.0012″.
Thus we have:
Minimum Diameter of Dowel Pin=0.1251″
Maximum Diameter of Dowel Pin=0.1253″
Minimum Diameter of Hole =0.1255″
Maximum Diameter of Hole =0.1262″
We can find the clearances:
Minimum clearance = Minimum Diameter of Hole – Maximum Diameter of Dowel Pin = 0.1255″ – 0.1253″ = 0.0002″
Maximum clearance = Maximum Diameter of Hole – Minimum Diameter of Dowel Pin = 0.1262″ – 0.1251″ = 0.0011″
Thus, there is always a clearance between the hole and the pin!
STG Machine
June 30, 2022 at 4:11 pm
@swatibh@knights.ucf.edu,
Yes, these tolerances already account for the standard tolerance of a dowel pin.
However, if you would like to be more precise you can subtract our recommended tolerances from your measured values.
In general these guidelines should be fine since most dowel pins are made oversize and usually fall within +.0000/+.0002″