The Differences Between Counterbore and Countersink Holes

The majority of PCBs require some type of mounting hardware, and many PCB Fabrication designs incorporate non-plated mounting holes for this reason. In order to fit the product elegantly into an enclosure, some clients specify special PCB Drilling Requirements, such as Countersink and Counterbore. At Bittele Electronics, we have both the tools and the expertise to help with these types of requirements, and this article is intended to make sure that you know exactly how to specify for the drilling service you require when you send us your PCB Design Files.

Countersink and Counterbore holes both refer to drilling methods that allow fasteners to sit flush with the surface of the PCB Laminate Material. Broadly speaking, this is done by drilling out a larger diameter for the top few mils of the hole, in order to snugly house the head of the screw.

The main difference between these two methods is that Countersink holes are tapered, while counterbore holes show a more instantaneous transition from one diameter to another. This allows for countersink holes to accommodate flat head socket cap screws, while counterbore holes are designed to accommodate standard socket cap screws.

Most clients will include the specifications for any required countersink or counterbore holes on a Fabrication Drawing, while some choose to include this information on a mechanical layer of their Gerber Files. Either one of these methods will be sufficient for our purposes, but we do recommend including a note on both of these file types to ensure that this specification is never missed.

The figures below show sample specifications for both counterbore holes and countersink holes, as normally shown in the Fabrication Drawing.

If you still find yourself with any questions about Bittele’s drilling capabilities, or to send in the PCB Design Files for your PCB project today, please feel free to Contact Us any time! You can reach us over email at, or call us toll-free at 1-888-812-1949.

Bittele is a full-service provider of low-cost Canada-Based PCB Assembly solutions. In business since 2003, we have established ourselves as a leader in the PCB production industry, and we offer a variety of tailored solutions to meet your specific needs.


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