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Friday, August 14th

Countersinks and Counterbores for Printed Circuit Boards


This is a continuation of our PCB-101 series. In this post, we will talk about Countersinks and Counterbores.

This video provides a quick overview. Read on after for more details:

Countersinks and Counterbores

First I will highlight what these are and then what we need to know when manufacturing a printed circuit board that needs to have counterbores and countersinks.

Countersinks and counterbores are not anything unique to printed circuit boards, by the way. They are used in a variety of manufacturing of both metal, wood and other materials.

I also want to thank Dingo from our fabrication department.   Dingo has been working with Bay Area Circuits since it’s inception more than 37 years ago, and has been working in PCB manufacturing since 1966. He took me to school (maybe a little old school even) on countersinks and counterbores.


What is a Countersink?

A countersink is a conical hole that is cut in order to allow for a flat head screw to be used.

Countersink Drill Press

Countersink Drill Press

Why do you need it?

Makes it possible for a flat head screw to sit flush with the surface to make for a very clean look and installation.

 What information do we need to know to manufacture countersinks?

Countersinks most commonly will have either an 82 degree or 90 degree angle so a primary consideration is the desired angle. Additionally, you would need to specify the diameter of the smaller hole, and either the maximum diameter or the depth of the countersink. And, whether that hole is to be plated or non-plated. In most cases, these are non-plated but there could be situations where you may be grounding to a chassis and would need to have plating in the hole.

Counter Sink Angle Examples

Counter Sink Angle Examples


Flat Head Screw

Flat Head Screw



What is a Counterbore?

A counterbore is a cylindrical flat-bottom hole that is cut that also allows for a socket cap screw (has a flat head) to be used. The socket cap screw usually has an allen wrench drive (hex) hole.

Why do you need a Counterbore?

It is typically needed for much more secure and stable mountings.

 What information do we need to know to manufacture counterbores?

Hex Socket Cap Screw

Hex Socket Cap Screw

For a counterbore, we need to know the dimensions of the smaller hole and the dimension of the larger hole as well as the depth of the bore.

Again in most cases, these will be unplated mounting holes but in some cases you may require plating. We just need to know what you want the finished hole size to be.

Ok there you have it, the basics of countersinks and counterbores for printed circuit board manufacturing.

If you have any questions comments or examples of how you have used them please post in the comments below.


This is another post in our ongoing PCB 101 series.

For more information on the basics of PCB manufacturing, check out our related posts:

Step 1
Printed Circuit Board Manufacturing Double Sided ancd Multi Layer Post 1
Step 2
Printed Circuit Board Manufacturing Multi Layer Image Process
Step 3
Printed Circuit Board Manufacturing Lamination and Drill
Step 4
Printed Circuit Board Manufacturing Outer Layer Image and Solermask
Step 5
Printed Circuit Board Finishes
Step 6
Printed Circuit Board Manufacturing Rout and Fabrication
Step 7
Printed Circuit Board Manufacturing Electrical Testing

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