Proto Tech Tip: Countersinking

Every week, Team Protocase is bringing you a Proto Tech Tip video, where we’ll give an informative look at a particular aspect of sheet metal fabrication and CNC Machining.

This week, Allison gives you a rundown on countersinking for flathead screws, and why they are such a useful addition to a custom enclosure or part.

Watch the full video below – or, if you’d prefer to read his Proto Tech Tip, we’ve got the full transcription below the video.

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Hey everyone, Allison here from Protocase with another Proto Tech Tip. Today it’s about countersinking.

So machine screws are either panhead or flathead. In order to install a flathead screw, the cutout that the screw is being installed into must be countersunk.

Countersinking is using a drill press machine to create a conical hole in your part that matches the angle and head size of a particular screw.

Countersinking ensures your screws will sit flush against the surface metal of your enclosure or part. So there are three main reasons why countersinking is typically used. The first is to avoid interference. For example in a full-size rackmount enclosure, if you were to use panhead screws, the enclosure would very likely rub up against the enclosure that is racked above or below. Flathead screws that have been countersunk will create a flush surface, which will give you more clearance.

Another reason why some designers opt to use countersinks is because they need to create a good seal. For instance you may require an enclosure that’s light-tight. Of course, gaskets would also be useful in this scenario.

Finally, countersinking is also great for creating a streamlined look. Lots of designers prefer countersunk screws for the aesthetics.

So there are a few design requirements that you need to keep in mind when choosing countersinking. For one, you should tell us upfront which type of screw you want to use. Every
screw has a corresponding thread size. The thread size also indicates the angle of the countersink on the head. So for example, a thread size of 100 degrees number 2 indicates a countersink angle of 100 degrees with the standard 2-56 thread size.

So another tip: the material of the part being countersunk must also be thick enough to accommodate the head depth of the screw being used. If your material isn’t thick enough your screw is going to bottom out before it can sit flush with the surface. Standard screws are typically 100,90 or 82 degree angles. If you’re wanting to use a fastener that we don’t stock here at Protocase and the outer diameter of the screw head is larger than what we can typically accommodate, just contact us. We can most likely custom dial in on the drill press machine to accommodate what you’re looking for.

Countersinking is typically done before a part is powdercoated. So as you can see on the sample, we have some standard countersinks. On the top, we have countersinks with black sandtex powdercoat and then on the bottom we have countersinks with grain finish.

So typically you should always factor in the nominal thickness that powdercoat will add to your cutout in order to ensure that your fastener will fit into your cutout properly. But with countersinking you actually don’t need to factor in the extra thickness that comes from powdercoat because our countersinks are deep enough to account for that extra
thickness.

So here’s a tip: Protocase Designer is our 3D designer software and that allows you to create countersunk cutouts right in your design. We’ve linked to a tutorial below on that. Feel
free to check out our website for more information.

We put some direct links in the description below about our many fastener options that we offer. Be sure to also check out our blog, which outlines many other technical tips or
just send us an email at info@protocase.com.

Thanks so much for watching this week’s Proto Tech Tip. Happy designing! See you next week