Precision Counterboring with a Precision-Made Counterbore

A counterbore is both a tool and the feature that the tool creates. Confused yet? Actually it’s pretty simple. Got a cylindrical flat-bottomed hole that enlarges another coaxial hole? That’s a counterbore. Got a tool used to create that feature? Also a counterbore. When do you need to use the tool or create the hole? Typically when a fastener, such as a socket head cap screw, is required to sit flush with or below the level of a workpiece surface for that crisp, smooth final result. A very shallow counterbore also merits the special name of spotface. In either case, if you need to make that precise enlargement to the top of a hole so that your screws all disappear neatly into your machining surface, come to Aronson-Campbell Custom Grinding for exactly what you need.

Application Matters

Since flush-sitting screws are pretty important in a lot of industries, counterbores can be made to handle a lot of different jobs. A common industry for high volumes of counterboring is the aircraft industry, where aerodynamics require surfaces to be as smooth as possible. Spotfacing is common with forged or cast surfaces in working with metal and plastics. Let us know when you order what you’re going to be machining so that we can make sure we advise you most effectively on your customizations.

Side note: need a hole with conical sides for a flat-head screw? Check out our countersink page.

Counterbore Details

There are two basic sizing preferences for counterboring. Highly specific applications, where you already know the size of the screws you’ll be working with, are suitable for counterbores in standard dimensions that match the screws. For situations where the precise fit is not so crucial, and you just need to make sure the fastener is flush with or below the part surface, you can also order custom counterbores that do not match any specific screw size, but just suit the end goal of your job.

Counterbores are commonly made of high speed steel, and solid carbide – also available as carbide-tipped. You can also choose between solid-piloted and interchangeable-piloted counterbores. The interchangeable-piloted version allows the flexibility of different pilot diameters for a given counterbore diameter. The solid-piloted version is typically stronger and more robust, but not as versatile.

Make sense so far? Then don’t hesitate to start an order for the custom counterbore you need to get your job done and put some dollars in your and your crew’s pockets. If you have questions before that, feel free to contact us and we’ll lend our expert advice.

Solid-Piloted Counterbore

counterbore diagram


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