Application of countersinks
Countersinks are often used after drilling to further process the drill hole. But what exactly is "countersinking" and which countersink is suitable for which application? Our guide gives you an overview of the different countersinking methods and types of countersink.
What is "countersinking"?
Countersinking is a drilling process in which existing drill holes are reworked or further processed. For example, profiles or conical surfaces are subsequently created in the drill holes. A distinction is made between three different countersinking processes:
- Countersinking: Creating flat bearing surfaces for screw heads
- Countersinking: Creating countersinks for the head of a cylindrical screw
- Profile countersinking: Creating tapered countersinks for the head of countersunk screws, for example
What is "deburring"?
Drilling often produces material residues/chips at the edge of the drill hole. This can result in sharp-edged drill holes when machining metal (Fig. 1). The removal of these sharp-edged material residues using a countersink is called deburring. Countersinks with an angle of 60° are generally used for deburring. Removing the splinters etc. reduces the risk of injury and prepares the drill hole for the next steps (Fig. 2).
Overview of countersinks
Countersinks differ in their shape and purpose. Countersinks also have a smaller clearance angle and a larger clearance surface than drills, which prevents chatter marks when countersinking. As a rule, countersinking tools are made of HSS steel. Countersinks are provided with special coatings to optimise the processing of different materials. For example, titanium-coated countersinks are also used for countersinking and deburring.
You will find the following countersinks in our range:
Countersink
Countersinks are used for countersinking profiles to create tapered countersinks (Fig. 2 & 3). This ensures that countersunk screws, for example, are flush with the surface of the workpiece (Fig. 4). Holes are also deburred with countersinks.
The angles of countersinks are standardised for the corresponding applications:
| Standardised angle | Application |
| 60° | ➤ Deburring |
| 75° | Rivet heads |
| 90° | Countersunk screws |
| 120° | ➤ Sheet metal rivets |
Using countersinks correctly
- First decide what you want to use the countersink for (countersinking countersunk screws, deburring, etc.)
- Use a calliper gauge to determine the diameter of the screw head.
- Then select the countersink based on the desired application and the size of the screw head. The diameter of the countersink should always be larger than the diameter of the screw head.
- After drilling, use the countersink to create a countersink so that the screw head is flush with the surface of the workpiece.
- If desired, you can further process the drill hole and create a thread, for example.
Flat countersink
Flat countersinks are used to produce cylindrical countersinks (face countersinks) for cylinder head screws, hexagon head screws or nuts (Fig. 2 & 3). This ensures that the screws are flush with the surface of the workpiece (Fig. 4). The guide pin of the flat countersink provides a stable guide while the cutting edges remove the material from the workpiece.
Comparison of countersink types
Correct speed for countersinking
A lower speed should always be used for countersinking than for drilling.
Flat countersinks in particular should be used at the lowest possible cutting speed. For this reason, a speed of 200 revolutions per minute is often recommended when using countersinks. It is safest to countersink at the lowest possible speed.
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