Countersink A Countersunk Screw

Having a flush flat surface can create a nice affect within your material/workpiece. In some cases, Screw Heads shouldn’t be flushed for select reasons, but in other cases it is not necessary for them to stick out. To keep the screw heads flush requires a process called Countersinking.

 Countersinking from RUKO Shop UK


What are Countersinks?

Countersink Drill Bit Tools typically come in two different shape styles. A Standard Angled Countersink (also referred to as a Slotted Taper) or Flat Countersink. These two forms have different variations such as Material Types, Head Angles and Head Shapes.

Countersinks from RUKO

Materials can include HSS, HSSE-Co5 and other Hard Metals. With head coatings of TiN, TiAlN or Nano Technology Compound (RUnaTEC) options available. Which material is best suited depends on the applicational use (refer to “Applications of Countersink Tools” section of this blog).

Head Shape options frequently found are defined by the purpose they serve. Standard Countersinks/Angled Countersinks have a conical shaped head. These serve a purpose of deburring or countersinking a pre-existing drill hole. Cross-hole cutters are intended for burr and chatter free countersinking whilst forming two cutting edges. Flat Countersinks provide a fixed guide which is inserted into the pre-drilled hole. Their cylindrical shaped head are ideal for cylinder and hexagon head screws and also nuts.


Standard Angled Countersinks have different head angles to provide different styles of countersinking. For the purpose of Countersinking a Countersunk Screw, a 90° Angled Head should be used (this is UK and European Standards. United States Standards state an 82° Angled Head Should be used). For other angle definitions and their purposes, please refer to the table below.

Countersink Angle





Rivet Heads


Countersunk Screw (US Standard)


Countersunk Screw


Countersinking Sheet Metal Rivets



What can be Countersunk?

Nuts and different Screw types can be countersunk. Nuts require a flat countersink tool whereas Screws can use a flat, angled or slotted taper, dependant on the screw type. Countersunk Head Screws or Lens Countersunk Head Screws require a standard Angled Countersink/Slotted Taper (typically with a 90 Degree Angle to the drill bit piece). Cylinder Head, Round-Head and Hexagon Screws require a flat countersink.


Applications of Countersink Tools

Different Countersinks have different sizes, angles, head shapes and manufactured materials. The RUKO table below outlines the specifications of the Countersink Drill Pieces and what they are compatible with and which surface materials they are best suited to/for.

 Countersinking Table of Applicational Uses

Countersinking Depth Capabilities

When countersinking a screw, you cut with the countersink the depth by feel.


The Countersinking Process

RUKO Shop UK Safety Notice

The process is very simple:

  1. To begin you must measure the diameter of the screw head (or nut). This is critical, as you will need to use a countersink with a larger diameter.
  2. Start your countersinking drilling process into the desired material surface/location of the countersunk screw (use the depth by feel to know how far to drill).
  3. Remove the countersink tool from the surface material. Remove any excess chips or debris to ensure your surface is clean.
  4. Align your screw/nut into the newly created drill hole.
  5. With the screw/nut in place, screw it till flush with the surface.

Countersunk Screw HeadCountersunk Nut

The results show a countersunk screw or nut in place that is flush with the surface. For visual aid, please refer to our Applicational Images and YouTube video below.




RUKO and TERRAX offer high-spec Countersink Products for all Countersinking Processes. Browse through the selection of Countersink Drill Bit Tools at Quality Tools UK. These include newly developed RUnaTEC Coated Countersinks which utilise Nano Technology to enable a high-performance, smoother finish with a 30% time saving process and a 60% Longer Service Life.

RUKO ULTIMATECUT Countersink Products from RUKO Shop UK





Still Need Assistance with Countersink Tools? Check out our other Countersink Blog Here! Or Contact Quality Tools UK Today!

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