Countersinks: angle, type & material
Start from the angle, because it has to match the head of your screw and it is the most common mistake. A countersink opens the seat that lets a screw sit flush with the surface, or breaks the edge of a hole. It works in interrupted cutting at low speed; what matters is a clean cut without chatter, not speed.
THE ANGLE5
The angle has to match the head of your screw. The number is the included angle of the cone: 90° means a 90° cone, not 45° per side. DIN 335 standardises three angles: 60°, 90° and 120°. The 75° (rivets) and 30° fall outside them.
Careful: metric flat-head screws are 90°, but American ones (UNC/UNF) are 82°. They are not interchangeable: an American screw in a 90° countersink will not sit flush.
The default, and the angle of metric flat-head screws (DIN 963, DIN 965, DIN 7991, ISO 2009). If you are driving a metric countersunk screw, this is your angle. It also covers general deburring and edge-breaking.
The classic angle for deburring: the sharper cone enters small and cross-drilled holes easily. It is also the angle of lathe centres: the centre hole that takes the point is 60°. Standardised under DIN 335.
A very open angle, for sheet-metal rivets and for a shallow chamfer: it breaks the edge on large holes without cutting a deep cone. It also suits hard materials, where the open angle stresses the workpiece less. Standardised under DIN 335.
The angle for rivet heads. It is not one of the three standardised by DIN 335 and is not a substitute for 90°. You choose it when the rivet or the drawing calls for 75°.
A special angle, outside DIN 335. A very sharp cone, for specific applications where the drawing calls for 30°.
THE TYPE OF TOOL4
Careful: two different tools live here: countersinks cut a cone for a flat-head screw, while the Άλλεν ones cut a flat pocket for a cylindrical head, which is why they have no angle.
Three cutting edges to DIN 335 C, the standard form. The three edges share the load and give a cleaner cone, with less chatter than a single-flute.
A single-flute countersink with an oblique hole (roughly 45° to the axis) through the cone: the chip escapes through the hole instead of jamming between the tool and the workpiece. It leaves a result free of burrs and chatter: the simple, reliable choice for deburring.
This is not a countersink. It is a DIN 373 counterbore: it cuts a flat cylindrical pocket so the cylindrical head of a socket-head (Allen) screw sits below the surface. It is not a cone, which is why it has no angle at all. It has a pilot that centres in the existing hole, in versions for a threaded or an unthreaded hole.
A set of 90° three-flute countersinks in a case, with the most common diameters together. The economical way to cover a range from the start.
THE MATERIAL YOU ARE CUTTING6
Start here. Pick the material you are cutting and the collection filters down to only the tools that work it. The letters P/M/K/N/S/H are the ISO 513 standard, used by every manufacturer; the same letter means the same material in any catalogue.
In detail, per group: [P] Steel · [M] Stainless · [K] Cast iron · [N] Aluminium · [S] Titanium · [H] Hardened.
Plain and alloy steels: the largest and most forgiving group. They give a long, continuous chip, so chip control is what matters.
Stainless steels. They work-harden locally as you cut them, weld to the edge, and do not carry heat away. They want cobalt, a steady feed with no dwelling, and plenty of coolant.
Cast irons. They give a short, crumbling chip, but the material is abrasive and eats the cutting edge. Here you need abrasion resistance, not heat resistance.
Non-ferrous: aluminium, brass, copper. Soft and fast, but they throw a bulky chip that sticks. They want few flutes, large flute valleys and high revs.
Superalloys and titanium (Inconel, Ti). Very low thermal conductivity: the heat does not leave with the chip, it stays in the edge. Low speeds, steady feed, lots of coolant.
Hardened materials, typically above 45 HRC. They demand carbide and a thermally stable coating; plain HSS simply dulls immediately.
THE TOOL MATERIAL3
Click a material to filter the collection. For a detailed description of the grades see the Cutting Tool Materials article.
The classic high speed steel with high hardness and resistance to fracture, ideal for straightforward work.
High speed steel with 5% cobalt for increased resistance to high temperatures. Suitable for stainless (INOX) and hard steels.
Tungsten carbide with cobalt, extremely hard and rigid. For very high cutting speeds in CNC and maximum tool life, but sensitive to vibration and impact.
THE COATINGS2
Click a coating to see only the countersinks that have it.
A coating offering high thermal stability during cutting. It delivers maximum tool life in hard materials and high-speed machining (HSC), and even makes dry cutting possible.
A hard ceramic coating with the characteristic gold colour that provides effective wear protection. It is the standard solution for longer tool life across a wide range of materials.