Countersinking

Countersinking cuts a conical recess into a hole so that a flat-head screw sits flush with the surface.

Countersinking creates a conical recess around a drilled hole so that a countersunk screw sits flush with the part surface. In WSi it is a Transform workstep applied to sheet cutting or sheet bending nodes.

When to use this process

Use Countersinking when:

• Fasteners must sit flush with the part surface (no protruding heads)
• The design specifies a countersunk screw type
• You need to prepare holes after cutting or bending operations

Countersinking is typically applied after Sheet Cutting or after Die Bending. It is supported on Sheet cutting, Sheet bending, and Tube cutting workstep types.

Step-by-step

1. Select the Sheet Cutting node or Die Bending node in the Tree View or Graph View.
2. Right-click the node and choose Append node(s) (or Prepend node(s)) from the context menu.
3. In the process selector dialog, choose Countersinking. WSi shows the proposed countersink positions derived from the hole geometry.
4. Review the angle and depth; adjust if needed.
5. Click OK. A Transform node (Countersinking) appears in the Graph View.

Result

After running Countersinking:

• A Transform node (Countersinking) appears in the Graph View
• The Tree View shows the countersink positions, angles, and any warnings
• Export data includes the countersink geometry for CNC machining equipment

Editing countersink parameters

To change countersink parameters after the Countersinking node is created, right-click the Countersinking node in the Graph View and select Edit Number of Countersinks to add or remove countersink positions, or adjust the count for individual holes.

You can also edit the countersink angle and depth per hole directly in the node's parameter table.

TIP

Countersinking in WSi is automatically proposed for holes that align with a countersunk fastener standard in the database. You can accept the proposal or manually add additional countersink positions.

Parameters

The parameters for this process are configured in the database — see the Countersinking page.

Technical Background

A countersink is a conical cut made at the top of a drilled or punched hole. Its purpose is to create a recessed seat so that a countersunk (flat-head) screw sits flush with or below the surface of the part — leaving no protruding head. Standard countersink angles are 82° (most common for metric sizes) and 90° (used for imperial/inch fasteners).

The countersink tool has multiple cutting edges (flutes) that shear the material as it rotates. An 82° countersink on an M× bolt will create a seat diameter of approximately M × 1.5 — for example, an M6 bolt produces a seat diameter of roughly 9 mm. Countersinking can be performed as a single operation on a CNC mill or drill press, or as part of a combined drilling and countersinking tool.

For thin sheet metal, a rolled countersink can be used instead of a cutting tool. This method displaces the material rather than removing it, deforming the sheet into a conical shape. The countersink must be deep enough for the screw head to sit flush without protruding; if it is too deep, the part may be weakened.