Countersink

Defines a conical recess used so a flathead fastener can sit flush or below the surface.

⌵

DIA x ANGLE

A countersink is a conical hole coaxial with a cylindrical hole.

Its angle is selected to match the fastener head, commonly 82 degrees for many inch fasteners and 90 degrees for many metric fasteners.

Use it on through holes where the fastener head must be flush or slightly recessed.

Call out the countersink diameter and included angle with the countersink symbol.

Countersink Drawing Use

Countersink is read with the adjacent dimension, note, or feature control frame so inspection uses the intended feature definition.

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0.04

This symbol defines or modifies a size, shape, or manufacturing dimension rather than creating a GD&T tolerance zone by itself.

Read the symbol with the attached dimension, note, or feature control frame before evaluating the feature.

Verify the controlled feature using the drawing's stated limits, datum setup, and any special notes tied to the symbol.

A drawing includes the Countersink symbol with a related feature requirement.

Identify

⌵

Recognize the Countersink symbol and the feature it modifies.

Read

Adjacent value

Use the attached dimension, note, or frame cells as the controlling requirement.

Inspect

Per drawing

Measure the named feature using the specified interpretation rather than assuming a generic size check.

Countersink clarifies how the feature is defined so the drawing and inspection method stay aligned.

Item	Controls	Typical Placement
Countersink	Dimension interpretation	Next to a dimension, note, or frame
GD&T control	Geometric variation	Feature control frame
Datum reference	Measurement setup	Datum feature or frame cell

This page is part of the drawing-symbol reference set rather than a standalone geometric tolerance category.

When the symbol modifies a feature control frame, read it together with the tolerance value and datum references.