Countersink Depth Calculator
Countersink Depth Calculator
Use this countersink depth calculator to determine how deep to drill the countersink to ensure the screw head sits perfectly flush with the surface.
A countersink is a conical hole cut into a workpiece, which allows the head of a screw or bolt to sit flush with or below the surface of the material.
When you're working on a woodworking project and need to use a flat-head screw with a head diameter of 10 mm and an angle of 82 degrees.
Countersink Depth Chart
Screw Head Diameter (mm) | Countersink Angle (degrees) | Countersink Depth (mm) |
---|---|---|
4 | 82 | 0.84 |
6 | 82 | 1.26 |
8 | 82 | 1.68 |
10 | 82 | 2.10 |
4 | 90 | 0.71 |
6 | 90 | 1.06 |
8 | 90 | 1.41 |
10 | 90 | 1.77 |
Countersink Depth Formula
The formula to calculate countersink depth is:
Depth = (Head Diameter / 2) / tan(Angle / 2)
Where:
- Depth is the countersink depth
- Head Diameter is the diameter of the screw head
- Angle is the countersink angle in degrees
Suppose we have a screw with a head diameter of 8 mm and we’re using a countersink bit with an 82-degree angle.
Depth = (8 / 2) / tan(82 / 2)
= 4 / tan(41)
≈ 1.68 mm
We need to drill the countersink to a depth of approximately 1.68 mm for the screw head to sit flush with the surface.
How to Measure the Depth of a Countersink?
- Depth Gauge: This is the most precise method. Place the base of the depth gauge on the surface around the countersink and extend the probe into the countersink until it reaches the bottom.
- Caliper Method: First, measure the total length of the screw. Then, insert the screw into the countersink and measure the exposed length. The difference between these two measurements is the countersink depth.
- Visual Inspection: For less precise work, you can insert the screw and visually check if it sits flush with or slightly below the surface.
Let’s say you have a screw that’s 25 mm long. You insert it into the countersink and measure 23.2 mm of exposed length. The countersink depth would be 25 mm – 23.2 mm = 1.8 mm.
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