This **countersink depth calculator** is used in **metalworking** and **woodworking** to determine the **proper depth** for a **countersink hole**.

**Examples of countersink depth calculator usage:**

Furniture assembly: Determining thecorrect depthfor screws in woodentabletopsorchair legs.Aircraft manufacturing: Ensuringprecise countersink depthsforrivetsin aluminum panels.Automotive industry: Calculating countersink depths forbody panelsandinterior components.

**Countersinking** is the process of creating a **cone-shaped recess** around a hole to allow a **screw head** to sit **flush** with or **below** the surface of the **material**.

## Countersink Depth Calculator

Screw Size | Head Diameter (mm) | Shaft Diameter (mm) | 82° Depth (mm) | 90° Depth (mm) | 100° Depth (mm) |
---|---|---|---|---|---|

#4 | 5.5 | 2.8 | 1.37 | 1.35 | 1.31 |

#8 | 7.9 | 4.2 | 1.87 | 1.85 | 1.79 |

1/4″ | 11.1 | 6.4 | 2.37 | 2.35 | 2.27 |

**Conversion equation**: **1 inch = 25.4 mm**

For the **#8 screw** with an **82° countersink**:

D = (7.9mm – 4.2mm) / (2 *tan(41°))D ≈ *1.87mm*

**Countersink Depth Chart**

Screw Size | Head Diameter (mm) | Shaft Diameter (mm) | 82° Depth (mm) | 90° Depth (mm) | 100° Depth (mm) |
---|---|---|---|---|---|

#4 | 5.5 | 2.8 | 1.37 | 1.35 | 1.31 |

#6 | 6.6 | 3.5 | 1.57 | 1.55 | 1.50 |

#8 | 7.9 | 4.2 | 1.87 | 1.85 | 1.79 |

#10 | 9.3 | 4.8 | 2.27 | 2.25 | 2.17 |

1/4″ | 11.1 | 6.4 | 2.37 | 2.35 | 2.27 |

**Countersink Depth Formula**

The **formula** for calculating countersink depth is:

**D = (OD – ID) / (2 * tan(θ/2))**

Where:

**D**=**Countersink depth****OD**=**Outer diameter**of the countersink**ID**=**Inner diameter**(screw shaft diameter)**θ**=**Countersink angle**(typically**82°**,**90°**, or**100°**)

For a screw with a **6mm head diameter**, **3mm shaft diameter**, and **82° countersink angle**:

D = (6mm – 3mm) / (2 *tan(82°/2))D ≈ *1.52mm*

## How to Figure Out Countersink Depth?

To find the **appropriate countersink depth**:

**Measure the screw**: Determine the **head diameter** and **shaft diameter** of the screw.

**Identify the countersink angle**: This is usually specified by the **manufacturer** or determined by the **application**.

**Use a calculator or formula**: Input the **measurements** into a countersink depth calculator or use the **formula** provided earlier.

**Adjust for material**: Consider the **hardness** and **thickness** of the material being countersunk.

**Test and refine**: Create a **test hole** and adjust the depth as needed for the **perfect fit**.

## How Deep Should I Countersink?

The **ideal countersink depth** depends on several factors:

**Screw head profile**:**Flat head screws**require deeper countersinks than**oval head screws**.**Material properties**:**Softer materials**may require slightly shallower countersinks to prevent**over-compression**.**Aesthetic requirements**: For a completely**flush finish**, the countersink should be slightly deeper than the screw head height.**Structural considerations**: In**load-bearing applications**, the countersink shouldn’t compromise the material’s**strength**.

As a general rule, aim for the screw head to sit just **below the surface**, typically **0.1-0.2mm deep**.

# How Do I Choose a Countersink Bit Size?

Selecting the **right countersink bit** involves:

**Screw head diameter**: Choose a bit that creates a countersink slightly **larger** than the screw head.

**Pilot hole size**: Ensure the bit’s **pilot** matches the screw’s **shaft diameter**.

**Countersink angle**: Match the bit angle to the screw head angle (usually **82°**, **90°**, or **100°**).

**Material**: **Harder materials** may require specialized bits with different **cutting angles**.

**Application**: Consider using **combination drill and countersink bits** for efficiency in **high-volume production**.

# How Do You Dimension a Countersink Hole?

**Dimensioning** a countersink hole on technical drawings involves:

Hole diameter: Specify thethrough-holeorpilot hole diameter.

Countersink diameter: Indicate theouter diameterof the countersink.

Countersink angle: Note the angle (e.g.,82°,90°,100°).

Depth: Specify thecountersink depthor the distance from the top of the material to the start of thecylindrical hole.

Tolerance: Includeallowable variationsfor critical dimensions.

Use **standard dimensioning techniques** and symbols according to **engineering drawing conventions**.

**What is 82 Degree Countersink Formula?**

The **82-degree countersink** is commonly used for **flat head screws**. The formula for an **82° countersink** is:

**D = (OD – ID) / (2 * tan(41°))**

This simplifies to:

**D ≈ 0.5 * (OD – ID)**

Where:

**D**=**Countersink depth****OD**=**Outer diameter**of the countersink**ID**=**Inner diameter**(screw shaft diameter)

This **approximation** works because tan(41°) is very close to **0.869**, which is nearly **1/2** or **0.5**.

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