# How do you size a countersink hole?

## How do you size a countersink hole?

You will want to choose a countersink that is larger than the bolt size of the hole. Countersink diameter = 1.5 x Bolt Size Hole Diameter. Example: 1/4″-20 Bolt – Multiple the diameter (. 250) x 1.5 = 0.375.

## What is the countersink diameter?

Countersink diameter is the final diameter of the hole after drilling, measured in the start surface. The countersink diameter cannot be larger than the tool diameter.

What is the standard common angle for a countersunk hole?

82° angle
Countersunk-head screws that follow the Unified Thread Standard very often have an 82° angle, and screws that follow the ISO standard very often have a 90° angle. Throughout the aerospace industry, countersunk fasteners typically have an angle of 100°.

What is the countersink depth?

The depth is typically considered as the vertical distance from the opening of the countersink to the “tip”. This tip is the point at which the countersink comes together.

### What is countersunk hole?

A countersink produces a conical hole matching the angle of the screw so that when the screw is fully engaged the head will sit flush or slightly below the surface. A counterbore is used to enlarge the opening of a hole producing a flat bottom so a socket-head screw will fit flush with the surface of the part.

### How is a countersink measured?

QUICKLY MEASURE COUNTERSINK DIAMETERS Simply press the spring loaded, exact angle Gaging Plunger into the countersink and read the dial directly in . 002″ or 05mm diameter increments on the dial face or optional digital indicator. The COUNTERSINK GAGE is a direct reading gage.

How is a countersink calculated?

> A simple rule of thumb is to choose a countersink which is 50% larger than the diameter of the hole > Countersink diameter = 1.5 x bolt size (hole) diameter > Ex: For a 1/4-20 bolt, multiply the diameter (. 250) x 1.5 = . 375. This equates to a 3/8” countersink.

How do you specify countersink on a drawing?

Write the dimensions of the countersink, giving first the diameter of the drill hole, then the angle of the countersink, followed by the diameter symbol and the diameter of the larger hole. This dimension can be given either with a diameter symbol first, or with the word DRILL after the first diameter.

#### How do you calculate the depth of a spot drill?

A spot drill has a 90-degree point angle, which makes it easy to calculate the depth of a hole to be spot-drilled. You simply divide the diameter of the spot-drilled hole. If you have drilled a 0.25″ diameter hole and want a 0.031″ chamfer on the hole, the diameter to be spot drilled will be 0.312″.

#### What is a countersunk hole?

How do you dimension a countersink hole in Solidworks?

(Annotation toolbar), or click Insert > Annotations > Hole Callout . Click the edge of a hole, then click in the graphics area to place the hole callout. and the dimension of the depth.

How is drill point length calculated?

So if you would need 1″ full diameter hole depth with a . 5 drill, you would drill 1.150″ deep. For a 135 degree drill tip, the formula would be 22.5tan(radius).

## How do you dimension countersink in Inventor?

1. Right-click the hole feature and select Show Dimensions.
2. Double-click the hole dimension.
3. In the Hole Dimensions dialog box, modify the values. Note: If the hole does not contain the associated feature, values are unavailable. Hole Diameter. Sets the value for the diameter of the hole.
4. Click OK.

## How do you measure countersink depth?

How deep should holes be spotted?

A long drill can deflect when it initially contacts a flat surface, making spot drilling necessary. Some drill makers agree that for holes more than 5 diameters deep, spotting is needed. Others say that threshold is 7 or 8 diameters deep or more.

What size is a #8 countersink?

A #8 screw takes a 11/64 inch pilot hole in hardwood and a 7/64 inch hole in soft wood. The hole in this countersink is 11/64.

### Why is spotting important before a hole is drilled?

A Spotting Drill’s purpose is to create a small divot to correctly locate the center of a drill when initiating a plunge. However, some machinists choose to use these tools for a different reason – using it to chamfer the top of drilled holes.