# Bolt Hole Circle – Lesson 7 – Alphacam Router Tutorial

We will now draw circles with a diameter of 9 and 15 mm, lying on a circle with a diameter of 150 mm. There is a function in Alphacam that makes it easier.

From the **Geometry** tab, expand the **Special Geometries** option and select **Bolt Hole Circle**.

Enter **150** as the **Pitch Circle Diameter**, enter **9** as the **Diameter of Holes**, enter **12** as the **Number of Holes**, and enter **0** for the **Angle for First Hole**.

Click **OK**.

Now we have to specify the center of this circle. It will be in the middle of an existing circle. Therefore, use the **Arc CENTER of** snap and point to the circle.

Repeat the same for circles with a diameter of **15** mm. So once again select the **Bolt Hole Circle** option. Alphacam should remember the previous parameters. Change only the diameter of the hole to **15** and click **OK**.

Again, use the circle **Arc CENTER of** snap to specify the center of the circle on which the holes are.

And in this simple way, we received small circles lying at even intervals on a larger diameter circle.

While drawing circles, let’s draw circles with a diameter of **11** and **17 **mm.

Select drawing a circle using the **Center + Diameter** option.

As the circle diameter, enter **17** and click **OK**. The centers of these circles are offset 20 mm from the corners of the rectangle, i.e. they lie in the centers of roundings with a radius of 20 mm.

To determine the center of the circle, use the **Arc CENTER of** snap. After selecting the snap, simply indicate the fillet and the center will be found automatically. Repeat for the other circles.

Now repeat for circles with a diameter of 11 mm.

Well, our first drawing is ready.