about cipher disk

Because of my carelessness, I lost my cipher disk. As a result, I made a new one. The picture on the left shows my finished product.

During the process I made the cipher disk. I have some suggestions for you if you are interested in making a new one by you own.

Frist, you should use compasses to draw two circles with different diameter.

Second, after you cut the circle, you need to overlay the smaller one on the bigger one snapping to the same center of circle.

Then, you should use rulers with pass through the center of circle and make several lineations with the same angle intervals.

Last, you could find something like clip to connect two disks. Done!

Besides, I found some questions that why Alberti cipher disk does not include the whole 26 letters? Whether we could add another disk to make the cipher reach higher level of security?