Step 2: 2d illustrations
I used Corel Draw to draw my patterns because it plays well with the laser cutters and is easy to use, but Adobe Illustrator will work as well. I won't be going into the details of using these programs or how to use them to print on the laser.
There will be two disks (or rectangles, or whatever shape you want your cup to have) with holes cut around the edge for the paintbrushes to go.
For the top disk, which has its center removed, you will draw two concentric circles, with enough space between them to fit your largest brush with a little bit extra for structure. Then draw a third concentric circle in the middle of these to mark where the center of the holes will be, this circle will be deleted after all the holes are drawn.
Using your measured diameters, draw the holes for each paintbrush. I added a thousandth of an inch to each diameter to ensure that the holes wouldn't be too tight.
I then marked the first hole with a number "1" with a small bit of the tip hanging onto the edge of the circle which will be etched by the laser, leaving a mark at the first hole. The rest of the holes are just placed in order, moving clockwise.
After drawing all of the holes, draw straight lines connecting the centers of those circles to the center of the disk.
For the bottom disk, draw a smaller concentric circle which will mark the center of the holes on the second disk where they intersect with the straight lines, to ensure that the holes in the bottom disk will line up with the holes in the top disk.
After drawing all of the holes in the second disk, select only these holes and move them away from the top disk in the drawing. Then draw the outer circle on the bottom disk, there is no inner circle because the bottom is solid. I marked the first hole on this disk as well with a small number "1."
Now you can delete the construction lines used to mark the centers of the circles.