Here's another take on putting a used toothbrush to good use. My toothbrush seems to wear out within a month and worse still, only the top half of the brush wears out while the bottom half seems fine. Must be something wrong with the way I brush my teeth. But not to worry, this ible is sure to put a smile back on ones face, by that I do not mean to use the rotary tool bristle brush as a substitute electric toothbrush.

Materials needed:
1. Toothbrush
2. brill bit
3. hacksaw blade or rotary tool circular saw
4. metal file or sandpaper
5. nose plier
6. pencil

Step 1:

It is important to make sure the final brush does not vibrate when used with the rotary tool. For this the brush needs to be symmetric in terms of weight and the mandrel needs to be attached at the exact center of a circle when the brush rotates. For example the picture below shows a possible layout.

The bristles at the four corners that the circle intersects need to be removed completely using the nose plier.

Step 2: Making the Cut

The brush I actually used had a row of bristles passing through the center of the circle I wanted to use. In this case I used the nose plier to remove one of the bristle clusters from the center of the circle. The hole that was left behind I then used as the hole in which to attach the mandrel after drilling it to completely pass through the other side of the brush.

Remember to try to keep the same number of bristles / group of bristles such that it is symmetric around the center of the hole.

Step 3: The Final Steps

The picture shows the mandrel I used. I attached the mandrel to a hand drill and the toothbrush to a vice, then turned the hand drill so that the mandrel firmly threads itself in the hole on the toothbrush.

Cut off the remaining part of the toothbrush and give hand drill a few turns while holding a pencil against the remaining toothbrush. This should now mark out a circle which we need to file off.

The corners can be cut off using the hacksaw blade and a file used to give a rough round shape. Finally attach the brush to the rotary tool and spin at lowest speed setting. Hold the file against the brush to give it it's final circular shape.