I'm always finding new uses for my rotary tool every time I get new attachments. Because of this, it's one of the most versatile tools in my toolbox able to cut, carve, engrave, sand, grind, clean and polish. But certain attachments like a plunge router can run over $20. For DIYers like manuelmasc at Instructables who just needed to make one cut or find themselves in a bind, you can make your own using the bottom half of a plastic jar. A peanut butter container works quite well and you can use the outer ring of the lid to reinforce your cutting edge. You'll also…