Here’s another use for a worn out saw blade. It works best with a blade that is an ATB (alternate top bevel) grind, like most rip blades.

A video going through the build and a quick demonstration:

The blade I’m using is fairly old and has been sharpened a number of times, so the carbide is getting a bit thin. Some of the teeth are chipped and one is cracked from hitting a drywall screw buried in a piece of wood I was cutting. Resharpening it is not practical, since the broken tooth would have to be replaced.
Still, it will be a great candidate for something like this.
I made cut lines on the blade
then drilled the screw holes. It’s easier to hold while drilling the holes now, before the parts are cut out:

I screwed one of the teeth onto a piece of maple out close to the edge, then lined up the other one. The teeth have to slightly overlap:

Screwed the second tooth on, shaped the handle and it’s ready to use.
I’ll use this in the kitchen to quickly put a good edge on a knife. Although I had it held in my vise to do the sharpening in the video, it is designed to be used hand-held.
This type of sharpener won’t put a razors edge on a knife, but it will be close and certainly keen enough for most tasks. Further work with a very fine stone and strop will take it the rest of the way, if you need it that sharp.