My grandfather cobbled together a saw blade connected to a grinder motor with an automotive V belt, and surrounded the thing with a wood frame and chicken wire and a plywood top.
Pretty dangerous, but it did work well enough. Not sure where he got the bearing setup for the saw blade, but to my knowledge, the blade hasn't been removed in 30 years. he used to sharpen it in place, so I imagine its something hard to undo or permanent.
He never properly rigged up the power switch, and the blade spins down just like an unbraked bench grinder, so it remains incredibly dangerous for a couple minutes spinning after the fact with no noise. The on/off switch is of course underneath and behind where the motor is.
x2 to all the comments to buy a saw of craigslist or similar. Having a braked stop for blade spin is a pretty nice feature after you watch a blade spin silently for a few minutes.
