Traditional parting tools are relatively wide (about 1/4”), but when parting off pieces, this can be quite a lot of wood to waste.

Eddie Castelin describes how to make one using an old reciprocating saw blade.

After shaping the blade, I cut a slit in a piece of pine, covered the base of the blade in polyurethane gorilla glue and set it in place in the handle. It’s not particularly pretty, but it is effective.