depends what you are making. I dont see why you couldn't use them, but it is likely to be sized (I assume) for a wood burner, so by the time you cut usable pieces, it is only going to yield small bits. there are better options out there, but it depends a bit on what you want.
when you say general practice, aside from perhaps cutting joints, I would practice by making something. You could join 2 bits to practice a dovetail. Alternatively you could make a bookend, by errrr joining 2 bits with a dovetail. it helps focus attention when there is a defined outcome.
