When you say tumbler, do you mean the block is loose and tumbles like a rock in a polisher or the method where the block is fixed in a jig and it turns and tilts while a steel shot paddle throws steel beads at high velocity and blasts it clean. My shop used one of those for years after they cooked ii in a big oven for 45 minutes. It came really clean. It was such a high maintenance piece of equipment, they got tired of fixing it when it broke.