How many vises do you really need to hold your stones while you work? The answer, of course, is none. You can simply hold the stone in one hand and your chisel in the other. But, for several reasons, I prefer to use a vise. In fact, I use three—called “seal beds” (yinchuang 印床) in Chinese—depending on the size and shape of the stone.
My favorite, and the one I use most often, is a heavy vise made of brass and wood. It’s heavy enough to keep from moving around when I work, with ball bearings in the base that allow it to swivel easily. The wooden cross pieces, though hardwood, are soft enough so as not to damage most stone. Many variations of this design are available. The only drawback is it can’t be used for stone smaller than the central opening and, of course, the jaws will only open so far for large stone. On the rare occasion I carve a stone too large for this vise, I simply set the large and heavy stone down on the work surface and carve it without the use of a vise.
Two removable cross pieces accommodate larger stone, with a total height seven centimeters above the work surface for taller stone. It does a pretty good job of holding oddly shaped stone, though no vise is perfect in this regard; clamp it down as tight as possible and the stone may still shift when you push on it with your chisel.
I use a simpler wooden design for stones smaller than will fit in the expensive brass version. And I have a third vise with an even smaller opening for use with tiny stone.
Without the variously shaped openings it’s hard to hold a stone in place. If clamped between two straight crosspieces the stone will tip when you push on it from the side with your chisel.
I don’t use a vise with a round opening, though they are available, since I find a round stone can be clamped just as well in a square hole. In fact, a round opening would require having several different sizes depending on the size of the stone. And, just as the old adage says, I never try to fit a square peg into a round hole (it would probably spin).