There are many times I would like to just cut out a blank to size, clamp it up and machine the entire top surface. The challenge is that once clamps are added around the periphery, the part then has to be cut out of the block. So that requires another cutting path, more material that is just plain wasted, blah, blah, blah. I typically will cut out a shape with a .25 dia cutter. Then there needs to be some room to avoid the clamps. Next thing ya know that blank that was 6 X 6 is now 6.75 X 6.75. I good saw blade only needs 1/8 extra material. Did I mention that it usually also involves having to do another tool change? Changing tools gets old pretty quickly.
Anyhow, having been in more than one machine shop I thought of the milling vises used in cnc mills. Low profile and easy to use. Finding one is not so easy unless one just won the lottery. But then the things are made of mean, ornery steel. One little mistake and there is your beautiful vise with a ding and a cutter in several pieces. It occurred to me that a cnc router does not need all that precision or humongous clamping power. Tool pressure is a lot less in wood than in most metals.
So here it is, the Mk I, Mod 0:
The part is 1.25 inches off the table surface. The jaws open to 5.5 inches. The "sacrificial" jaws have T-slots machined in to attach them to the main jaws. The crank handle stays in position as the jaw is moved. All of it is wood so if a cutter goes nutz (I always blame the cutter, could not have been me) it wrecks a few pieces which can be easily remade and the cutter may survive.
Some of the screws in this are brass. I am working on finding all brass hardware for it.
My machine has about 7" inches of Z travel so as you can see in the last pic I can put a 3X3 block in the vise and still have plenty of clearance above.
You can also see in some of the pics a little weird block bolted into the t-slot channel. Those are stops. I just put a 1/2 dowel in the collet, lower it down to within about an inch of the surface and then bump the stop up against it and tighten it down. I move on to the next one and repeat.
Design work has already started on Mod 1 and a stop bar holder to locate the end of pieces.