Tom Bussey
05-21-2021, 9:35 AM
Actually I am building a Roubo split top bench and probably one of the most important features of the modern Roubo bench is the leg vise. And the most important feature of the leg vise is how the bottom of the vise operates. One option is to move a pin at the bottom of the leg to different holes depending on the thickness of the part being clamped.
When I was looking through a bench book I came a crossed the cris-cross method and it intrigued me. There is a lot actually going on with the cris-cross. Having thought about, it I plan on doing a post on clamping principals from a metal working prospective. From a metal working view point you will understand what is actually designed into the cris-cross. But that is a different story.
The cris-cross actually take all the weight of the leg vise and moves the leg vise in a parallel direction in and out. The whole assembly pivots on 3 pins. I might add that the easiest way to drill the pin hole in the bench ley and in the vise leg is to use a drill press to drill as deep a hole as possible. I bought a longer drill at a big box the same size and finished the drilling the hole with a hand drill. Sometimes people get caught up in drilling the hole and forget to clamp a block on the back to stop the split out when the drill exits the hole in the back. also Drill the hole before removing the material for the criss Cross. That way the drill will not deflect in the void.
I had have some long 5 /16th bolts so I cut them to length using a cut off disc and a Dremel tool. And filled them to length when when they were in the different components. I use a wood screw to clamp the pins in place to they do not move when it use. It is especially important in the middle of the cris cross. Forget the screw and you will find out very quickly why it is needed.
Anyway the vise moves in and out independently of the screw and take all of the weight. The screw does nothing but the final twist to clamp what ever. Bench Crafted screws and other components are machined in such a way with tighter tolerances so that the vise screw can spin when opening or closing. My bench screw is quite old and the machining tolerances are looser so it sags a little bit and the weight of the screw drops a little and put a bind on the thread so it doesn't spin like Bench Crafted's screw does. But it does open and close with a couple of fingers.
Anyway here are some pictures of the bench leg and vise leg to date. And if you would like to know more about building the assembly let me know.
458025 458026 458027 458028 458029
When I was looking through a bench book I came a crossed the cris-cross method and it intrigued me. There is a lot actually going on with the cris-cross. Having thought about, it I plan on doing a post on clamping principals from a metal working prospective. From a metal working view point you will understand what is actually designed into the cris-cross. But that is a different story.
The cris-cross actually take all the weight of the leg vise and moves the leg vise in a parallel direction in and out. The whole assembly pivots on 3 pins. I might add that the easiest way to drill the pin hole in the bench ley and in the vise leg is to use a drill press to drill as deep a hole as possible. I bought a longer drill at a big box the same size and finished the drilling the hole with a hand drill. Sometimes people get caught up in drilling the hole and forget to clamp a block on the back to stop the split out when the drill exits the hole in the back. also Drill the hole before removing the material for the criss Cross. That way the drill will not deflect in the void.
I had have some long 5 /16th bolts so I cut them to length using a cut off disc and a Dremel tool. And filled them to length when when they were in the different components. I use a wood screw to clamp the pins in place to they do not move when it use. It is especially important in the middle of the cris cross. Forget the screw and you will find out very quickly why it is needed.
Anyway the vise moves in and out independently of the screw and take all of the weight. The screw does nothing but the final twist to clamp what ever. Bench Crafted screws and other components are machined in such a way with tighter tolerances so that the vise screw can spin when opening or closing. My bench screw is quite old and the machining tolerances are looser so it sags a little bit and the weight of the screw drops a little and put a bind on the thread so it doesn't spin like Bench Crafted's screw does. But it does open and close with a couple of fingers.
Anyway here are some pictures of the bench leg and vise leg to date. And if you would like to know more about building the assembly let me know.
458025 458026 458027 458028 458029