Bench Dogs

Leg Vise, Dog Holes & Planing Stop – Low Cost Roubo 7

Leg Vise, Dog Holes & Planing Stop – Low Cost Roubo 7

With the top and the base assembled, there wasn’t much left till completion of the bench. First up, lets talk about adding a leg vise. I determined the maximum depth of clamping that I desired for my leg vise – too little and the capacity will be too low, too much and the vise will be wonky and move out of alignment. I did some research and chose a 9″ depth (the leg vise screw would be located 9″ lower than the top of the bench). The leg vise is a very simple yet surprisingly effective design. The screw acts against a a pivot point in the parallel guide to produce a great deal of clamping force at the top. The pivot point is determined by adding a dowel through one of holes in the parallel guide, depending on the thickness of the material being clamped.

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The hole for the leg vise screw and the mortise for the parallel guide

With that in mind, I needed an oversize hole for the screw to pass through the front left leg, and a through mortise for the parallel guide. I bored and chopped both of these prior to assembling the base – while you can do it after, it makes it a lot more difficult. The hole is easy, as it doesn’t require fine tolerances. The screw just needs to centre in the hole without touching the leg, or it will bind. The mortise is a bit more fidgety, as it ideally should be no more than 1/16″ larger than the parallel guide in each dimension.

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Gluing up the chop

With the leg mortised and bored, I used it to mark the location on the leg vise chop. I glued up the leg vise chop from 3 oak boards, creating a 30″ long, 8″ wide and 3″ thick chop. With the locations marked, I bored the leg vise screw hole, and a mortise for the parallel guide. My parallel guide was a 15″ long, 3/4″ thick piece of oak. It is important to get the mortise perfect for the parallel guide, as ideally you wouldn’t want to glue it in, in order to keep it replaceable. Before attaching the parallel guide, I shaped the chop a little, using a block plane and handsaws.

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Chop shaped, drilled and drawbored with the parallel guide

I bored the pin holes for the parallel guide, before attaching and drawboring the guide to the leg vise chop.I then placed the guide into the mortise in the leg, with a 1/16 shim at the bottom, and got to work centering the screw in the hole. It takes a bit of fidgeting, but I was able to make¬†sure the screw is not touching the walls at all, and screw in the threaded part. After testing it to make sure the vise was aligned properly, I planed off around 1/16″ from the top of the vise to make sure it was flush to the top of the bench, added some leather to the bench¬†and chop face and I was done!

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Chop aligned and attached!

 

Next up was the planing stop. The planing stop is designed to sit in the gap between the two halves of the top, just below the surface and act as a tool holder when not required. When it is needed it can be lifted up, shifted an inch to the right and it portrudes about 1/2″ from the top, acting as a planing stop. It is simply two boards with a large dado down each, glued together. I made some relief cuts across the width of each board before chiseling the waste out and gluing the two halves together. A little bit of planing later, it was ready to go in. It is important that it has a tight friction fit in the bench, as you don’t want it to move around on you when in use. It will require the occasional touch up with a plane as it moves at a different rate as the rest of the top.

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Planing stop completed – the two dados are what allows the stop to sit below or above the bench surface as required

 

The last thing (other than finishing) left to do was to bore the bench dog holes. For bench dog holes, less is more – you don’t want to lose precious rigidity and mass from the top of your bench for unnecessary holes. I went with offset holes every 4 – 6 inches in two rows, with one extra hole near a corner for wider boards. Of course, if your end vise has a dog, you want one of the rows to be in line with the dog. It helps if you know the reach of the holdfast you will be using (if at all). I use Gramercy holdfasts, and strongly recommend them. For their quality, performance and price, they are hard to beat. You want the holes to be spaced such that the holdfasts can reach halfway across the distance. A standard diameter for the holes is 3/4″. I used a square to help keep my brace and bit square to the top as I went. A bit with sharp spurs makes a world of difference here. With the holes bored, I rounded over the edges with a file to prevent splintering. I made some homemade bench dogs using 3/4″ maple dowel and leather scraps, and they work remarkably well.

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Boring the bench dog holes

And with that, all that is left for the bench to be complete is finishing! That’ll be the last post in this series.

Posted by Prairie Artisan Woodshop in Builds, Split-top Roubo Workbench, 0 comments