Roubo Is Coming… Part 25

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WoodOwl ship’s auger and 1920’s (pre-Stanley takeover) North Bros brace

After a few days of building up the courage to start boring holes in my newly flattened bench top, the holdfast holes are all now bored. Truth be told, it wasn’t that terrifying a proces after the first hole, even if perforating a newly flattened bench top does feel counter-intuitive.

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Scribing the hole diameter helps to line up the drilling jig)

I don’t tend to make many jigs, partly because I don’t find jig-building all that satisfying (I’d rather be building furniture or musical instruments). But when it came to boring the holdfast holes in the bench top I did decide to make a simple jig which would also be useful for cutting the planing stop mortise. This jig is essentially a 2 1/2″ high piece of hardwood glued to a 3/4″ thick plywood base. The face of the jig is at 90 degrees to the base, so that it can be used as a guide block for a timber framing chisel when paring the mortise walls. A 1″ diameter hole was bored through the jig to provide a perfectly plumb guide for boring the holdfast holes – this is critical if the holdfasts are to function properly. The plywood base is deeper and longer than the hardwood, which allows it to be clamped in position. The whole thing took probably 30 minutes to make, and won’t win any beauty prizes, but it has proved to be very useful.

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Boring a holefast hole with the drilling jig – dirt simple and effective

I started boring the holdfast holes with the rear-most row first, working from the front end of the bench to the back, and then in the opposite direction for the second row. The holes were bored with a 18″ long, 1″ diameter ship’s auger by WoodOwl, driven by my 1920s North. Bros brace. The additional length of the ship’s auger makes it easier to see when the bit is plumb, and also facilitates the use of my simple drilling jig, where the standard bits are too short.

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Before clamping the jig in place, I scribed a 1″ diameter circle around the location of each holdfast hole with a pair of dividers – this made it easy to see when the jig was lined up properly on the centre point. The jig was clamped in place and I started boring out the hole. Once the auger bit screw had engaged with the bench top I checked alignment with a 10″ square as a safety check, and made any minor adjustments to keep the hole plumb to the surface.

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The process is very simple, but even with the fast cutting WoodOwl bits, boring 5 3/4″ thick oak felt a little bit like work and 10 holes took a while. The WoodOwl bit cuts very nicely however, and left wonderfully clean holes which look very neat on the benchtop. The length of the plywood base for the jig worked nicely, as I was able to span the jig across the width of the bench, and also on the diagonal where necessary to avoid the bench legs.

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Testing the Crucible holdfasts

Once the holdfast holes were bored, I did a test fit to check that the holdfasts fitted and gripped properly. The Crucible holdfasts grip like the absolute dickens with only a sharp tap from a lump hammer, so the workholding on this bench will be spot on.

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The completed holdfast layout

With the holdfast holes bored, I was able to check the location of the planing stop mortise, and decided to scoot it back 2″ closer to the front end of the bench, so that there is room to fit a long batten across the width of the bench with one end secured by the planing stop and the other by a holdfast – this will help when planing long panels. The next job is to bore out and chop the planing stop mortise, and fit the planing stop.

4 thoughts on “Roubo Is Coming… Part 25

  1. Inquiring minds would like to ask how and where did you get the holdfast(s) from crucible (I understand you are in the UK). I have a set of French originals, but they are mismatched in diameter (25 and 28 mm) and span, and I am thinking of biting the bullet for crucible’s, since I’m planning a new workbench).

  2. Pingback: Roubo Is Coming… Part 26 | Over the Wireless

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