Roubo Is Coming… Part 16

DSC_1564-2

Transferring the baseline with the Hamilton traditional marking gauge

Today is a momentous day – the joinery for the Roubo bench is now all cut. The one exception to this is the mortise for the planing stop, which will wait until the bench top has been flattened. But right now, all of the structural joinery is done, which feels like a huge milestone.

DSC_1565-2

The Vesper sliding bevel transfers the dovetail shoulders

Cutting the dovetail sockets for the legs is much quicker than cutting the mortises, but in many ways it feels more nerve wracking. Cutting a square mortise to the right dimensions is relatively straight forward, all told. But cutting the angled shoulders for the dovetail sockets – critical joints which will be visible every time I step up to the bench. That feels pressured. As often is the case, in practice it was not as tough as I had expected, although I am glad that I started with the rear pair of sockets first (these will face the workshop wall, so I won’t see them very often), to warm up. Breaking the operation down into a clear set of stages helps, as does remembering that joinery like this is just a series of fundamental hand skills (accurate layout, cutting to the line, and some chisel work to remove the waste).

DSC_1569-2

Cutting the slopes with the Skelton Panel Saw

First I transferred the layout from the underside of the slab (where I had previously traced it from the legs) to the top of the slab. This is simply a case of taking the precise angle of each side of the dovetails, and depth of baseline, from one side of the slab and striking corresponding lines on the other side.

DSC_1573-2

A motise chisel pops out the waste

After a bit of experimentation, I found that it was easier to cut the angled shoulders with a coarse cross-cut hand saw rather than a back saw, and my Skelton Panel Saw made short work of this critical cut. Setting the bevel to the right angle and standing it a few inches from the cut provided a clear visual guide as to how far to angle the saw plate. Cutting joinery with a hand saw feels counter intuitive at first, but works very well. I started each cut at the near corner, where I could see both the line across the width of the slab and also the angled line on the face of the slab. I knibbled a saw kerf along these two lines, and once I had hit the baseline of the angled cut, and the far corner of the straigh line, I allowed the toe of the saw to drop, taking full length strokes of the saw until the cut was complete. This is very much how I cut tails for furniture-sized dovetails, just on a much larger scale.

DSC_1578-2

Removing

To remove the waste I also cut five relief cuts in each socket, and then knocked out most of the material with a 1/4″ mortise chisel and mallet, working from each side of the slab into the middle. To avoid bruising the interior of the socket walls, I removed the waste from the middle of the socket first and then cleaned up the waste at the edges. The waste pops out easily, making this a very efficient way of hogging out a lot of material.

DSC_1582-2

A completed socket

To take the sockets to final depth, I use a similar approach to how I cut the mortises. First I deepen the baseline with a 2″ chisel and sharp tap from a mallet, followed by a 1 1/2″ wide chisel and mallet to get very close to the baseline. Once there is only a small amount of material left I moved to the big timber framing chisel. Although this chisel is huge, I find that it is very effective as a paring chisel when working across the grain, as the sheer mass means that it will cut without riding up over any difficult patches of grain, resulting in a flat bottomed socket. Ordinarily I would use a router lane for this task, but the sockets were deeper than my router plane could reach.

DSC_1581-2

Using a timber framing chisel to true up the bottom of the socket

My next task, once my slab moving team have helped get the slab back onto my existing bench, will be to test fit the legs into their mortises and to tune the fit where necessary.

DSC_1584-2

The slab now has all of the joinery cut

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s