March 25, 2013

Roubo Style Workbench - Part Four

It has been almost six weeks since I posted the last build update. Progress has continued at steady pace (for me at least) but I just haven't found the time to sit down and upload the pictures so this will be a bit of a lengthy post.

When we last left off I was finishing up the center section of the benchtop. I added one more layer to the center slab to bring it to the target width.

I then started to figure out how I was going to build the throw mortises for the legs into the outer laminations. I ended up screwing together a few scraps and cutting them down to the desired width of the mortises.

I coated the spacers with paste wax to prevent them from being accidentally glued to the benchtop.

Next I marked out where the end of the benchtop will be so that I could locate the leg mortises. On the left side of the bench this wasn't critical but on the right side I need at least 17" of overhang to fit the steel end vise.

I clamped the spacers to the center slab and used them to mark the exact lengths for the next two layers.


I then milled up the stock for the next layers and cut the pieces to size based on the spacers shown above.

More glue and clamps... are you sick of seeing pictures of glue-ups yet?

As soon as the clamps were in place I removed the spacers to make sure they didn't become a permanent part of the workbench.

Rinse and repeat on the other side...

Adding the outer layers was a bit interesting as there were a few humps and bumps along the length of the various pieces that caused a gappy joint when I test fit the outer piece. Despite the open gaps for the mortises the jointer plane was able to span the openings and worked great to flatten out the top face shown below as well as the opposite edge.

As a bit of added insurance to prevent a gappy glueline I used every clamp I had for this assembly. I also added some blue tape to keep the majority of the glue off of the inside of the mortises.

Here is the final benchtop before any flattening.

...and here is it midway through the flattening process. Jack planes are fun.

With the benchtop complete I shifted focus to the legs. The legs will be a 4 layer lamination with the center two layers forming the tenon that would mate with the mortise in the benchtop. I started by milling up these center layers first so that two layers together just barely fit into the mortise.

The legs also have mortises on 2 faces for the lower stretchers. Again, I'm cheating and building the mortises into the layers where possible. On the legs I basically had to cut out a square section from one layer on each leg which is marked out below.

I used the miter gauge on the table saw to cut a series of kerfs in this area. The blade wasn't quite high enough to cut the full depth so I extended each kerf with the handsaw.

I then chopped out the waste with a chisel and mallet.

Below is the cleaned up mortise-to-be.

...and here you can see how this will make a mortise as well as the longer center layers forming the tenons at the top of each leg.

More glue and clamps... you know the drill. After the legs were glued up a used the jack and jointer planes to level out the laminations and square up each face.

I cleaned the dried glue at the tenon shoulders with a chisel to make sure the legs mated tightly with the bottom of the benchtop.

It was satisfying when the first leg finally dropped into the mortise.

A one legged workbench is pretty useless so I followed on with the other 3. I then tweaked each joint to get a tight joint between the shoulders and the bottom of the benchtop.

As mentioned above I was able to build the mortises for the long stretchers into the legs. The mortises for the short stretchers however were done the hard way. I marked out the outline of each mortise with a marking gauge and knife. These shallow cuts will help when it comes time to chisel out the waste on the edges of the mortise. I started by chucking an 1-1/4" auger bit into the 12" brace and went to town boring out the bulk of the waste. Boring is way easier than chopping it out with a chisel in my opinion.

The auger bit pulls its way through the wood with a leadscrew which allowed me to overlap the holes a fair bit.

With most of the waste gone it was time to clean up the edges with the chisels. The long sides were easy to clean up but the ends were tough. This southern yellow pine isn't the hardest wood ever but cutting across the grain was a pain.

I'd never cut a mortise this way before  but it worked out pretty well.

A bench chisel turned out to be the wrong tool for the job when chopping the end grain. In the picture below you can see the the damage that end grain did to the edge.

It took more than an hour but it cleaned up just fine. After spending that much time getting the chisel sharpened up again I decided to try something different on the rest of the mortises. I have a 3/8" mortise chisel which is much beefier and is meant for this brutal work. I didn't use it initially because I figured it was too narrow for the inch-plus mortise but it turned out 3/8" was just about the right size to chop out the corners of the mortise left by the auger bit. Wow, what a difference. With a few solid whacks with the mallet I was able to sink the mortise chisel straight to the bottom without issue. That was probably one of the more enjoyable parts of this project to date.

My next task was to cut the bottom of the legs to the correct length. I lucked out in that my miter gauge was just big enough to register the tenon shoulders into the stop block to set the length. This ensured that each leg ended up the same length.

That's a nice set of legs.


Now that the legs were done I switched focus to the stretchers. The stretchers are made of two layers, one that extends into the mortises and becomes the tenons on each end and the outer layer that fits between the legs and creates the shoulders. In order to ensure that the outer layer fits exactly between the legs I cut some spacers to hold the stretcher at the right height and clamped it to the legs where it needs to fit.

From the backside I then knifed a line where the stretcher meets the leg.

I considered sawing these by hand but since these cuts need to be as close to perfect as possible I chickened out and cut them on the miter saw. I used the laser guide to adjust the saw off from 90 degrees just a bit for each cut to match the angle of the knife line.

More glue and clamps and we have a stretcher.

 The stretchers are roughly 5" tall but the mortises are only 4" so I have to remove about an each at the top to define the top edge of the tenon.

I used the bandsaw to notch out the corner.

With a bit of tweaking to fit each tenon to it's mortise the stretcher fit nicely. Below I added a clamp across the joint just to see how well the shoulders would pull tight when it is finally assembled.

I took a break from the short stretchers to work on the long ones. I started with the front stretcher which also has the added feature of a chamferred rail on the top that will form the bottom guide for the sliding board jack. I followed the same process as the short stretchers except I left the outside face a bit wider and I cut the chamfers with table saw.

Lex offered her assistance during the glue-up process.

Below you can see the front stretcher assembly.

I should have all of the stretchers fitted later this week and will likely end up doing a dry fit of the bench at that point. It will be strange to see the bench right-side-up for once. That should be a good point to take a break and post some more pictures so hopefully the next post isn't quite so biblical in length.

To date I have approximately 50 hours into this project.