On this day in 79 AD, Vesuvius erupted and forever changed our understanding of the early life of Romans and Greeks. The eruption caused a staggering loss of life, but it also preserved a snapshot in time at sites surrounding the volcano.
We have learned a lot about early woodworking because of the eruption, and my book “Ingenious Mechanicks” explores the early workbenches preserved in paintings at Pompeii and Herculaneum.
But my favorite Roman workbench from this era was preserved by water – not fire. Far north of Pompeii, the Roman fort at Saalburg (now Germany) has what I think is the oldest extant workbench, which was found in a well. I got to examine and measure it. And I reproduced it for the book.
To commemorate this important day, I am giving away the chapter on how to build the Saalburg bench.
Many people have dismissed my love of the low workbenches, but I use mine all the time in the shop and find it practical for many operations (particularly in chairmaking).
Here is the window for our stick-chair livestream. You can also watch it on Vimeo via this link. After it’s complete, we’ll clean up the livestream, add some show notes and post it for those who couldn’t join us live.
Remember: We are Lost Art Press. Not Lost Art Podcast or Lost Art Videoblog. So it’s gonna be a little agricultural.
We have a decent-sized batch of Crucible Type 2 Dividers up in the store today, ready to ship. This is the batch we managed to get done before an end mill decided to go supernova in the mill (no one was hurt, thank you for asking).
I use these dividers every day. Above is a snapshot of me adjusting them one-handed to transfer mortise locations to a chair seat.
The bonus with this batch is it contains Megan Cooties. We had to sharpen these by hand before sending them to the warehouse. Cooties are no extra charge.
I don’t think this is what they meant by wet, green wood. But it works.
Most of my chairs are made with kiln-dried hardwood from the lumberyard. Its moisture content is usually at equilibrium with my shop – just like a good flat woodworker would want.
But I know and respect the wet/dry construction methods used by Jennie Alexander and other chairmakers who use moisture content to strengthen mortise-and-tenon joints. (An oversimplified explanation: A wettish leg mortise shrinks on a dry tenon rung to lock the joint.)
After much flailing about and experimentation, here is how I now imitate that process with wood that is kiln-dried.
Let’s say the joint has a 5/8” (.625”) mortise, which I drilled with a spade bit. I then make the tenon about 15 thou oversized (.640”). This size tenon is too big to enter the mortise.
The oversized tenon, before compression.
Compressing the tenon.
The same tenon after compression with soft-jaw pliers.
So I compress the tenon with soft-jaw pliers. By using a firm grip on the pliers and rotating the tenon, I can compress it to just under 5/8” in diameter (.620”). This tenon will easily fit into the mortise.
Then, when I add hot, wet glue and put the joint together, the tenon swells up to (nearly) its original size, locking the joint.
I know this is true because I’ve done a lot of experiments where I have cut apart sample joints. Plus, I have made a lot of chairs this way. But here is a simple experiment you can try, which is more decimal.
First, some facts. The common woodworking glues (both PVA and hide glue) are about 40 percent water. I use liquid hide glue for almost all of my joinery, plus a little PVA here and there. (Note that there are waterless glues out there, especially polyurethane glue. I haven’t experimented with these glues, so I have no opinion on whether they would work.)
So when I take the compressed (.620”) tenon and dip it in some warm water for a second or two, it swells. (This is much like steaming out dents in pieces of wood with a wet rag and steaming clothes iron.)
After two minutes, the tenon has swollen to almost its original size.
After a couple minutes, the tenon swells to .635”. After an hour or two, it swells to almost its full size (.640”).
When I assemble a chair, I can feel this process at work. The tenons enter the mortises with a little effort. The hot, wet glue hits the mortise and within 10 seconds or so, the joint becomes difficult to rotate. After a few minutes the joint is impossible to move.
If this seems like a lot of work, it’s not. It might add 10 minutes to the entire construction time involved in a chair. But I suspect those 10 minutes of extra work might add years to the lifespan of a chair.
I found an error on page 530 of the book – two missing mortises – that we repeated in the full-size patterns. So we fixed the mistake and issued new pdfs for the book and the full-size patterns. It’s not a huge error. A drawing earlier in the book shows the mortises correctly. And the text is correct. I suspect most of you would do the layout correctly and might not even notice.
It has been one of those weeks where everything feels like it is spiraling down the toilet bowl. Last week while making divider legs, an end mill self-destructed – destroying the fixture that holds our dividers’ legs and damaging the mill’s chuck. Estimate: No dividers for three weeks.
And the chair on my bench is fighting me every step of the way. I trashed two shoes yesterday before settling on something that might work. But I’m looking at this chair as I type this, and I suspect this one might be a burner.
There is some good news: Megan and I finished sharpening up a batch of finished dividers and sent them to the warehouse. So we will have some dividers in the store to sell shortly. And our machinist thinks he might be able to fix the damaged fixture in the mill.
Still, it’s one of those weeks where I fantasize about switching places with a friend who is a third-shift security guard at a factory. The place is so quiet and automated that he spends most of his time writing songs in the control room.