A brief Brazing Introduction, and quips about the prospects of sustainable DIY
My house here in Los Angeles is shared between 4 people – between us we work diverse set of jobs, but we all inevitably spend a lot of time on our laptops. Some of us have desks, but we’ve wanted to have a space to telecommute from since we all moved in together this past summer. We have a somewhat usable dining room table but have wanted something that:
- makes it easy to set up as a workspace, and also clear off afterwards for meals/game night/etc.
- has task lighting and power for laptops, that can also get out of the way if we need it to be.
- relatively waterproof and rigid
- fits people on 3 sides within our dining nook.
This worn-out workbench showed up on Craigslist, and while it was definitely not something you’d see right away as a dining room table, the price was alright and the dimensions were exactly what we were looking for. I was into the industrial-worn look, and decided to go for it.
The table arrived very grimy and soaked in machine oil – I imagined it had been the backdrop to quite a few metalworking projects. My immediate reaction was to take some mild degreaser and try to remove as much of this as possible. It was fowl but did come off pretty easily. the surface revealed was even more stratched and cracked than I thought. It had some old finish in places, and elsewhere the surface was bare wood soaked in (I presume) years of oil.
After removing the massive plywood stiffener in the back, I noted that the table would be pretty wobbly without some something to replace this. Returning the plywood wasn’t an option: it’s heavy, not very nice looking, and gets in the way of table-sitters on one side. I brainstormed a few options:
- Cable tension members from the legs to the tabletop: cheap, but cables are prone to slipping, and it might be hard to install/make everything cleanly. It also only provides strength in tension – this might be fine, but relying on all connections for stiffening is less than ideal.
- Threaded rod members and ball joint ends: This would be stronger than cable, they can support somewhat while in compression . However it requires bulkier connections than cable. It requires less tension and is not likely to slip at all. Overall, this feels right given the industrial aesthetic I’m going for.
- Solid braces between the legs and top: These would be made out of wood (ehhh) or sheet metal (I don’t have the tools to cut). Then screws into the legs and top. f
Of these, 1 and 2 allow for the largest bracing possible, and 2 can take more strain than 1. Thus, I decided to go with a threaded-rod installation. The actual layout of the tie rods was dependent on the available locations for mounting, and maximizing leg and knee room under the table.
This decision meant that a custom part was in order – unless I sent the tie rod ends through the tabletop1, I would need mounting brackets of some sort on the underside of the tabletop. Time to acquire a new skill! I’ve been thinking about the process of brazing aluminum recently – it’s quite low-tech, compared to welding, and both the cost and setup are more palatable to my current budget/workspace. I decided these brackets would be a perfect application to give it a go, picked up a blowtorch, and set to work fabricating the parts.
The parts to assemble were a block of bar stock and a round spacer – I sourced both out of 6061 AL to make the brazing process as straightforward. For the actual braze material, I picked up this kit from McMaster, which comes with a separate flux (other brazing rod I found for aluminum comes with the flux baked in – sounds easy, but just like stick welding, the results are messy) . To prep the surfaces, I flattened the spacer slightly with a file to increase contact with the plate – I’m not sure if this was necessary, but it helped with keeping things stable in the end. To tie things off, I used some annealed steel wire to hold the parts together.
There’s so much to learn, but here are a few takeaways from the first go:
- A big upset – Metals expand when heated! be ready for things to shift around, or use clamps where expanding helps you out (by pressing into the material more, for example)
- Clear your space, you may need to come at the part from more than one angle with the torch. I worked on an open concrete pad outside.
- Get ready for some messy surfaces after blasting with a map-pro gas torch (wire or plastic brush attachments for a drill are a great way to clean it up afterwards)
- Getting to temperature is a uphill battle. This attempt was immediately reminiscent of soldering a circuit board with beefy thermal vias – convection is far more effective at transferring heat than is intuitive at human-scale temperatures (and at brazing temperatures, radiation starts to play a role too!). Like in PCB assembly, a pre-heat of the part (using a propane oven or even a toaster oven?) would be a great help in getting the part to temperature.
- even brazing under a shelter of something fireproof might help – you don’t lose as much of the heat, and prevent convection cells from forming over the part
- You cannot touch your work while brazing, so be prepared with implements or clamp it down exactly where you want it to be. my partially melted glove (wearing those was a good move I guess) is a reminder to me for next time.
In the end, they were not the prettiest things – but the joints worked very well! Brazing, contrary to popular (or at least my own) belief, is just as strong as welding, so I have confidence other parts of the table will yield before they do.
The rest of the finishing was a tried & true technique of sanding, oiling raw wood bits, and applying polyurethane. For this project I used Danish oil and hand-rubbed poly finish from Watco, and the latter went on very nicely, even on top of old finish and the dark oil-soaked masonite tabletop (sanding and much degreasing helped with this sticking). The bottom shelf was another story – formerly a basic piece of plywood, it was very weathered and coated in nasty grey enamel paint and yet more machine oil. I decided to go nuclear on this piece, and used several courses of CitriStrip to remove the paint. This process was awful and left the un-stained sections of the board raw – I added a few applications of red oak stain to match the oilstains as best as I could.
We’re happy with how it turned out! combined with a few stools swiped from Craigslist, it’s giving us all of the urban cafe vibes we were hoping for. and the braces make it incredibly rigid – if I need some extra room for the next project in the queue, I know where to go!
1. Yeah yeah, the table is already full of holes…not the same as a stabby bit of metal though.