Introduction: The Hairpin Table
Runner Up in the
Furniture Contest 2017
Another hairpin tutorial?
The classical wood table with hairpin leg. But this time, we start building the wood plate AND then make the legs ourselves. This is not a description for assembling buyer stuff.
This goes out to all furniture fans on instrucTABLEs, waiting in the newsletters for some sexy wood and steel projects.
So here is the story:
Step 1: What Is This Piece of Wood?
So I got lucky when I discovered an 15-30 year old unknown wood plate in our garage in Germany. Until today nobody can tell me what wood species it is. Some think it's teak, some say it's from the southeast of Asia. But for sure it's huge, tropical and hardwood. The diameter is really big for a teak wood. It is also difficult to count the years, the guesses go from 100-180 years.
The plate has a average diameter of 100cm (ca 39'') and a thickness of 15cm (ca 6'') with one flat side. It is to big and heavy to just use the whole as a table.
So the challenge is clear: Sawing
Step 2: Sawing the Slice
Cutting the wood right, was definitely the most difficult step of the whole project. I'm not a expert, so please have some mercy with me;)
The plate was stored in a garage outside with cold temperatures.
The big danger of cutting is, that the plate just tears apart because of tensions. Tensions develop in the growing process of the tree. Also problematical are temperature differences in the wood and the following thermal expansions. Another problem is opening the pores, that held back tensions.
So result of all this is the same: The plate rips apart.
The cut it is definitely like playing roulette, but at least you should maximize your chances ?
The biggest win you get with tempering your plate. Tempering completely the wood takes its time and should be slow enough to not tension the plate more with it. My experts advised me to temper my garage cold plate to living room temperature in six to twelve months. Finally I stored it for 18 months. First in a not heated workshop, afterwards in a heated wood workshop with controlled humidity.
If you don't have a flat side on your wood slice, you have to router it before sawing. The internet is full of tutorials;)
Also in the sawing process you can mess up with your plate, by putting to much radial and tangential force on the plate. To surely not ruin the project here, I decided to visit a local sawmill. There biggest saw gate had a cutting space of 80cm (31'') and some extra centimeters for chip removal. So they gave it a try. It was difficult to saw and some parts got burned from the blade. And after cuts like these, you can throw away your saw blade.
Here comes the result: The plate did not rip apart. Not even a bit. You can see some smaller cracks, but nothing what happened recently.
Now we are almost through the danger zone. One last thing to kill every chance of a crack. To close the pores of the wood as fast as we can.
Step 3: Sanding With Love
We all know that sanding is the never ending and patience-taking step. Here you can show your true love to your wood plate and discover the treasure inside.
The grit number is the amount granulation/meshes per square inch (25,4 mm by 25,4).
I used a random orbit sander, but you can also use other types of sanders. For the sanding I generally started with a 60 grit, for difficult parts I used down to 40. Afterwards followed another round with 80.
To not scratch the wood, don't put too much force on the machine and try to make big moves. I know it costs a lot of patience to sand bigger parts slowly instead of sanding small parts fast, But to get a nice result, you also have to sand exact enough in the first layers. Scratches afterwards are difficult or impossible to sand with higher grit number.
The next sanding grit I used directly 240. Afterwards you see directly your imperfectness and where you still need some extra sanding. So time to do it right.
After finally having a smooth 80 grit I go up to 120. Now you see how the real treasure of the wood is coming out. Sleeping beauty, wake up.
Suddenly the sanding is fun, because I can see the results of the work. I definitely fell in love.
So I directly show my love with another 240 and 400 sanding. Now it feels smooth like a baby's bottom.
Step 4: The Finish
The right finish is the next challenge.
Varnish vs. Oil - We all now this never ending discussion in furniture projects. At the end, make your choice on the use and your personal priorities.
I am surprised, how well the wood turned out during the sanding. To not ruin this beauty, I choose a Danish oil and coated it 3-4 times.
For the second table I want to try another oil (leave advises in the comments).
Step 5: Bending the Legs
Now we start to fabric the table legs.
First we bend the steel rod, prepare a plate and some holes, weld everything together and finish it with a sanding and some paint.
You can use rod of steel between 8-12mm (1/3'' to 1/5'') to bend without heating the steel. To bend 12mm without problems, make sure to build an extra stable rod bender. In case of high tensions you better warm the steel with a Bunsen burner. I would not recommend colt bending with more than 12mm rods.
I hope the bender construction is clear. The bender has two components: the base and the handle. The first bolt on the handle is the connection between the components. The second bolt presses the rod to bend the curve. So especially the bolts should be stable enough. Make use to use full material. The longer the handle, the bigger force you can put on the rod. But be careful, that all components can handle the force (unless the rod). The distance between the bolts can be tight. My advice is 16-18 mm (0,6-0,7'') to bend 12mm rods.
You can screw or force the whole construction to a stable work bench. After the first tries you can also determine the exact bending point and angle measured from fixed points on your base plate.
Step 6: Preparing the Angle Plate
Angle plates are also available to buy...or you make them on your own. You know, what we will choose here.
I've tried different measures but for my hairpin legs I recommend at least 150mm (6'') lengths and a width of minimum 40mm (1,5''). For the final table I've used a width of 60mm (2,4''), which turned out satisfying.
The flat steel should be at least 3mm (0,12'') thick. The thicker, the better.
Welding the flat angle and the bent rod together you burden the angle a lot. The angle can bend, because of heat tensions. Make sure, the angle is thick enough, your welding tool is correctly adjusted and don't put to much heat on the the angle.
You can cut the flat stell with 45° on the ends. Weld it together and grind over. If you are not a practiced welder, you better test your skills before on some scrap parts. If welding is totally new to you, please contact a patient welder or try your best with youtube tutorials.
Depending on you table plate you can add some wholes for screws.
Step 7: Getting the Same Result
Now you can produce one hairpin leg. But how can you get two or three more, that will fit for a even table?
The trick is that all the legs have to pass your "quality control".
In the photos of this step you can see the helping tools. On a flat board, you check the correct total length and opening angle. Make sure to flip the leg to also check unwanted bends.
My preferred leg high is 400mm (16''). With my vertical setting angle I cut the bent rod after ca. 430mm (17'') and I used the total length rod length of 980mm for one leg.
If your product matches your expectations you can cut the overhanging ends.
The next tool helps you to connect your angle plate with the normalized bent rod. Here you prove the vertical setting angle of your table. This helping construction holds the angle plate in a fix position (at least two point contact). Then you lean the bent rod on a levelled vertical post (look on photo). It is important, that the pole is in a exact levelled position and that the angle plates are uniformed products.
In the next step you can weld the positioned components together. If you are not a practiced welder, you better test your skills before on some scrap parts.
Step 8: Post Processing
Almost done, so in the post processing you can grind the weld until a smooth result. If your weld did not turned out decent, you can use different tools. The rough part with a angle grinder, for fine work use for example a finger grinder.
If you place your coffee table inside a house, you can use regular car paint or the metal spray paint of your taste. Better spray two coats for sufficient protection.
And the legs are finish:)
Step 9: Assembling
In the final step you connect wood plate with the hairpin legs.
In my case it was a little tricky to define the mid of the plate.
Because of the differing diameter, I marked optical the mid of the surface (50% of the surface vs 50% of the surface) from different positions. Also the distance to the leg has a big influence on the perception of the design.
In my case, I chose a circle of 680mm (27'') radius for the three legs each 120° on the total 930-1000mm wood slice (37-39'').
To make sure you like your design, grab a scrap wood, screw it together and test it by laying your quality slice on top.
Step 10: Enjoy
So this project is done. If you have any question, please leave a comment below;)
Special thanks to my master Ewald, who has supported with his workshop, patience and skills.
We have a be nice policy.
Please be positive and constructive.