How to make a thick oak wood tabletop
I recently had a customer that really liked the way we build a thick oak wood tabletop. He saw on our website one of our coffee tables and he liked the way its wooden top looked. The top was made from oak wood, with continuous lamellas. The boards were also wide enough so the surface of each one could easily be noticed.
After settling with the customer on the way the tabletop should look, we agreed on a thickness of 4 cm and I started the work.
I had to drive a couple of hours to buy some beautiful oak pieces, around 5 cm thick and 1,1 m long. I have to admit that they were pretty cracked in the middle, but that’s the way the local oak is, so I couldn’t do anything about it. Because of the cracks, I had to buy more wood than needed, to make sure I wouldn’t have to drive 50 km again for another small piece.
I did a little re-saw on the planks, to ease the jointer’s work and to save some wear on the knives.
I then moved on to the step where huge changes happen: flattening all the boards on all their four sides. As I planed them, I placed them next to each other, until I reached the desired width for the tabletop, 75 cm to be precise. Why 75 cm? Because the tabletop had to be 70 cm wide, but I added a safety margin, to be able to make slight adjustments before gluing everything.
With the necessary boards prepared, I found that I had 2 pieces left out of a total of 7, meaning that I bought around 40% more. After all, it’s not bad, because I still have a few small things to make out of oak.
We started matching the planks, paying attention to defects on the ends, which were not allowed to be in the final tabletop, and to the grain of each plank so that the final appearance would be as beautiful as possible.
After matching the boards, I drew some lines to guide me in cutting each plank. I chose to cut them at 83 cm for a final length of 80 cm, to avoid small defects on the ends of the planks, usually caused by the planers snipe. Unfortunately, the large planer is not perfectly tuned and still leaves little snipe on the first and last 5 cm. With a bit of luck, I noticed a crack hiding in one of the planks and I was able to rearrange it before cutting the board. I erased the first pencil marks so that there is no risk of making a wrong cut. Before I moved them from the table to be able to use the saw, I took the time to name each of them, so that I can keep the chosen order and pattern.
After cutting the broken or excess ends, I had to do something I did not really like, but I couldn’t get away without it: I had to set up the planer, in order to be able to fix the imperfect edges. That was also the time to plane all the boards at the same thickness. I made them 4.4 cm thick in order to leave a margin for straightening the panel after the glue dries.
I put everything back and searched for possible spaces between the boards in the center of the panel, in case there were concave curved boards. It was not the case, but I saw some spaces on the ends, which meant a convex curvature. I tightened one of the ends with a clamp and I noticed the distance at the other end of the panel. If it is 1 – 1.5 mm, it is not a problem, it can be corrected by tightening. But at one of the joints, the distance was more than a few mm, so I had to make another pass through the planer.
After all the necessary fixes, I thanked myself for leaving a margin and I moved on to gluing.
For this tabletop, a clamping force of approximately 2150 kg (6 kg / square cm, as stated in the polyurethane adhesive instructions) was needed. I have calculated the force of a clamp to about 500 kg, so because of the fact that I only had 4 functional clamps, I concluded that it is not a problem if the total force is somewhere at around 2000 kg as long as the boards are squeezed tight.
I spread the adhesive, using a trowel so that it covered the entire edge of each board (I forgot to take pictures at this stage, but it is obvious that it was well spread by the way it dripped on the sides) and I tightened the panel with the four clamps. Besides these clamps, I used beech runners to correct the positioning differences in height. At 11 o’clock I tightened the last clamp and left the panel to stay until the next day since on the adhesive bottle it clearly states to avoid any machining for 8 hours after tightening.
After some years of using this method, we designed and made our custom 4-way panel clamps, in order to reduce the time spent with tightening and flattening an oak wood panel. You can find here the free plans in their dedicated post.
A new day, a new step – the most enjoyable: turning a bunch of planks into a real tabletop.
I removed the excess glue with a very sharp spatula (it cuts similar to a chisel) and I did a few passes with the orbital sander using a coarse 50-grain sandpaper.
The countertop came out very well, except that when moving my hand over it, it felt a bit uneven along a couple of the joint lines. So I took the router and used the new straightening jig I had recently done. Although the pictures seem to show very large differences between the cuts, they are very small and after another pass with 50 grit sandpaper, everything was as level as it should be.
Another step (I also forgot to take pictures at this stage) was the cut to the final size. I used a piece of melamine board with two perfectly straight edges, cut at 90 degrees, and a handheld circular saw.
I have agreed with the customer that the edges should be rounded on top and beveled on the bottom. Besides the aesthetic reasons, since it was going to become a table, it is important that the edges are not sharp, to make the finish last as long as possible. For rounding, I used the router with a roundover and beading router bit, but for the beveled edges on the bottom, I only had to use the vibrating sander, with 40 grit sandpaper on it (it acts just like a rasp, but with a textile backing).
After finishing with something intermediate, that is 120 grit sandpaper, I moved on to the knots and small cracks fixing. I used a homemade putty, by mixing a water-based lacquer and the sawdust left from the initial sanding. You might ask why I did not use other planks if there were cracks in the ones that I chose: Because there were only small surface cracks that did not enlarge even in the temperature variations caused by sanding. But the main reason was the beautiful grain on these boards. Considering the high elasticity of the putty I used and the polyurethane finish, I’m sure nothing will happen. However, I told the customer that if a crack somehow shows up over time he should let me know and I would fix it right away. (It’s been over two years now, and the tabletop seems to be still in great condition, so I was right about these cracks).
I let the putty harden until the next day when I made some small corrections where it was needed (at one of the knots on the back, where there was a very large volume of putty that I had to add, some small corrections were needed).
The final finishing followed, with fine 180 grit sandpaper, which gave the tabletop such a perfect look, that I almost didn’t want to spray it anymore, in order to not change its beauty. I don’t know how much you can see in the picture because the workshop was a bit dusty, but it looked great:
But a deal is a deal, so I moved on to the spraying phase: I washed the gun with some acetone (it is called D1016, but it’s 99% acetone, and it smells horrible, even when wearing a pretty good half face mask). Then I mixed some creepy substances with an equally horrible fragrance, that is polyurethane, hardener, and thinner, D1010. Because it was very nice outside I moved the countertop on the balcony and sprayed a pretty thick primer layer. This way I avoided all sorts of stupid methods of ventilating the room and moving the compressor elsewhere so it would not blow up due to the vapors caused by spraying.
After a few hours, when the primer had hardened, I made the final sanding: using the orbital sander and 320 sandpaper for the top and also 320 grit sandpaper for the edges, but using only manpower to avoid a too deep sanding. I took care of the primer to be hardened really well since if it is not completely hardened, the sanding will result in a mixture of dust, something sticky, and small bits of sandpaper. This combination might make you start over, which meant that I wouldn’t be able to deliver the counter in time. I was relieved that everything went well with the final sanding, so I prepared the other substances (also with a lot of “perfume”, obviously): a special scratch-resistant, with a 20% gloss level. I applied it in a thick enough layer to withstand the wear, but not too thick, in order to avoid drips that would have ruined everything.
After another two to three hours of hardening, and with the help of the baking paper (since the top was pretty heavy, there was a risk of damaging the finish while transporting the top), I went to meet with the customer. I handed him the tabletop, along with the instructions: “Do not use it until tomorrow”, “Do not put it on anything before covering it with baking paper” and “Take care, it’s pretty heavy!”