Ergonomic desk table top made out of solid pine
Because a simple counter top 60 cm deep is not suitable for a computer desk, I received a request to replace it with an ergonomic desk table top.
I started my work with some pine planks (4 cm thick), very nice cut, tangential. The planks cut in this way is very good, because it is resistant to bending on both it’s length and it’s width. After I planed all 8 boards on all four sides, I made the first check of the panel layout, of course with no adhesive applied.
It is a fairly wide desk table top, so my standard clamps weren’t enough. I used the clamps made last summer when I had to glue another wide table top. I had to sand them a little bit because they were rusty, but they have worked out great. I used some fir scraps of 8 cm by 8 cm in section as spacers to compensate the difference between the 85 cm of the new panel that I had to glue, to the one meter width of the old table top I made using these clamps. I could have drilled another set of holes in order to move one of the props of the improvised clamps, but I had no necessary drill bit, so I chose this improvised spacers made out of pinewood, which worked very well.
After checking the layout without any glue applied, I did some fine tuning and I rearranged the boards until I was satisfied with aspect of the panel. I then applied polyurethane adhesive. I used Hranipur 45, a polyurethane adhesive with a D4 resistance class and 45 minutes open time. This is in theory, because, in practice, you can not let it more than 10-15 minutes without clamping the pieces. Otherwise, if it exceeds 15 minutes, it will be very difficult to stick the boards so that the seam comes out well, just because polyurethane adhesive already starts foaming. So I applied one line of glue on each board, except the first and the last planks. I always let the first this way, because the polyurethane adhesive only applies on one of the parts that have to be glued. I left the last board without adhesive because, when I spread the glue on the other boards, I put the excess from every board on the last one. This way, in the end, I had almost no excess glue.
I tightened the clamps using wooden wedges and small spacers to squeeze as much as possible. After we fixed all four clamps (the panel was 1.3 m long so 3 clamps weren’t enough) so that all the boards stuck well together, I tightened the panel horizontally using four different iron bars, 40 mm by 40 mm, which I tightened well using some F clamps.
In the meantime we built a clamping system that helps us to make large panels with easy. The most important thing is that those 4 way panel clamps tighten the panel and flatten it at the same time.
When the adhesive was fully dry (because the temperature was not very high, I preferred to let the table top overnight before releasing the clamps), I removed the clamps and cleaned the hardened excess glue using the trowel that I used to stretch the adhesive (I took care to wipe the trowel while the adhesive was not hardened). I could almost perfectly clean the adhesive that squeezed out when I have tightened the clamps. The adhesive turns into a foam that hardens with sufficient air gaps so it can be easily removed.
If the panel wouldn’t have been very well adjusted when I tightened it, I would have had to use the router. But I was careful to fit all the boards as good as possible, so I didn’t have to do this step. I just passed directly to polish the table top.
When you work with pinewood, any sanding becomes a very difficult step with a lot of potential for failure. That’s because there is a big difference of hardness between the white and the darker fiber and the sanding result is usually a bumpy wood, depending on the drawing of the wood fiber. To avoid such problems, I noticed that the best sanding is obtained by pressing very hard on the orbital sander, holding it as little as possible in one place. So, with a lot of care and using circular movements, I sanded the desk table top on both sides.
Then, I took the next step: to shape the desk tabletop using the handheld circular saw. I have not used the circular table saw as the table top was too big and too heavy (although it was made out of pinewood, having a thickness of 3.6 cm, 1.3 m long and 85 cm wide, the panel came out around 10-12 kg). It wouldn’t have been too easy to handle it on the table saw, so there was a pretty big risk to cut it wrong.
After I gave the desk it’s final shape, I used a scrap piece (remaining from the step when I cut it) and I glued it on the part that will become the back of the table top, on its upper face. It is very useful for those quite frequent and annoying situations when you drop something behind the desk. In this case it will not happen like this thanks to that stopper. When the PVA glue was dry (we used PVA glue because it hardens faster), I aligned a metal bar very well which I tightened using two clamps and I made a cut with the handheld circular saw. I took care to lower the blade to make sure it would cut the entire table top (the 3.6 cm of the table top to which I had to add the 2 cm of the stop plank).
By cutting along the glued piece I was able to check the quality of the glue up, which turned out perfect. The two boards seemed to be one, without any gap between them.
After I finished shaping the table top by cutting it to the desired size and gluing the end stopper, I started to finish the edges. One of the biggest inconveniences of the old desk that I was rebuilding was that the edge was uncomfortable for the hands. So I chose to make the edges with a very large bevel, spreading to a distance of 6 cm deep by 2 cm high. I had to make a cut on the front side and 2 cuts on the other two sides. While I was planning how to make the cuts, I noticed that the two sides would have looked better with a steeper cut, so I chose to do it a little bit differently.
For the front side I used the table saw, by tilting the blade at 15 degrees and I set the parallel guide to cut the table top by holding it vertically. With a 3.6 cm width and a 85 cm height, it was practically impossible to keep the desk table top vertically throughout the cut, so I clamped a support board to increase the width, making the tabletop much easier to handle.
As I said, I preferred to cut the other two sides with a much sharper angle to gain as much work space on the desk as possible. There was no way to use the table saw because the desk back stopper glued earlier would have gotten stuck in the fence. So, using an 8 cm by 8 cm scrap piece of wood to enlarge the width, I cut the two sides using hand circular saw, with the disc tilted at 45 degrees. I set the handheld circular saw blade parallel guide to make the cuts to continue from the front side of the table top without any significant differences. I say without any significant hops because there were small differences, but I’ve corrected them by sanding the table top. I finished the cuts using the jigsaw, because of the back stopper of the desk, at the end of the cut.
The next step was sanding the previously cut edges, the step in which all the cuts had to be rounded so that the desk became as ergonomic as possible. For this step I used two sanders: the orbital one, with which I sanded the marks left by the circular saw blade and the rectangular vibrating sander which I used to round all the edges to make them as smooth as possible. I chose to use the rectangular sander to round the edges because it is much less aggressive, meaning that it takes less wood per pass, so that I could do the wood sanding without the risk to ruin something. I used fine sandpaper of 180 grit for both sanding grinders, so the final area was very smooth.
After nearly two hours in which I sanded the surface and the edges of the tabletop, when I could declare myself satisfied about the future desk appearance, I repaired the small defects of the wood (the broken wood chips or the wooden split knots) using white acrylic putty. After several hours, when the putty was completely dry, I sanded again the tabletop and I applied another layer of putty where needed (in the deeper holes, the putty would shrink and it was almost impossible to apply it in one pass only). In the end, I made the last serious sanding with fine sandpaper of 180 grit.
I colored the desk table top with water-based stain in walnut color (actually the color is called C12, but has a very similar tone to what it is found in the specialized stores under the Walnut name). I chose to use this kind of color because the so called walnut stain has nothing to do with the nuances of a walnut wood. I applied the stain with the paint gun, as it is a fairly large area, which certainly would have had traces if I had applied the color with a cloth or with a sponge. Because the pinewood is very picky, the tabletop still needed a few minor manual retouches, which I did very carefully with a small sponge.
After staining, when the stain was completely dry (which lasted several hours due to the cold weather outside which translated into a lower temperature, about 16-17 degrees Celsius in our workshop) we applied a thick layer of polyurethane primer, using the spray gun.
I left the desk tabletop overnight, although, at a first glance, the primer seemed to be dry, just half an hour after application. The problem was the sanding of the primer, when you get to the layers below, layers that are not thoroughly dry and there is a risk for the primer to peel or to stretch. The next day, when I was sure that everything is completely dry, I sanded the desk with the orbital sander (using the lowest speed, very carefully and with 320 grit sandpaper). I chose manual sanding for the edges which, although it is more difficult to do it in terms of effort and in terms of time, it is safer (there is no risk of completely sanding the primer). Even so, using the manual sanding with sandpaper of 400 grit, I still managed to get to the bare wood in two small places. I corrected these spots, staining them with a sponge.
After I thoroughly cleaned all the dust from the tabletop, I applied the polyurethane varnish. I used a special polyurethane varnish, with a light gloss degree (20%), but with a high resistance to scratching, which is ideal for the desk. Besides the resistance to scratching of the varnish, the polyurethane primer penetrated pretty well in the wood surface and gave the wood increased mechanical strength, which will make the office even more enduring.
The final part (which is always the most enjoyable, because the results of your work are seen) was to install the legs bought from Ikea. I screwed the legs with the 25 mm long screws included in the package, so there was no risk to penetrate the desk table top too much, because its thickness was 36 mm. However, I chose not to screw the legs in the front, where the edge was bevened, because there was a risk that the screws to penetrate completely through the front and out of the tabletop.
The result was an ergonomic desk table top, very comfortable for the hands, regardless of the position you sit, with a large work surface and a high resistance (for a piece of pine wood furniture).
But the most important result was the customer’s satisfaction, who was extremely pleased with the ergonomic desk and the quality of the finish.