This is not for the faint of heart.
Taking a log, and turning it into the torus bowl is not a beginners project, it takes a wide set of skills which takes a long time to hone to a level good enough to make this bowl. Please, if you don't feel your skill level is at the right place at the moment, do not try this at home, but if you are at a stage in your turning career where you think this is something you can produce, making a successful attempt at this bowl will bring you great personal satisfaction.
In this project we will be using an Oak half log which has been cut, sealed and left to dry for over 4 years. The reason for using a dry log and not a fresh one is that this project can take so much time, that the blank on your lathe will distort and change shape while you turn which will cause it to either crack, or simply end up uneven.
I hope you will enjoy this, my first instructable, of many more in the future.
Step 1: Marking and Cutting Your Blank
Using any type of tool that you have in your shop for marking out bowls, be it a compass, or a center finding jig like the one I'm using in the picture above, mark the confines of your bowl, but remember to take into account the shape of the bowl, if your log is too narrow, you won't have enough thickness for a fat, rounded, bowl, but you could still make a much harder (for reasons we will see ahead) thin and wide torus.
Cut your log using your preferred method, I use a chainsaw, a lot of people use a bandsaw with a circle cutting jig or by hand. There are those of us with skills so great they can chop the circle out using an axe.
Step 2: Fixing Your Blank to the Lathe
This step should be known to anyone who ever "chucked" a blank to his/her lathe, but it's important we go over this as there are many different way to do this step. I am going to show you my method of choice, and I would recommend it as it will give you the freedom to work on this project properly, although I can't say other methods will not work just as well, it's a matter of habit and preference.
Drilling a hole in the center of the blank (which we marked before cutting the blank) using a hand drill or any other drilling device will prepare the hole we will use to mount the blank to the lathe using the woodworm screw (I believe the name "woodworm" is owned by Nova, but each chuck has a similar screw).
Screw the blank tightly onto the screw that you have placed in your chuck, and close it off using the tailstock as support, this is a rough blank and the lathe will shake while we turn this blank to round, we don't want it flying around the shop!
Step 3: Turning the Blank Round and Marking for Size
Taking your tool rest as close as you can to the blank without hitting any corners is crucial for working safely on the lathe, the closer the tool rest to the piece of wood, the lesser force you need to keep on the tool to counteract the cutting forces coming from the spinning piece. Use your favorite roughing tool, you can use a scraper, your spindle gouge, but the preferred tool for the job by far is the bowl gouge, and turn the blank round. Don't forget to push your tool rest closer to the piece as you turn away the material as the gap between those two will increase.
Once round, using a pencil, mark out the width of your to be bowl. Take into account the fact you are going to turn a torus, so this measurement will not only determine the height of your bowl, but also the width of the "body" of the bowl. Making this height measurement larger than half the width across the face of your bowl will result in an impossible shape, making it exactly twice the width will create a closed form torus, and making it larger will create an open torus, or a doughnut shape, which is what we are aiming for in this project, but feel free to experiment!
Step 4: Parting the Excess
Using a parting tool, part off the excess wood, but don't go all the way through, or else you might have a spinning disk of wooden death flying around the shop. Stop when the center is still a couple of centimeters wide and finish the parting using a saw. Bring the tailstock back up to the wood and fix it in place.
Step 5: Measuring for a Template
Measure the width of your soon to be bowl, and cut out a cardboard (or plywood, or sheet metal) template of half a circle with the same width as your bowl. We will use this template throughout the project, so keep it somewhere you won't lose it among the shavings or shop clutter. since the body of our torus is a circle all around, we need just the one template for the whole process. We will also cut the sides of the template thinner in width so it could fit into tight corners, as you will see later on along the process.
Step 6: Shaping and Sanding the Outside
Using your spindle gouge (or bowl gouge, just as fine) round off the corners of the blank, in effect creating a large bead from the side of our blank. Work slowly, checking often with your template to make sure you keep the shape true. Use your flat nose scraper to smooth the transition between the curves, and once your curve fits the template perfectly, stop, or else you will be taking off from your bowl overall width.
Finish this step up by sanding the curve you just created smooth. You don't have to sand it to a finish, just use 60-80 grit sandpaper to smooth the surface up uniformly, this will shorten sanding time later.
Step 7: Shaping Half of the Internal Curve
This (and its counterpart on the other side) is the most important part of the whole project. Getting this part wrong, or not accurate to a millimeter means your two torus halves won't connect and won't transition one into the other. I can not stress enough the importance of getting this step right.
Using your template mark the high point of the inner curve. That would be at the top of the "leg" of our template, but only when the template is held at a perfect right angle to the plane of the bowl. That point is the "high" point of the curve, or the top of the curve, which we will create.
Measure and mark a second line at a distance equal to the radius of our half circular template. That will be the confine of our would be curve, and it also marks the low point of our curve. Now that we know the point to which we need to curve to, we can use our parting tool to clean out some material in a groove OUTSIDE of that line (toward the center of the form). Take special care not to part into the wood to more than half the width of our curve, as this means that when you will be cutting the same curve from the other side, you will part the bowl before you are done. So if our curve is 6.5 cm wide (like on my bowl), I don't part the wood here to a depth of more than 3.25 cm, I will part it to 3 cm, and so I'll know that when I will finish this curve, and the one from the other side, I will have a 0.5 cm membrane right at the center of the form still holding the bowl to the center of the blank which will remain on the lathe after I part the bowl off.
Using your spindle gouge (or bowl gouge) cut the curve away, using the template to check and see that the curve you are cutting completes the outside curve (by sliding it from the outside in along the curve). Take it slow, one fraction of a curve at a time, especially if this is the first time you are cutting this type of curve, or if you never made a perfect sphere,which will be a perfect exercise for this kind of project.
Finish up this side by sanding the face of the curve to bland it into the outside curve, and this time sand the face and outside to a finish grit (I sanded it down to 1000, and then applied pressure with shavings, burnishing the wood).
Step 8: Hollowing the Bowl Out
This is a pretty much straight forward part, using your tool of choice, mark and hollow out the forming doughnut form, just remember that one of the "corners" of the form is still not shaped on the outside (the inner curve opposite the one we did in the last step).
In my case, I used a parting tool to mark where I want to have the opening, then used a spindle gouge to scrape a cove I could use to hollow from, then using a couple of hollowing tools (angled and straight) I emptied out the form. When you are done, use sandpaper to sand the inside smooth. People will hold this bowl to their faces to admire the shape, so you better not be lazy and sand it up really well, every tearout and scratch would be visible once you apply a finish. When sanding inside, watch your fingers. I have friction burns on 8 out of ten fingers, and more than once my fingers got caught in the small space inside the form and I was lucky they didn't break. If you're not comfortable doing this, consider making a larger opening, but you will still need to have nimble fingers to sand this inside part properly.
Step 9: Applying a Finish to Inside and Out
In this case I chose to use beeswax as my finish, I find seasoned Oak, with its large porous grain and deep browns profit from a natural finish as beeswax. It is also a finish you can scuff up with a high grit sand paper if you decide you want a matt finish, yet still have all the pores filled in and closed up. In fact I chose to do just that in this project. You can always change your mind, find a way to mount the bowl back on the lathe and give it a shining buffing.
Using a piece of hard pure beeswax, I apply the wax to the wood, inside and out, by dragging it over the wood in low speed. once I feel the whole bowl is covered, I turn the speed up and using a folded up paper towel or a small cloth rag I apply a small amount of force to the surface of the wood, causing the wax to melt. Running my hand along side the curves of the wood, more wax is melted and is spread around the bowl. Any excess wax will remain on your paper towel or rag.
Step 10: Turning the Blank Over
After finishing applying the finish to the bowl, you should twist off the bowl off of the woodworm screw. Now you can use the stem that we left at the center of the form to chuck the bowl on the other side. Note that at this point this shaft doesn't have a shoulder to rest against the chuck jews, so be extra gentle with your cuts. You could also pre drill a hole in the center before you turn the bowl over and use the woodworm screw, but drilling a perfect hole in the center of the form is difficult and might result in a little off center bowl.
Using your spindle gouge or bowl gouge, or even a scraper, turn the face of the bowl (which is actually the bottom of the bowl) flush, in preparation for completing the last curve in bowl, and the most crucial part of the whole project.
Step 11: The Last Curve
Now we repeat the same steps as we did on step 7, we mark our "borders", we part the central shaft (to a point), and we round of the last "corner" of our torus bowl.
In this part you can finally see why it is so important to get everything accurate to the millimeter, since when we are done here, and we will want to part off the bowl from the leftover stem, if the curves of both sides of the bowl don't meet, you won't have a perfect torus, and if you were really off, not even a not perfect torus. Use your template every few cuts to be sure you are shaping the curve right. If you do it correctly, there is no reason why the sides shouldn't align.
Step 12: Cut Off Preparations
So we're almost done, we've made it this far. From here on end, it's all a technicality, and a little bit of luck. Before we can part this bowl off and finish it up, we need to do two quick steps. The first, as you can see, is drilling a small hole along the shaft to pierce through to the other side. We do this simply because in this example I am going to part the bowl while it spins on the lathe. You can choose your way of parting, you can drill holes all around which will part the bowl off, you can drill a couple of holes through the membrane and saw the bowl off, I didn't want to risk those things, I chose the high blood pressure choice of parting it on the lathe, but I do not go blindly into unknown territory, so through the hole I drilled I can measure how thick my membrane is using a caliper's depth gauge. Just poke it through, take a look from the back to see when it comes through the hole, and you can tell the depth. I'm using a hand drill since I had it hanging on my wall and I never used it before, it was handy and there. Else I would have used a normal power drill. When the hole is done, apply a beeswax finish over the new curve like we did before.
Step 13: Parting the Bowl Off
This part can go in two directions, should you choose to do it as I did. You can get a nicely parted torus bowl in your hand, or you can get a torus bowl jigsaw puzzle. Work slowly, in small steps, check the width of the membrane often, know when is the point the bowl will detach and be ready for it. As you can see in the images of this step, I kept scratching at the membrane with my parting tool until it was very very thin, and as soon as I felt the bowl starting to wobble slightly, I put down the tool, switched off the lathe, and gave the bowl a small twist, which parted it completely off the stem. Success!
If you choose to part this bowl using a small hacksaw or maybe by drilling holes all around the stem, this step is redundant for you.
Step 14: Finishing Touches
Well, you've made it this far. The potential for damage or a catastrophe has just dropped from 90% to 5%-10%, depending on your Dremel skills. Using a small sanding drum bit I cut off and smooth the inner curve of the torus from leftover membrane, and then painstakingly hand sand the inside rim from 80 to 1000. It is at this point I change my mind about the finish, and I sand the whole bowl over with the 1000 grit sandpaper to cut down the shiny wax finish, leaving the bowl with a matt finish, which I find much more rustic and earthy, a nice contrast to the highly evolved geometric shape represented here.
Step 15: Admire Your Work
You have made it!
Congratulation in creating one of the most beautiful of all whole form single piece bowls there is (in my personal opinion).
I hope you found this instructable as enjoyable as it is to make one of these bowls, and I hope it helped you in achieving this stepping stone in skill and passion.