Turning a Natural Edged Bowl
Turning a natural edged bowl is one way to make good use of a burl, or other interesting piece of wood. However, the process can be somewhat confusing or intimidating to those who have never done so, as well as some experienced turners. Following is the process I used to turn a piece of elm burl. As with most turning methods, there are always several approaches. This is just one of them.
This is the burl as I received it, minus a slab sawn off for a previous bowl. I had been hanging on to it for a while, waiting for inspiration, or in this case, I had a request for a specific type of turning. This was the ideal candidate.
I drew a circle on the flat face to determine the largest diameter possible, but then I ran into a bit of a problem. How was I going to follow my line? The top was anything but flat, and I wanted to turn this piece for maximum yield. As I mentioned above, there is always more than one way to approach a turning problem. I don’t know that this one was necessarily a good one, but it worked in this case. As I pondered how to saw it out, an old bandsaw jig came to mine, the kind sold for the cutting of circles in panels and such. I thought I would adapt the process to my needs at the moment.
I built a simple jig, shown here, to saw the blank into a circle. Sawing a piece on the bandsaw with unsupported wood can be dangerous, as the wood has a tendency to tip and bind the blade. I thought that if the pin were long enough, it would act as a stabilizing post for the wood. In this particular case it was successful, but I would NOT recommend it for wood that is green or soft, or of unknown characteristics. Being that this piece was very hard, dry, and solid, I felt comfortable in trying this out.
I positioned the pin to accommodate the radius of the bowl blank, and installed the wood on the pin. Sawing the blank was quickly accomplished with a minimal amount of excitement or danger. The blade did not follow my line perfectly, but I got it very close to what I wanted. The dual goals of removing the corners and retaining the maximum size were easily met.
This is what the blank looked like before mounting on the lathe. I should mention that the pin was sized so that I could drill a hole sized to accommodate my screw chuck. Usually I will mount a piece like this between centers to rough out the initial form, but in this case it seemed like the thing to do to try the screw chuck. It was a little further out from the headstock than I would have liked, but it turned just fine, and the screw provided plenty of driving force to shape the bottom of the bowl.
Here we are mounted and ready to go. Notice the difference in color between the heartwood and sapwood. One advantage mounting between centers has is that the bowl blank can be repositioned as the roughing process develops, allowing the turner to take voids and other surprises into account. Mounting on a screw chuck like this reduces these options somewhat, but I was confident that I would not encounter anything unexpected in this piece.
In this picture, the bowl has been rough turned on the outside, a tenon has been formed for the scroll chuck, and the bowl has been reversed. After truing up the outside to get the blank running as smoothly and as concentric as possible, I was ready for the next step – coring out the center. Any kind of hollowing on a natural edge bowl is exciting because of the irregular edge. Coring is doubly so, at least in my mind. It is actually safer to run the lathe faster in these instances. This minimizes the chances for a drastic catch by minimizing the amount of time the cutting edge of the tool is in air instead of wood. It also allows for a smoother cut.
Here I am coring out the center with the Kel MacNaughton coring tool. I am using the medium curve of the small set in this case. The lathe is running about 800 rpm. I suppose I could have gone a little faster, but this was plenty fast enough for my purposes. Once the core was out, I was able to turn the rest of the inside of the bowl as I would any other. The biggest difference is this: Great care needs to be exercised in the placement of the tool rest, the tool, and especially your hand. A turned rim bowl will give you a bit of a brush burn or a splinter. This thing is like sticking your hand into a moving saw blade.
Most of the time the core will pop right out as the tool hits center. Sometimes the tenon is small enough to break the core out with a tap of a hammer or teh palm of your hand. Clearing chips and checking for progress is essential in this type of turning. In this case the core popped right out with a tap.
I finished out the inside with a bowl gouge and a heavy scraper. In a lot of cases, some sanding on the lathe can be done, but again, it must be done very carefully! In any event, there is a significant amount of hand sanding that must be accomplished because of the ragged edge.
Here is a shot of the bowl so far. It has been rough turned, cored, and finish turned, and sanded as far as possible. Now it is time to reverse it once more and remove the tenon with which it was held. There are a couple of ways to do this. The first and easiest is to leave the tenon on, but it ends up looking just like that – stuck on and not belonging. A vacuum chuck is the ideal method, but in this case, it was not possible. There were enough voids and inclusions to prevent the formation of a vacuum. So, I used the tried and true friction chuck method. In this process, a scrap of wood is mounted on the headstock, and turned to fit as closely as practicable to the bottom of the bowl in question. A piece of foam backed sandpaper is inserted between the scrap and the bowl, with the abrasive surface against the work. This does a couple of things. First, it cushions the bowl, and fill any gaps between the scrap piece and the bowl. Second, in the event the bowl does slip, the abrasive grit sands the bottom just a little, as opposed to melting foam into the wood, which is messy and time consuming to remove.
The bowl is then remounted between centers, and friction is used as the driving force. At this point light cuts are required for several reasons. Fist, the rotation can be easily stopped by the force of the cutting tool. Second, the bowl can be knocked out of round by an aggressive cut, and finally, even if you are successful in applying force, a catch is the last thing you want.
Here is a closeup of the bottom. Most of the tenon has been turned away, and the bottom sanded as far as possible. It is very important to resist the urge to part right through the tenon and attempt to catch the bowl. The reason is, it is impossible. The bowl invariably orbits out of your flailing grasp and lands on the hardest, pointiest piece of metal in the shop, and that after bouncing around a few times. This process doesn’t save any time, it wastes it. A few minutes of sawing and carving have now been expanded to a couple of hours of sanding and swearing, if the piece can be rescued at all. At this point the bowl should be removed from the lathe. The tenon can be carefully broken off, or better yet, cut off with a hacksaw or other implement. The stub may be removed with a carving gouge, and then sanded smooth. To finish off the bowl, find a comfortable chair, set up a good light, and grab a stack of paper in various grits. With a little sanding, or a lot, depending on tool technique and how the wood behaved, you will end up with a very nice finished product, which will cause onlookers to marvel at how you got that wood that way.
Here are two shots of the finished product. The actual size is a little hard to define, but it is approximately 10″ in diameter and 4″ deep. It was finished with Watco Natural Danish Oil and buffed on a Beall System. I need to have my head examined for buffing it. After I got it nice and shiny, I spent a considerable amount of time picking out hundreds of tiny bits of lint from the eyes and inclusions that grabbed them out of the wheel.