Coring out Bowls with the Kel McNaughton Coring Tool
One of the best ways to maximize your turning pleasure is to core small bowl blanks out of larger bowl blanks. This serves several purposes. First, it saves wood, which is important whether you buy your blanks or harvest them by the sweat of your brow. It saves work, in that you don’t have to sweep up and haul away as many shavings, and thirdly, it saves time, because you can core a bowl center a lot faster than you can turn it into shavings.
In the not too distant past I hosted a small gathering of turners for the purposes of demonstrating the Kel McNaughton bowl coring system. It was not a large gathering, but we had some fun, and for the edification of you who could not make it, we took pictures.
The whole thing arose because Mark Mandell, a student and fellow turner, is (was) waiting for the delivery of his Stubby 1000 (he has it now). He wanted to be able to core some bowls out of the huge trees he is finding, so I invited him up for a demo of the tool. In addition, Bill Lownes, and Bob Berner, both local members of our AAW chapter also appeared for the event.
Here I am rounding a piece of Chinese elm supplied by Bill L., I ended up with a bowl blank approximately 16” in diameter and 7” deep. It would have been closer to 18” in diameter, but a defect in the wood required a smaller diameter.
Setting up the tool is fairly straightforward. While it takes some practice to get the hang of coring, there are some objective parameters to observe. First we marked the blank so that the outer piece would end up being about 1 5/8” thick, or close to 10% of the diameter. Then, we set the height of the coring tool. It is essential that this part be done properly. The tool must be set up so that the tip of the tool remains on center when the back of the tool is fully engaged with the gate on the tool post. Improper setup here is the source of the misconception that the tool requires brute strength to operate.
Once the height was set, we determined which knife would give the largest core while preserving the integrity of the largest bowl. Regardless of whose coring tool is used, it does no one any good to get a beautiful core if the outside blank is ruined in the process. This process is somewhat subjective. Results improve with practice. Different sized blanks can be cored out by changing the angle of entry as well as changing the knife being used. My method is to look down on the bowl blank from above and visualize the angle of the knife as well as the curve being used.
Here I am coring away. As you can see, I am not holding on for dear life. The knife is set approximately 12” out from center, and the lathe is turning at 750 rpm. The higher rpm of the lathe makes for smooth cut, contrary to some assertions I have seen that a slower speed is necessary. Here the second myth of the difficulty in using this tool is dispelled. One does not need a huge motor to handle the forces generated by the tool. One needs a light touch and patience. Now, of course, I don’t need them for my Poolewood, although it is possible for me to stall the machine by being too aggressive. A light touch, a bit of patience, and backing the knife out regularly to remove clogging chips all contribute to an easy and non frightening coring experience. Even taking my time and posing for the camera, this process took less than five minutes. In regular use, I can core out a bowl of this size in less than five minutes including setup time.
Here we have the core out, nice and smooth. This will make a 12” (rough) bowl, a little more than 4” deep.
In this final picture, we see secret agent Mark Mandell coring out the core to produce a third bowl blank from one chunk of wood. Oh yeah, one other thing that helps the process along is lubrication of the knife. A good friend of mine uses water, dipping his knife periodically into a jar of water. I get good results spraying the knife with some WD-40. If anyone has any questions, please feel free email me. I have no affiliation with Kel McNaughton beyond being a very happy customer.