Dan Forman
11-28-2011, 3:07 PM
Well, I survived my first attempt with the Mcnaughten center saver last night. I had a 14 x 5" walnut blank, and only tried to take one core, as I didn't want to take any chances with losing the larger bowl. I had watched Reed Gray's video a few times, so had some idea of what to expect. My experience was somewhat more "interesting" than those portrayed on the video however.
I started with a dovetail recess on the bottom of the blank. It was nearly 1/2" deep, with what I thought was plenty of wood surrounding it. When I got about 3/4" into the core, I had a rather nasty catch, and the blank jumped off the lathe. Inspection revealed that one side of the recess broke off, and the other side cracked. It was heavy enough that it didn't really fly so much as plummet to the floor. I had left the face plate on the front side, so back on the lathe it went, and this time a tenon was turned where the recess once was. It required some serious reshaping of what would become the bottom of the large bowl.
Reversing the blank again, I took off the faceplate, and turned another tenon on the front side, so that I would have a way to hold the smaller core, in the event that I was able to separate it from the larger blank.
Reed describes two modifications that he made to the rig. One is to drill a dimple in the tool post which locks the gate via a set screw, rather than letting it rotated as it is designed to do. I tried that, and found that I had better luck with the gate moving free. Maybe further experience will change my mind, but for now, I will let it swing.
The other modification involves putting a flat edge on the cutter, similar to the way they used to be made, rather than the point that they come with now. He reasons that the flat, scraper type edge is shorter than the pointed one, and takes a smaller shaving, 3/8" rather than 1/2", thus providing less resistance when cutting. I Started with the point, but shortly after the catch mentioned above, and many other mini catches, I went to the grinder and flattened the point. I do think this helped, and think it also makes it easier to take a little off either side of the cut for clearance.
In spite of my preparation, I still found it a pretty wild ride, lots of minor catches, and not at al a smooth process. But everyone says there is a pretty long learning curve. Reed did say that it's a good idea to start with some wood that you don't really care about, and that fruitwood like apple or cherry is a good place to start, and to avoid stringy woods like soft maple or poplar. However, I didn't have any in a suitable size, and really want to get these last few large walnut blanks roughed out. I don't know if walnut is one of the more difficult woods or not. The only other sizable pieces I have are elm and soft maple, and I know that the elm is pretty stringy and the grain is interlocked, so probably not the best place to start.
So, I ended up with a 14" fairly deep bowl, and a 9 1/2" shallow bowl, nothing broken, and ready to have another go today.
Any tips on using this coring system would be appreciated. I started at about 500 RPM, sped up to about 700 when getting closer to the center to compensate for the slower rotation at that location. I think I will stick with tenons, as I am just more comfortable with them, and the Oneway Stronghold has a very tenacious grip.
Dan
I started with a dovetail recess on the bottom of the blank. It was nearly 1/2" deep, with what I thought was plenty of wood surrounding it. When I got about 3/4" into the core, I had a rather nasty catch, and the blank jumped off the lathe. Inspection revealed that one side of the recess broke off, and the other side cracked. It was heavy enough that it didn't really fly so much as plummet to the floor. I had left the face plate on the front side, so back on the lathe it went, and this time a tenon was turned where the recess once was. It required some serious reshaping of what would become the bottom of the large bowl.
Reversing the blank again, I took off the faceplate, and turned another tenon on the front side, so that I would have a way to hold the smaller core, in the event that I was able to separate it from the larger blank.
Reed describes two modifications that he made to the rig. One is to drill a dimple in the tool post which locks the gate via a set screw, rather than letting it rotated as it is designed to do. I tried that, and found that I had better luck with the gate moving free. Maybe further experience will change my mind, but for now, I will let it swing.
The other modification involves putting a flat edge on the cutter, similar to the way they used to be made, rather than the point that they come with now. He reasons that the flat, scraper type edge is shorter than the pointed one, and takes a smaller shaving, 3/8" rather than 1/2", thus providing less resistance when cutting. I Started with the point, but shortly after the catch mentioned above, and many other mini catches, I went to the grinder and flattened the point. I do think this helped, and think it also makes it easier to take a little off either side of the cut for clearance.
In spite of my preparation, I still found it a pretty wild ride, lots of minor catches, and not at al a smooth process. But everyone says there is a pretty long learning curve. Reed did say that it's a good idea to start with some wood that you don't really care about, and that fruitwood like apple or cherry is a good place to start, and to avoid stringy woods like soft maple or poplar. However, I didn't have any in a suitable size, and really want to get these last few large walnut blanks roughed out. I don't know if walnut is one of the more difficult woods or not. The only other sizable pieces I have are elm and soft maple, and I know that the elm is pretty stringy and the grain is interlocked, so probably not the best place to start.
So, I ended up with a 14" fairly deep bowl, and a 9 1/2" shallow bowl, nothing broken, and ready to have another go today.
Any tips on using this coring system would be appreciated. I started at about 500 RPM, sped up to about 700 when getting closer to the center to compensate for the slower rotation at that location. I think I will stick with tenons, as I am just more comfortable with them, and the Oneway Stronghold has a very tenacious grip.
Dan