McNaughton Center Saver System

[cwearing]

Two questions regarding the use of the Kel McNaughton center saver system:

1. How do you estimate the depth of a cut to ensure you don't go through the bottom of the outside bowl?

2. How is the mini McNaughton adapter kit to be used?

 

[George Van Beynen]

I would suggest you get the Mike Mahoney video on coring (http://www.bowlmakerinc.com/video.htm), it is worthwhile if you have the set.

When I want to be safe I use the blade with the smaller profile than the outside profile of the bowl. Usually I use the blade with the same profile and adjust the gate by eye. One fellow had a good suggestion to make a toolpost extension high enough to mount the gate, insert the blade and look down on the bowl to see the blade path. If I was doing nested sets I think I would make one to allow me more bowls per blank. I have heard of others mounting a laser to the blade at the handle. I think practice is good advice.

My set came with the new toolpost so I did not need any additional adapters for the toolpost. The kit did include a bushing that set between two posts to elevate the mini knives, perhaps that is what they are referring to?

Good luck, if you are ever in the Mercer area let me know and we can core a bowl or two!

 

[hockenbery]

The link below is to an article written by John Hartge on a demo given by Margaret Lospinuso for the Chesapeake woodturners several years ago. It includes a diagram and method of planning the coring cut.

http://www.hockenbery-woodturnings.com/CoringwiththeMcNaughtonCentrerev.pdf


happy turning,
Al

 

[Don Snethen]

Here is a suggestion for your No. 1 question. Make a tool post extender and position the center saver knife above the blank. I made mine out of steel since I happened to have one inch rod and one inch tubing on hand, but you can turn one out of wood, perferably hard wood. Make it long enough to raise the center saver over your largest possible bowl. You might have to stand on a bucket or something to get high enough above to look down on the knife's projected path. Once you have the position you want lock the banjo in place and then remove the extender and you are ready to cut. I find that the curved knife wants to drift slightly deeper so I allow a bit more bottom thickness to avoid thin bottoms. I have not yet reground the tips on my knives to the shape that Mike Mahoney uses but understand that it helps.

Don from Eugene, OR

 

[George Van Beynen]

I have not yet reground the tips on my knives to the shape that Mike Mahoney uses but understand that it helps.

Don from Eugene, OR

Don, I was told that the new grind is better for burls as they cut to a center point. This solves some of the problems with the bottom nib pulling out of the blank. In regular grain I cannot see a difference.

George

 

[woodman]

Hi I just bought the mini set , I wanted the standard but LV were out till Oct.I bought the dvd for it first and watched it many times. I should mention that the wood that the bowl is made of is Cocobolo, I guess I should have pick a different wood to start will but the bowl that I was commissioned to make is crafted from Cocobolo. All I can say is that I have never sweated so much useing the center saver, I was so nervous it was jumping all around. I should have made the the dovetail tenion a little bigger and I think it was going a bit to fast. Tks Mark

 

[robo hippy]

Estimating the depth of the cut is always a problem with the McNaughton, and some guess work is involved. I never went through with the drawings, and meausrements before coring. I would hold the blade up against the outside of the bowl to compare the shapes, and then would hold the blade up over the top of the bowl and gate to where I planned to have the blade cut. This will also give an idea about where you want the cut to go, and how deep your blade will be cutting. Now, I seldom do this as I have cored several thousand bowls, and it is kind of automatic. I did develope the habbit of aiming a bit shallow. It seemed that most of the time I would either go too deep, or too shallow, and seldom perfect. Now, I have the laser pointer that McNaughton makes, and it helps a lot. I did modify it to make it work better on my cores. One other way to know when you are getting closer to the bottom is that there is a point where you go from shavings to chips, and it actually feels like some thing is pulling the blade in.

As far as point shape, I think Don has the old style blades. These had a bevel shape towards the outside of the cut. The bad thing about these blades was that the cutter wasn't centered on the blade, it is flush on the inside, and wide to the outside. This made it almost impossible to take a corrective cut to the inside if you were aiming too deep. The newer points are spear pointed (a Mike Mahoney idea) and the blade is centered on the cutter. I find these a lot easier to use. From my experimenting, the actual cutter profile makes no difference in how the blade cuts, or tracks in the cut (stays on the intended path). I have done bevel to the right and left, spear, and square. I have all mine ground square. The idea of the spear point is that when coring end grain, crotch, or burl woods, it is safest if you cut the blank all the way off. With flat grain (normal bowl orientation), I will cut down till there is about a 1 inch tenon on the core, then break it out. You don't have to bend over to pick it up off the floor, and don't have to worry about rolling objects going wild around your lathe. With the others, since the grain doesn't run flat, if you try to break them out, you can rip right through the bottom of the outside bowl. The spear point does work a little better for cutting the blank all the way off. The square point presents a smaller cutter to the wood (on the standard sets, you go from 1/2 inch wide to 3/8 inch wide, but the kerf size remains the same).

I also have a DVD out on using the McNaughton, and if you are interested, you can contact me.

robo hippy