Coring Bowls, my story:

After woodcutters in my neighbourhood cut down two large walnut trees, I  did not want to turn the beautiful wood I managed to salvage into shavings so I decided to purchase a coring system. After looking at the three systems on the market. Oneway, Woodcut and Kelton.
Woodcut was too small, Oneway was expensive for my lathe.  I purchased a Kelton Jumbo which appealed to me because it looked simple, relatively easy to set up and would handle large bowls. On my second try - first on walnut - I ruined one of the bowls because I was unable to estimate the correct entry angle.

Here is what you do not want. A funnel instead of a bowl.

This happened because I had not left enough wood at the bottom when I cored out this walnut blank. Fortunately this was not the biggest bowl but the next to biggest. It is important to start the cut at the correct angle so that the coring knife finishes at the correct depth.

I am sure this comes easily to those who have used this coring system frequently but I needed some guidance as I was starting out. Though I watched the Mike Mahoney video it was still unclear how to estimate the entry angle.

So here follow different ways to estimate the correct entry angle.

	Measuring Technique To calculate the entry angle I made up this half circle on Bristol board with the same radius as the coring knife. Cut out the template with some scissors so that it can be held up to the wood. You do not need a complete half circle. A quarter circle is fine.
	Draw some chalk lines where you want the knife to enter the wood. Measure the total thickness of the blank. Hold the template against the wood. In the photo I have marked a 1 on the template for where the knife will enter for the first cut. Since I have 5 1/2 inches of blank and want to leave 1 inch for each core my first cut should be 5.5 – 4 =1.5 5.5 is the total wood thickness, The four is obtained by adding the three 1 inch thick bowls you wish to core out plus the three  0.33 inch cuts. (3+3 cuts of .3 inch each) So My first cut should be 1.5 inches deep.
	If I enter the wood at the angle generated by the template in the picture above I would be too shallow. So I angle the template slightly as shown in the picture to the right, this increases the entry angle as you can see by this photo. Compare the angle of the knife to that next to the # 1 drawn on the template, and you can see that I have increased the angle by about 10 degrees. The bowl generated by this cut will be slightly conical of course. I obtained this angle by moving the template so that the line down the center of the template is slightly angled. An imaginary line drawn through point  #1 and 1.5 inches on the center line will be parallel to the face. Holding the template to the face at this angle will generate the correct entry angle. To explain this further imagine using the straight cutter which would generate a perfect cone. If you made a conical  (triangular) template in the same style as this template, you could apply the same principles.
	Here the first solid core has been removed and I have started on the second piece. The entry angle was increased by the same amount over that indicated by the template thus creating a blank bowl with a uniform wall thickness. For my lathe a back and forth rocking motion seems to help the knife enter the wood without jamming in the groove. However it is important not to pull on the handle but try to push the knife into the cut. Pulling on the handle causes the knife to jamb in the groove as it does not follow its own curve.
	Using the outside curve technique. Use the outside of the bowl to establish the initial angle. This works well if the coring knife has about the same curve as the bowl exterior.
	Using the inside curve technique. You can also make a small hollow in the center of the bowl to be cored and use the angle created at the edge of this depression to establish the entry angle.
	this shows the entry angle as established by the hollowed center of this bowl but with the tool holder moved to the entry location.
	Some examples. Just in case you need a concrete example. Here is a maple blank. Total thickness 5.5 inch I will make three bowl blanks and one core (I drew an extra line but ignore that as there was not enough room to make it.)
	Here the ruler joins the point on the edge to the 1.5 inch deep mark.
	Use the adjustable protractor to get the angle described by the tangent to the circle at the intersection of the ruler and the circle and the ruler held parallel to the face of the bowl.
	Transfer the angle to the Kelton knife entry angle.
	The core has been removed.
	Checking the calculations and I am a little over my estimated depth but by less than the width of the cut. So all is still good.
	Another bowl but a deeper one (6 1/2" thick bowl blank.). The first cut will be 3 inches deep and lined up with the inner circle.
	Here is the entry angle as described by the tangent at the blue smudge and a line from that to the 3 inch depth. So I hope you have found these instructions useful and thus have reduced the number of inadvertant funnels in your stodkpile of drying forms.

I do like the coring process as it is faster than carving out the whole interior and one gets to keep the wood for more bowls. I now have the jumbo set of cutters plus the most curved of the standard set. When using the standard cutter the holder height has to be adjusted from that needed for the jumbo set.