In this Oneway Coring System How To article we are going to cover the steps to core out multiple bowls from one initial bowl blank.
So you’ve gone through the process of determining what Oneway Coring System components you need for your lathe, and you’re ready to get started. What’s next?
How do I use the Oneway Easy-Core Coring System?
Here’s a basic overview of what we’ll cover in this article.
You need to determine the size of the bowl(s) you want to core from the largest bowl and determine which Oneway Knife Set(s) to use.
Once the bowl sizes are determined, the Oneway Base Set needs to be positioned precisely to accommodate each bowl coring cut.
With the Base Set and Knife Set in place, the coring process begins. Take your time and keep the lathe at slower speeds than usual to prevent any binding.
Remember the Cutter tip needs to stay sharp. If the cut becomes more difficult or more dust is flying than shavings, stop and sharpen the Cutter tip.
Oneway Easy-Core Coring System Getting Started
Obviously, the above explanation is very simplified but briefly covers what we will be going over in great detail in this article.
The Oneway Coring System is easy to use once you understand the basic principles and how each knife set cuts a bowl blank from the core of a larger bowl.
Please realize, like everything in wood bowl turning, there are more ways than one to reach the same end results. I will be sharing with you the techniques that work for me.
If you use or find alternative ways that work, that is perfectly fine, and I would encourage you to share them in the comments below.
Bowl Blank Base
The large main bowl that will be cored is best turned with a few things in mind.
First, we want a strong chuck connection, and we want to avoid making the bottom too thin. The way I deal with this issue is to create a well-formed tenon and leave a wide shoulder above the tenon.
The tenon with a deeper shoulder will offer additional material in the event the inside cut becomes too deep, causing the bottom of the bowl to be too thin.
This first step is just a precaution, and after you’ve cored a few bowls, you will not need any added “cushion” at the base of your bowls…in an ideal world. Ha!
Bowl Blank Shape
The shape of the bowl needs to be considered when preparing the bowl blanks to be cored with the Oneway Easy-Core Coring System.
A hemispherically shaped bowl blank is ideal. However, you can make the bowl blank a bit wider or narrower as needed. You are not restricted to just a half-round sphere shape.
Each Knife Set will make a coring cut that is a quarter of a sphere, but the cored bowl will be shaped depending on the angle the knife is adjusted.
A cored bowl can range from tall and skinny, half circle, or a bit wider, all based on how we adjust the Base Set position and the knife cutting angle.
Best Wood For Coring
I have cored many different types of wood with the Oneway Easy-Core Coring System and have had various results.
As I’ve mentioned, like a broken record, every tree species will turn differently. Experiment and determine what woods you like to core better than others.
I’ve found that green (wet) black cherry wood cores very well and is easy on the Cutter tip. At times, with one sharpening I can core out two bowls from a large cherry bowl blank.
Dried hickory, on the other hand, has been a nightmare to core. On one occasion, I needed to sharpen the Cutter tip five times before completing the first cored bowl.
You will learn quickly which timbers core the best. Don’t be discouraged if one type of wood is giving you troubles; try a different species and keep going.
Purposes For Coring
When I first explored the idea of coring multiple bowls from a single bowl blank, I fantasized about making dozens of nesting bowls from a single bowl blank. I’ve learned that’s not very realistic.
While it is possible to core nesting bowls, the coring process is a bit crude and not as precise as I originally imagined.
The width of the Cutter alone does not allow for snuggly fitting bowls, and for a good reason. The Cutter needs to be broad to aid in the expulsion of shavings as you core.
I needed to set the idea of rows of interlocking nested bowls aside. The process of coring and making multiple bowls from one blank is still exciting and super efficient.
The reasons I core bowls is to get more yield from the wood I have salvaged, reduce waste, save time, and basically create more bowls.
Green Coring Twice Turned Bowls
Because green or wet wood is the easiest wood to core with the Oneway Easy-Core Coring System, I make oversized bowl blanks to dry and twice turn.
Twice turning is the practice of turning a rough bowl blank once, letting it dry then turning that blank again to its final size. Read this article to learn all about the details of twice turning wooden bowls.
Since the green bowl blanks need to be wider when first turned to allow for shrinkage and shape-changing, we have more wiggle room when making measurements and coring cuts.
Preparing the Bowl Blank
Turn and shape the bottom of the large bowl blank and make the outer bowl shape close to spherical. You can make the form a bit narrower or a touch wider, but round works best.
Form a solid tenon on the foot and make the added shoulder mentioned earlier.
When the tenon and outside shape is complete, turn the bowl blank around and mount it securely in a four-jaw chuck.
Take your time and level the face of the bowl with long bevel-supported push cuts until the face of the bowl is flat and smooth.
Now the bowl blank is ready to be measured and marked for coring.
Face Measuring the Cored Bowls
Because the bowls I will be extracting are green or wet, I need to make the wall thicknesses of each bowl about 10% of the overall bowl diameter.
In this example, I will be working with a 15-inch bowl blank. The wall thickness of the largest bowl, which is 15” in diameter, needs to be about one and a half inches wide, or 10% of the bowl diameter.
Using the tool rest, I will make a mark 1.5” in from the outer rim of the bowl blank. Rotating the hand wheel on the lathe, I can draw the circle of this cut location.
Next, I will measure the next largest bowl to core from inside of the first bowl blank. If the main bowl is 15” and the cut will be an inch and a half inside, we are left with a 12” bowl next.
The second bowl, which will be 12” will have a 10% wall thickness of about one and a quarter inch wide. So, now I will mark the 1.25” on the blank face and make that circle.
The third and final bowl will be about 9 to 9.5” wide. There is no Knife Set for the inside wall thickness of the smallest final bowl. That blank can be mounted to the lathe and turned to final wall thickness using traditional bowl turning techniques.
Depth Measuring Cored Bowls
Just as we measured the diameter of each bowl, now we need to measure how deep each bowl will be when cored.
Unlike measuring the face of the bowl blank, measuring the depth can be a bit trickier.
Since the wall thickness of the largest bowl is one and a half inch, we need to make the depth of that bowl one and a half inch from the bottom of the bowl.
There are a couple ways of measuring the bowl depth. You can stand directly over the bowl exterior and look down on a measuring tape and then lower your pencil to make a mark at the one and a half inch point.
Another way is to use a level and a triangle to determine where the bowl bottom will be. Hold the triangle so that one flat side is facing up and the other flat side is facing outward. The angled side should be closest to the exterior of the bowl.
From the front of the lathe, visualize where the bottom of the bowl will be and use the edge of the triangle to measure one and a half inch inward on the curved bowl surface.
Once you make a mark, rotate the bowl to draw the line all the way around.
The second bowl is one and a quarter inch inside the first bowl. Repeat the process measuring inward an additional 1.25” and make a ring around the outer bowl blank.
Preparing to Core Wooden Bowls
Before we get to that, make sure the Block Clamp is snug up against the lathe bed rails but not tightened yet.
The tool rest and banjo need to be out of the way so, either slide the banjo under the headstock area or remove it completely.
You will also need to have the tailstock ready for added support. A #2 Morse Taper tailstock extensio may be necessary to allow the tailstock to reach across the Oneway Coring System.
Measuring From Center
The method I use to determine the location of the cutting knife requires making measurements from the center point of the rotating knife arm.
Take a permanent black marker and look straight down on the cutting knife while it is mounted in the Base Set. Make a small mark on the knife arm, near the mounting post, at the very center point within the mounting post.
All measurements will be made from the center mark of the knife arm, utilizing this center point.
Positioning the Oneway Easy-Core Coring System
Two positions will determine the exact size and shape of every bowl cored with the Oneway Easy-Core Coring System. The two positions are the distance toward the headstock and the location perpendicular to the lathe bed or rails.
The distance from the headstock will determine the depth of the cored bowl. The distance left of center on the lathe rails will determine the diameter of the bowl.
By far, the more difficult of the two locations to determine is the depth. Let’s start there.
First of all, I core from the center out meaning I core the smallest bowl then the next largest. This method doesn’t require any additional mounting of bowl blanks to continue coring. All cored bowls get cored from the one large initial mounted bowl blank.
Because I core the smallest bowl first, I start with my smallest Knife Set, which is the nine-inch Knife Set.
Visualize the Coring Process
The nine-inch knife has a four and a half inch swing. The center point is critical to understand because that distance will determine the depth of the bowl.
Think of it this way, if we could place the center of the cutting knife flush with the face of the bowl blank and turn the knife, we will have a bowl that is four and a half inches deep.
However, we can not position the center precisely against the bowl face because the knife leg and mounting post are in the way. So for practical purposes, we can not turn a full depth cut with this knife.
That’s fine because we don’t usually need to make cuts that deep in most cases. Instead, let’s look at the line we made on the side of the bowl. Remember those lines?
Doing the Coring Depth Math
If we’re looking at the side of the bowl and we see two lines, we are really looking at the bottom of the two bowls we’re about to core out.
The line closest to the from the rim is the bottom of the smallest bowl. When we made those lines, we made them based on the ideal wall and bottom, bottom thickness.
Now, we need to determine how deep we need to go to get to those marks. Instead of measuring from the bowl bottom, now we measure from the front inward to determine how deep the knife will cut.
Measure from the face of the bowl blank to the first line on the side of the bowl. That measurement is how deep we need to the knife arm to cut.
Remember, the knife arm is set at four and a half inches, but we can position it to make a cut to any depth under four and a half inches.
The depth of the first ring is three inches. Four and a half minus three inches leaves one and a half inches. This means that the center point (the mark we made earlier with the marker) of the knife needs to be one and a half inches from the face of the bowl blank.
With the knife mounted one and a half inches from the face of the bowl blank, it will cut to a depth of three inches.
Adjusting for Bowl Diameter
Adjusting the Oneway Coring System for the bowl diameter is super simple compared to establishing the cutting depth.
To adjust the knife to make the correct bowl diameter, slide the base set toward or away from you until the Cutter tip centers on bowl blank face smallest circle.
Locking the Oneway Coring System
When you move the Base Set one way, the other measurement will need to be rechecked.
The way I position the Base Set is to calculate the depth away from the face of the bowl blank, as we did above, and remember that number.
First I slide the Base Set until the Cutter tip is centered on the bowl blank face pencil circle, the diameter. Then, with a tape measure, I measure the distance from the bowl blank face to the center point of the knife arm, the depth.
When the knife arm is the right distance from the bowl blank, I again check to see that the Cutter tip is on the pencil line. Usually, I’ll need to wiggle it a bit until these two locations are set.
Once the locations are set, I carefully snug up the center bolt on the Base Set which is connected to the Block Clamp underneath. Holding the Base Set with my left hand, I then tighten the Block Clamp bolt with my right hand being careful not to jostle the Base Set.
Position the Supporting Arm
I think Oneway calls the device that supports the cutting knife a “finger.” There’s something about saying “cutting knife” and “finger” that makes me uneasy. (Shrug.) I’m going to call it the “supporting arm.”
With the Knife Set positioned and locked down, the only last adjustment to make is to adjust the supporting arm.
The support arm needs to be centered under the cutting knife at all times.
When you first start cutting, there is no way to position the support arm under the full length of the knife arm. Instead, move the support arm post up to the bowl blank face and center it under the cutting knife.
As your cut progresses, you will need to periodically stop and adjust the supporting arm to provide the most support to the cutting knife.
Note – Be sure you use the correct support arm with the knife being used. Each knife arm has a support arm that matches its curve exactly. If you’re unsure, line up the support arm under the knife to check.
Everything is in place and ready to go at this point. The only thing remaining is to slide up the tailstock and snug it up to the center of the bowl blank.
If the knife arm is in the way initially, this is ok. After the cut advances into the bowl blank, the knife arm will be out of the way, and the tailstock can then be moved into its supportive position.
Oneway Easy-Core Coring System Musts
There are a few things that are very important when coring with the Oneway Easy-Core Coring System:
- The Cutter tip needs to be on the centerline
- Slow is better with lathe speed
- Shavings must be removed from the cutting path
- The support arm must advance and support the knife arm
- The Cutter needs to be sharp at all times
Cutting With the Oneway Easy-Core Coring System
Start the lathe at a slow speed and apply light pressure with the knife arm.
At no point should you need to apply force to the cutting arm to make the coring
You want the shavings and chips to flow out of the cutting path made by the knife. If the chips stop flowing, retract the knife handle to help remove chips.
When the cut progresses deeper into the bowl, you will need to frequently remove the cutting knife from the bowl blank to free up the wood debris.
Moving the Support Arm
When the cutting knife extends a couple inches beyond the support arm post, stop the lathe and adjust the supporting arm.
Loosen the bolt for just the support arm being careful not to move the Base Set location inadvertently.
Move the support arm post to whatever location will allow the support arm to enter the cutting path. Place the support arm near the base of the cut but not all the way to the bottom of the cut, otherwise it may catch when the lathe starts.
As the cut proceeds, stop the lathe, repeat these steps to position the support arm under the cutting knife at all times.
Completing The Core
As the cutting knife reaches more in-depth into the cutting path, you will need to be swinging the arm out frequently to remove shavings.
When the knife handle is almost parallel to the bowl blank face, the cut is almost complete.
Depending on the angle of the cut, the cored bowl may be cut off or may stay held in place. There is no need to turn the bowl any further than when the handle is parallel to the bowl face.
If the cored bowl does not merely come loose, turn the lathe off and see if the bowl can be dislodged by hand.
A bowl that won’t come free by hand may need persuasion with a little prying force. Again, with the lathe off, use the closed end of the Base Set wrench as leverage to pop the bowl free.
If you pry out the bowl blank with a tool for leverage, do so on the side grain side of the bowl. It is easier to chip the bowl blank with the pry tool if it pushes on the end grain side.
Repeating The Coring Process
With the first core removed, now you can move on to the next core.
Remove the handle from the knife set and remove the first knife and its supporting arm.
Insert the next largest knife with its supporting arm and attach the handle to the knife.
We will be essentially repeating all the steps from above.
Measuring Bowl Number Two
Because the measurement portion of this process is a bit challenging to grasp at first, I will walk you through the steps to measure the second cut.
The second line on the outside of the bowl is the depth of the bottom of the second bowl. Measure the straight distance from the face of the bowl blank to this second line.
If the distance is four and a quarter inch, we will need to make the depth of our cut four and a quarter inch. The next knife set is 11.5” which means that it has a 5.75” reach.
We only need to cut down into the bowl 4.25”, so if we subtract 4.25” from 5.75” we are left with 1.5”. This calculation means the center of the knife cutting arm needs to be 1.5” from the face of the bowl blank.
Loosen the base set bolt and move it around until the cutter tip is on the bowl face pencil line and the center point of the knife arm is 1.5” from the face of the bowl.
Oneway Easy-Core Coring System Summary
There you have it. That’s how you core multiple bowls from a single bowl blank using the Oneway Easy-Core Coring System.
Remember the fundamental essentials when coring wooden bowls:
- Go slow
- Remove shavings frequently
- Keep the Cutter sharp
- Always support the cutting knife
Yes, the process of coring bowls takes a little time to set up and understand. But once you comprehend the process, coring bowls is fun, productive, and super efficient.
There is a crazy thrill, for example, of starting with only three bowl blanks and creating 9 or even 12 final bowls. Not to mention the reduced amount of shavings to discard.
If you have not already read my article about sizing and determine what you need to set up the Oneway Easy-Core Coring System, click here and read this article now.
Also, be sure to read this article to understand the Cutter tip sharpening process, because sharpening is an essential part of coring bowls.
We covered a lot in this article. I’m sure you have questions. Please leave comments below, and I’ll do my best to provide answers.
BONUS: There are a couple bonus coring tips here >, check out what I learned from Glenn Lucas in this article.