The purpose of this tutorial is to show that your imagination and a little knowledge can go a long ways when you are designing turned items on the Legacy Ornamental Mill. Many items produced on the mill tend to be symmetrical designs limited to a single router bit. In the world of woodturning hand produced items appear to have many more options than what our equipment is capable of. It's my intentions to show that this is not the case.
You can create quite a few traditional hand turned features using standard router bits. Most spindle designs are based on simple shapes such as beads, coves, straight or curved lines. It's the combination of these shapes that creates designs. I define "Complex Profiles" as the combination of multiple shapes to create a new shape. Most router bit companies sell the bits to produce those basic shapes seen in woodturning. Legacy Woodworking worked with Magnate to create router bits that combine the basic shapes to make it easier to duplicate the complex profiles found in traditional woodturning.
One of those complex designs is the bead, fillet and cove combination. This profile is known as the "Classic Plunge" in Legacy 's world. It's a "classic" in that the fact that the radius of the cove matches the radius of the bead and a straight line connects them. This is a mathematically correct form that is known to please philosophical turners world wide. Here's what they look like.
Back in the real world we often find in hand turning you will not see this precise of a form executed very often. You will often see round beads and a more shallow curve in the cove connected with a straight line also known as a fillet. Here's an example of a more subtle design following the same pattern. The question is how would you make this?
To create this profile, a custom bit could be made as shown on the illustration on the right. There are times where a stock router bit profile might come close. However, why settle when you can gain flexibility by building the profile with common bits that you have access to. Referring to the diagram above and right, we can see a bead shape labeled "A" that is clearly a simple radius. Curve "B" looks a little more complicated and appears to be an ellipse. In fact it's really just a circle where only a portion is used. Line "C" is our straight line (the fillet) that connects the two.
Here's a another way to look at our desired profile. The dotted lines complete the circles and make it clear that these can be made with a core box bit, a straight bit and a round over bit to form a more elegant profile.
As long as the diameter of "B" does not run into the diameter of "A", we can create the profile as shown. The bit selection can even be simplified to just two bits, a "Core Box" and a "Plunge Flat Roundover" as will be shown below. Using these basic principles, many profiles can be made.
To cut the complex profile, you would start by locking the carriage in place on the X-axis and determine the depth of your cove. A core box bit is used to make this cut.
Next you would cut the bead on the left or right side of the cove using the plunge flat roundover bit. Notice that the selection of that style of bit is a complex router bit since it combines a radius and a flat line. The width of the fillet would be variable and not restricted by the width of a straight cutting bit that would normally cut both sides at the same time. When cutting the bead, you should be aware of proper cutting direction to prevent tearout. The carriage should be locked on the X-axis to prevent movement.
You might notice that this profile could be an attractive design. If you stopped now, you would have a non-symmetrical design that is often seen in hand turned items. This works great for transitions between two shapes.
To complete our original design, we simply need to move the router to the right side of our work and rotate the spindle the opposite direction to prevent tear out and cut the right side bead.
That's all there is to creating custom complex profiles on the Legacy Ornamental Mill. Keep in mind that the same techniques can be used on flat molding and on multi-sided turnings.
I hope you are now more aware of seeing your designs in a new way. You are not limited by the set of router bits that are currently made. Thinking in basic circles and lines, many shapes can be dissected and cut using off the shelf router bits. This is really important if you are going for a unique look in your turnings that simulate hand turned items or when you find yourself replicating antique items.
The machining of these complex profiles is beyond the
scope of this article. It's a topic that deserves
an article by itself due to the many options that have been developed since
the manual machines has been released.
For starters, the method shown above could be "Winged" by using your eye to align the coves and beads. Making your fillet wider would not destroy the design the same as a deeper cove would not effect the over all design. You could also start out with a very specific design using either a cad drawing or the design kit to provide you with real numbers to locate your router bits. The choice is up to you.
There is also a great tutorial on the design kit on Legacy's Site.
Any question or comments, feel free to contact me
Web Page added 6-1-2011. First Draft