The bowl tenon, foot, or some call it the spigot of the bowl, is a critical step in the bowl-making process. The bowl tenon must be sized right and cut correctly to make a secure attachment to a four jaw wood chuck during the creation and shaping of the bowl’s interior.
The size of the four-jaw chuck determines the size of the bowl tenon needed. A loose rule of thumb is the tenon should be about 30 to 40 percent of the total bowl diameter.
Bowl tenon size is restricted and dictated by the size of the four-jaw chuck available. Consider purchasing an additional chuck or additional different sized jaws to accommodate a range of tenon sizes.
Larger tenons, of course, will provide more support. Caution needs to be used with small bowl tenons on larger bowls. If you remember you have a tenon that’s a bit small while clearing away the interior of the bowl, this will work with light bowl gouge cuts. I’ve used tenons in the past that were undersized and got too aggressive with my interior clearing cuts and watched as the bowl shot across my shop, snapping off the bowl tenon.
I prefer to make tenons that will later be removed. The look of a nice thin rim that the bowl rests on is more appealing to me. I also like the fact that it makes people wonder how the bowl was attached to the lathe.
Some turners prefer to leave the tenon and let it be the base later. Either way, you decide to finish your tenon is up to you. The creation of the tenon is the same regardless of the final appearance.
Steps to making a perfect bowl tenon
- Make flat area on bowl bottom
- Set dividers to width of four jaw chuck
- Carefully use dividers to mark bowl bottom
- Clear away material up to this mark
- Form inward dovetail angle to match jaw angle
- Make flat shoulder area around tenon
- Test fit four-jaw chuck
If that all seems straightforward, great. There are many nuances along the way that are important and need to be understood well to make the perfect tenon.
How the bowl is attached to the lathe will determine if the base of the bowl is exposed or partially blocked by the tailstock.
Faceplate and screw chuck attachments leave the base open and accessible. Spur Chuck attachments restrict access to the base a bit, because the tailstock must be used to hold the bowl blank.
Start Clean and Flat
While shaping the bowl bottom, create a flat area on the tailstock end that is parallel to the headstock, wide enough for the selected four-jaw chuck plus a bit more width for the tenon shoulder underneath. Push cuts are best for making an excellent flat base.
It’s usually a great idea to remove all the bark, because you want a good solid piece of wood to form the tenon. Also, depending upon the species of timber, the sapwood just under the bark might not be too great for a tenon, either. In this case, continue removing material to get to a solid base for the tenon.
Stop the lathe and lay the bowl gouge shaft across the face of the base. If the surface bows in a concave or convex direction, the flat edge of the tool will indicate.
If you are using the tailstock for support, a nub will protrude in the center of the bowl tenon. This can easily be removed later.
Once an area is cleared flat and wide enough for the tenon, it’s time to mark the exact location of the tenon. With the four-jaw chuck off the lathe, open the jaws a bit. The jaws should create a circle with small openings between jaws.
Expand or contract dividers, preferably shape tipped, to line up across the width of the jaw centers.
Not Too Small
While we want the jaws to be closed down mostly, we don’t want them completely closed. Closing down the jaws completely would leave the possibility of the bowl tenon slipping inside the chuck.
Also, if this is green wood we will be turning it a second time. The tenon will change shape and need to be trued during the second turning and that will remove more material. Leaving the bowl tenon slightly larger accommodates for this down the road.
Also, we don’t want the bowl tenon to be too large, because then the curved inner walls of the jaws are only contacting small points and the bowl could work free easier. The goal is for maximum jaw contact and slight additional area available to tighten the jaws if needed.
With the jaws slightly opened, set the dividers on the center of opposite jaws to set the tenon width and lock it in.
With the dividers set, return to the bowl blank on the lathe. Position the tool rest parallel to the bowl bottom and about an inch away from the surface.
Marking the bowl tenon with sharp dividers, for me, was the scariest part of the process. Lol. The dividers can go flying if you don’t pay attention here.
ONLY the left divider point touches wood. The right side is close to the wood surface but NEVER touches the surface. If it does, it’s going to go flying and hopefully nowhere near you.
The right side is only used to gauge the dividers’ proper position. Rest the left side of the dividers on the tool rest with the dividers approximately centered or straddling the bowl tenon center.
Angle the left divider tip downward to make just a scratch, not a catch and lightly make a mark on the wood. Without moving the dividers look over at the right divider tip and see if the newly created mark is under, or lined up with the right tip. If it’s not, move the left divider and make another light mark until the line is under the right tip.
Be careful not to move the right tip in and touch wood accidentally. Once the spacing is correct, make a deeper mark to indicate the tenon location.
With the tenon marked, use a bowl gouge to begin removing material up to the bowl tenon line. The depth of the tenon needs to be less than the depth of the interior of the four jaw chuck.
The tenon should never touch the inside bottom of the jaws. It is the flat top surface of the jaws that will hold the bowl securely and flat in the chuck, not the interior base. The tenon does not need to be very deep at all. Some turners, especially with smaller bowls, create tenons thinner than an eighth of an inch in depth.
The shoulder area under the bowl tenon needs to also be level and flat. The level shoulder area can be eyeballed by comparing it to the top of the bowl tenon, which is already level.
Now that we have the tenon sized and the shoulder formed, it’s time to make the inward angle for the four-jaw chuck. This step will depend on your particular chuck.
If you have grooved gripping edges and not dovetail jaws, it is still essential to shape the bowl tenon. A smooth-walled cylindrical bowl tenon will work free from the chuck and send a bowl flying—not what we’re trying to do here. Whether you are using a dovetail or serrated grooved jaw chuck, an undercut angle on the tenon is essential.
There are a couple ways to create the undercut tenon angle to accommodate the jaw angle. Let me share with you how I create this undercut angle.
Using a dedicate spindle gouge with a long fingernail grind, I start my cuts on the edge of the tenon and push inward. With the tool rest parallel to the base of the bowl, I place the tip of the spindle gouge at a 90-degree angle right on the edge of the tenon cylinder.
If the gouge is not at a 90-degree angle, it will either be pushed away from the tenon, left or skate across the tenon top, right. Gently apply pressure until the gouge makes a small groove, then slowly add pressure until the spindle gouge is cutting forward. Push the gouge along the edge of the tenon inward making an undercut angle until it meets the shoulder. Repeat this cut until the angle matches the chuck jaws.
If you have a serrated grooved jaw chuck, use the same technique to remove material near the base of the tenon to accept the serrated grooves.
With the lathe stopped you can check the angle by attaching the chuck to the bowl base. If the angle is too shallow, remove more material at the base of the bowl tenon. If the angle is too steep, the area at the top of the tenon needs to be trimmed back, and because of that, the tenon width is reduced.
If the bowl tenon becomes too small and the chuck does not grip, just turn away the existing tenon and create a new one. While this reduces the depth of the bowl a bit, it’s a much safer way to proceed rather than work with an inferior bowl tenon.
Custom Bowl Tenon Tool
After doing many bowls, I eyeball the angle with a spindle gouge, and it matches pretty close. It takes a few bowls to perfect, but anyone can do it.
If you prefer more precision compared to a freehand gouge angle, consider making a custom dovetail bowl tenon scraping tool. Converting a dedicated parting tool into a custom dovetail scraping tool is possible.
Using a simple protractor, measure the angle of the chuck jaws. Grind and undercut the cutting edge on the left side of the parting tooltip. This first ground angle will be used to form the flat shoulder side of the cut.
Now carefully mark the jaw angle on the right side of the parting tool. Make an undercut grind to create this angle.
The parting tooltip now is 90 degrees minus the undercut angle of the dovetail jaw. Once the angle is correct, and the two sides are undercut a bit, not flat or 90 degrees, refine the cutting edge with a finer grit wheel or hand hone the edge for a sharp, clean cut.
Using this custom-created tool is straightforward. However, it is important to realize two sides are cutting or scraping at the same time and this can cause a catch. Want to avoid catches, read this.
Work slow and gently introduce the tip into the tenon bottom corner. If the base shoulder is clean and flat, there should be little or no cutting occurring on the left side of the tool. As the tool reaches the corner it will begin undercutting and making a perfectly matched bowl tenon angle for the dovetail jaws.
If you’d rather not make a custom-ground scraping tool, or you don’t have an extra parting tool to defile, there is an additional option. There are a couple of specialized bowl tenon scraping tools which may be purchased as well.
Hurricane makes a Dovetail Tenon Scraper (check Amazon for current price) which is designed to make a push scraping cut at the perfect dovetail angle. Also, Nova has a Dovetail Chisel that also scrapes a perfectly angled dovetail every time.
There’s one last step before taking the bowl off the lathe and turning it over. We need to mark the center of the bowl.
This step has taken me a very long time to get in the habit of remembering. I think it is because I’m so excited to clear the bowl interior, and I just forget.
Later when the bowl is nearing completion, and the tenon is to be removed or further shaped, it makes it so much easier to mark the bottom center of the bowl tenon.
Making The Mark
The tailstock can be pulled up and, with the lathe turning, lightly push the live tailstock center into the bowl tenon, marking the center.
I like to use the same spindle gouge I use to make the bowl tenon dovetail angle to simply make a little, indented tick mark at the center with the lathe turning. Using the spindle gouge saves the trouble of moving the heavy tailstock for a simple center mark.
That little mark we just made is critical for lining up the tailstock and getting the bowl back to its center to remove the tenon.
Custom Jam Chuck
Using a scrap piece of material, and the same tenon-creating techniques described above, we need to make a jam chuck.
A jam chuck is merely a piece of wood that has been turned round and smooth to match the shape of the interior of a bowl closely. Jam chucks can be made in a variety of shapes and sizes and stored for use with particular bowls.
The nearly completed bowl is then positioned over the jam chuck with the tenon side facing out or right. A piece of foam padding is placed between the jam chuck face and the bowl interior to protect the bowl surface.
With the lathe off, position the padding inside the bowl and center the bowl over the jam chuck. Bring the tailstock up and match the tailstock tip to the center mark created earlier. Apply enough pressure from the tailstock to hold the bowl but not excessive pressure.
Start the lathe slow and confirm the bowl is centered. If the bowl wobbles a great deal, stop the lathe, loosen the tailstock and adjust the bowl until it turns truer. Re-tighten the tailstock and bring the toolrest up to the bowl tenon.
Want more details about making your own custom jam chuck? Be sure to read this thorough article about making jam chucks.
Bowl Tenon removal
Using a freshly sharpened small bowl gouge, make light cuts and gently shape or remove the tenon. Once the bowl tenon area is shaped the way you’d like, reduce the nub connecting to tailstock as much as possible.
Do not try to part or remove this nub with the lathe turning. Instead, make it as small as possible and, with the lathe off, chisel off the nub or sand it off. For detailed information about tenon removal, read Wood Bowl Tenon Removal – 3 Easy Ways.
Bowl Tenon and the final bowl base
As I mentioned before, some people like to leave the tenon as is on the base of the bowl. The bowl tenon can also be turned and shaped into a foot, or it can be removed entirely.
In some cases, notably taller or more angled turned pieces, the tenon and shoulder may be later incorporated and used to increase the final base of the bowl.
After making many bowls, the step of creating the bowl tenon may seem routine and rudimentary.
But the importance of having a proper and secure attachment to the lathe while finishing your bowl cannot be stressed enough.
Learning to make a correct and accurate bowl tenon for a wood turned bowl is a significant step along the path of making great bowls.
If you’d like to know what some bad tenons look like, check out this article.
You might want to see these articles next:
• 5 WORST TENON SHAPE WOOD BOWL (FOOT, SPIGOT, ATTACH)
• WOOD BOWL MORTISE OR TENON – WHICH IS BEST?
• WOOD BOWL TENON REMOVAL – 3 EASY WAYS
Thank you and Happy Turning,