Bowl tenon removal is one of the last steps to finishing a wood bowl. After a properly formed tenon has done its job, its no longer needed and must to be removed from the soon-to-be-finished bowl.
Depending on the final bowl foot design, some of the tenon areas may become incorporated in the bowl base. The amount of available material near the base of the bowl will also determine how much of the tenon stays or goes.
Typically, the jaws of the four jaw chuck will mark up the sides of a tenon, making it noticeable if the tenon is left intact. Cleaning up the side of the tenon should be considered at a minimum, even if you don’t plan on removing the full tenon.
Here are three easy bowl tenon removal methods to consider when finishing your bowls.
Three Bowl Tenon Removal Methods
1) Jam Chuck
The jam-chuck bowl tenon removal method is the easiest but does not allow full access to the bowl bottom while on the lathe. The jam-chuck tenon removal method is also the cheapest route because no additional accessories are needed.
If you’re turning a bowl without a chuck, a jam chuck can even be created without a four jaw chuck if desired. Mount a scrap block or cylinder of wood to a faceplate and mount it to the lathe.
If you already have a waste block with a tenon, re-attach the block to the four jaw chuck and smooth the outside face and sides. I also like to make a rounded edge along the front edge to prevent any marks on the inside of the mounted bowl.
Making a Jam
If you don’t have a previous waste block, then you will need to form a custom jam chuck from scrap timber. Start by turning a piece of wood into a short cylinder that is approximately half the diameter of the bowl interior.
The new jam chuck can be turned end to end with a tenon shaped on one end to fit in the four jaw chuck. Another option is to use a dedicated faceplate and attach the wood to the lathe with a faceplate first then shape the wood into a cylinder. The faceplate method does not require the use of a four jaw chuck.
I prefer to make jam chucks with tenons because they are so much easier to reuse and change out with a four jaw chuck. This technique also makes it easy to have several different sized jam chucks at the ready for various sized and shaped bowls.
These are the basic steps for making a jam chuck. For a more detailed explanation of making jam chucks, check out this article next.
Jamming the Bowl
Here are the steps to mounting the bowl to the lathe for tenon removal using a jam chuck.
- Mount the shaped jam-chuck on the lathe.
- Prepare the tailstock with a live center quill.
- Position the banjo about midway on the lathe bed rails.
- Place a piece of scrap foam or carpet padding between the jam chuck face and the bowl interior.
- Hold the bowl firmly against the jam chuck.
- Slide the tailstock up to the bowl bottom.
- Lock the tailstock and move the quill forward.
- Match the quill tip to the small center indent made while creating the tenon.
- Tighten the tailstock on the bowl.
- Rotate the bowl by hand while marking any high spots near the too rest.
- Loosen the tailstock a bit and shift the bowl to make it more centered.
- Tighten the tailstock.
- Turn the lathe on low and make a pencil tick on the tenon.
- If the mark goes all the way around the bowl is centered.
- If the pencil only marks a particular area of the tenon, stop the lathe and move the center of the pencil line area slightly inward towards the quill.
- Remark the tenon with the pencil and adjust until the bowl is centered.
It is time to begin the process of bowl tenon removal once the bowl is centered as best as possible in the jam chuck.
Making the Cuts
Position the banjo under the tenon and make the tool rest parallel to the tenon base. The right end of the tool rest should be very close to the tailstock live center quill. Lower the rest just a bit so the bowl gouge cutting tip will be on center.
I had an experience during a bowl tenon removal once when I had the tool rest a little below center, and the tailstock wasn’t tight enough. My bowl gouge simultaneously became a pry bar and a ramp. The gouge, being too low, pried and popped the tenon off the lathe. With the bowl’s forward rotation, the bowl shot right up my tool and bounced off my face shield.
Thank goodness for that face shield. I took quite a punch, but nothing was cut or broken. Now I’m super careful to center the cutting tool and tighten the tailstock on every bowl I make. It was a good lesson learned…the hard way! Ha.
Wear your safety gear! Here is my recommended safety equipment guide.
Shaping the Base
If you haven’t already decided, now is the time to determine what kind of bowl base you’re creating. Be careful not to remove too much tenon material, leave enough to shape the desired base.
Many times I leave a gentle outside curve leading to the base rim. Usually, I’ll clean this up a bit and then match the interior of the bowl base with a similar inward concave path to the bowl center.
I like first to square up the bottom edge of the base using my 1/2” bowl gouge. With the bottom edge clean and square its easier to see exactly what will be removed and from where.
With the outside of the bowl base already shaped and the bowl base bottom square, I then make scooping push cuts to remove the center area. I try to make light cuts and work slowly.
It is important to know there is enough bowl thickness to be working with at the bowl base. Unfortunately, with the bowl mounted in a jam chuck and centered, it is a troublesome process to unmount the bowl, measure the thickness of the base, and then remount the bowl.
Measuring the bowl beforehand can be done, but it’s difficult to calculate what will remain after working the majority of the tenon. I typically match the bowl base to the side walls and try not to make the center bowl base protrude deeper than the surrounding area.
I’d like to say that will work every time but to be honest, I have made a couple of bowl bottoms very very thin, like transparent thin. 🙂
If the interior bowl shape is a fluid curve then the outside walls will also have a fluid curve, which continues through the bowl bottom. Like so much in wood bowl turning this too will become second nature with a little practice.
Bowl Tenon Removal Cone
A connecting cylindrical shaft remains from the live tailstock center to the bowl while trimming and forming the bowl base. With the bowl base nearly complete, it’s time to focus on this cylinder.
With small nibbles, work from top to bottom reducing the cylinder until it begins to look like a cone pointing into the bowl.
It’s a good idea to stop the lathe and inspect the cylinder/cone for any defects. If the wood in this area has any cracks, bark enclosure, or anything that makes it look insecure, stop turning now. Remove the bowl and chisel or sand away the remaining wood center stub.
If the cylinder or cone shaped area looks like solid wood with no voids or cracks, continue trimming the cylinder down to a small cone. Do not cut through the cone with the lathe turning. Simply, get the portion of wood that remains on the tenon cylinder down to the smallest size without detaching the bowl.
With the lathe off and the cone as small as possible, there are a couple of ways to remove the remaining nub of the bowl. Use a small Japanese pull saw to cut through the cone base if the cone will not break off by hand. A pull saw is an excellent tool for so many tasks in the shop.
Once the cone is off the bowl bottom, a small nub will remain. A sharp chisel can be carefully used to remove the remaining core and level the bowl bottom. Also, sanding will usually accomplish the same task.
For a complete guide on sanding, read Bowl Sand Tools and Finish Techniques.
Using my power sanding drill and foam sanding pad, I usually sand off the remains nub. A sanding disk at 120 or 180 grit sandpaper or sanding mesh works well. I’ll then finish the area with 220 and 320 grit before applying a finish. Here are is my recommended sanding equipment guide.
2) Rim Mounted Bowl Tenon Removal Method
Special chuck jaws are available for reverse mounting a bowl rim which leaves the bowl tenon area open and accessible for easy turning. Large work jaws are designed to easily attach to the four jaw chuck I recommend using.
With the large work jaws mounted to the four jaw chuck, the rubber supporting nubs need to be positioned to suit the particular bowl size being turned. There are numerous holes for adjusting and accommodating almost any size of bowl within the jaws’ range.
Initially, it is good practice to pull up the tailstock for support and to confirm everything is smooth and balanced. Once the wood chuck and jaws stability is confirmed, the tailstock can move out of the way.
With the bowl is secure, position the tool rest and remove the tenon and shape the bowl base. It really is that simple.
The only downside to these large work holding jaws is they don’t hold irregularly shaped bowls very well. As I turn many natural edge bowls, I don’t use this technique in my turning process. However, if you make bowls with even rims, this can be an excellent solution.
3) Vacuum Chuck Bowl Tenon Removal
The vacuum-chuck bowl tenon removal method is like a magic trick that I never get tired of using. When I first heard of this, I thought there is no way that could work. Well, it does work and very well.
Before I purchased my Hold Fast 3″ Vacuum Chuck Kit 1-1/4″ x 8 TPI (also available with 1” x 8 connection) I was very curious as to how this contraption would work. It turns out to be super simple and very efficient.
The only thing needed, besides the vacuum chuck kit is an air compressor. I use a small Porter Cable Air Compressor (check Amazon for the current price), and this air compressor is more than enough to maintain vacuum as I turn.
A hollow threaded shaft fits through the headstock and is tightened on with a rubber sealed nut at the headstock. At the rear of the headstock, a bearing connects to a small hose, and the hose runs to a regulator. That regulator has a connection for the airline from the air compressor. That’s about all there is to it.
Once the airline is in place, the plastic and rubber seal lined chuck screws onto the headstock threads, and the system is ready to use. Place a bowl up to the chuck, turn the compressor valve switch on the regulator and “voila” the bowl holds in place like magic!
The tailstock can be used to line up the bowl bottom using the small center tick created when the tenon was first shaped. With the bowl centered and the vacuum holding the bowl, remove the tailstock and begin turning.
You will want to make light cuts and watch the regulator gauge occasionally as you turn to maintain proper vacuum.
Remove the tenon and form the base as you’d like, free of any obstructions. Hold the bowl when it is complete and turn off the regulator and the bowl drops to your hand.
This system worked so well that I went back and purchased the 6” Vacuum Head 1-1/4″ x 8 TPI which lets me vacuum attach larger bowls now.
The company that makes this vacuum chuck also makes an ingenious tool to help center the bowl correctly on the vacuum chuck. The Hold Fast Chuck Reversing Adapter 1-1/4″ x 8 TPI – MT2 (and 1” x 8 version) is a device that allows the entire chuck and bowl to be removed from the headstock once the bowl interior is complete. The reversing adapter slides into the hollow tailstock center and then the four jaw chuck, with bowl attached, is threaded onto the reversing adapter.
When the vacuum chuck is installed on the lathe using this reversing adapter, the tailstock, now holding the bowl, can be slid towards the headstock until the bowl touches the vacuum chuck.
Because the tailstock is centered with the headstock, the bowl if perfectly centered on the vacuum chuck. Vacuum is applied, and the bowl can then release from the four jaw chuck. The reversing adapter and tailstock can be moved out of the way. Its a super simple and perfect way to center the bowl every time.
Whether you decide to use the jam chucking, large work holding jaws, or the vacuum-bowl tenon removal method, tenon removal is not all that difficult.
Bowl tenon removal is relatively straightforward but can make the difference between a good bowl and a truly elegant piece of woodturning. Take your time with removing the tenon and forming the base, and the results will speak for themselves.
Let me know if you use one of these bowl tenon removal methods or if you have another way to finish the base of your bowls. Please leave a comment below.