Intro: Turning a Segmented Bowl
This is my instructable for turning a segmented wooden bowl. I made this one with salvaged wood from old projects and furniture. It uses cherry and maple for the contrast, but you can use almost any hardwoods. I've found that it helps to pick ones of similar hardness. When you sand them, one won't wear down faster than the other. I will be building the bowl blank from segments of cherry and maple glued together. This provides two benefits over turning a bowl from a solid blank. First, there's less waste because the blank will already be hollow, and roughly the dimensions of the final bowl. Second, when turning, you're nearly always cutting with the grain of the wood, rather than across it. (The exception being the disk at the bottom) This reduces tearing, wear on the tools, and makes mounds of those shaving ribbons that are so satisfying to watch fountain off the work-piece and pile up on the floor.
This bowl and more of my woodworking can be seen and purchased at https://adirondackearthlore.etsy.com
(Update: Both of these bowls have sold, but there's still plenty of my other work up there!)
Step 1: What You'll Need
- Plans and a cut list. I generated mine using Woodturner pro, which is available at www.woodturnerpro.com. They have a trial version available so you can play with it and find out if you like it. It's a great program and I've used it for several bowls. (I am in no way affiliated with Woodturner Pro, just a huge fan)
- Dimensional Lumber. Any hardwood should be fine. The amount and length will be dictated by your cut list.
- Glue. A good carpentry glue like Titebond II is recommended. Gorilla Glue works well too, but you have to be careful with your clamping
- Table saw
- Chop saw or miter saw
- Lathe and chisels; I used:
- assorted bowl gouges
- fingernail gouge
- round scraper
- parting tool
- full face shield - Don't even think of starting without one.
- dust mask - a really good idea. The fine dust from sanding some hardwoods are irritants, allergens, and some are just plain toxic.
Step 2: Lay Out Your Plans
As I mentioned, I used the software Woodturner Pro to lay out the basic shape of the bowl and generate my cutlist. The cutlist for this bowl is shown here. It has six "rings" of increasing size, starting with the disk at the bottom. Each ring is composed of 12 segments. For my bowl, I chose to alternate cherry and maple for the contrast.
Step 3: Cut Your Segments; Ring 1 - Disk
I've found that the set up work for making a segmented bowl is far more taxing than the actual turning process. Because of this, I've found it economical to make more than one at a time. It takes time to change from one cutting operation to the next, so I plan on cutting for at least two bowls.
In this case the first ring is a flat disc of maple 4.5" OD (outside diameter) I've marked it with my compass, and I cut it on the band saw.
Step 4: Mount Waste Block and Chuck.
Having cut the disk for the base of the bowl, I now need to attach a waste block so I can screw it onto my lathe chuck. I keep a stack of square waste blocks cut from 2X4's with a hole drilled in the center that will accept an 8d nail snugly to use as a centering tool.
- I used an awl to mark the center of the circle I drew with the compass
- apply glue to the back of the waste block
- use the nail to center the waste block on the disc, and clamp
- let dry overnight.
With those steps complete, I screwed the waste block to my lathe chuck so the assembly can be mounted on the lathe. If you have a 4 jaw bowl chuck, you may want to mount your bowl differently.
Step 5: Begin Cutting Segments; Ripping Ring 2
Following the cut list for ring 2 I ripped boards on the table saw down to the 3" width required. The economy board length listed for this ring is 12 3/4". That means you alternate the orientation of the pieces you will be cutting to minimize the waste. Woodturner pro also provides a "grain match" length which will allow you to make the grain follow around the edge of the bowl, but wastes half the wood.
Again, I'm making two bowls using alternating woods, so I'll cut one board in maple and another in cherry. I also add a little extra to the length measurement because I've found it wise to always plan to cut one or two more segments than I need. Sometimes you will later notice a flaw in a segment (worm hole, crack, etc) that makes it unsuitable for the project. If you find this later in the process, going back and exactly duplicating the size of the piece you need is much more hassle than it's worth.
Step 6: Begin Cutting Segments; Miter Cutting the Segments for Ring 2
Now that my boards are ripped to the specified width, I set the miter on my chop saw for 15 degrees, and clamp a stop block at 1-11/16"; the required segment edge length for ring 2. (the photos above aren't actually ring 2, they're one of the larger rings. I didn't get photos of ring 2 cutting)
Each ring requires 6 cherry and 6 maple, so I'm cutting 1 extra of each color, just in case.La
Step 7: Lather, Rinse, Repeat
The steps for rings 3 through 6 are essentially the same, so I repeat the previous two steps for each ring, ripping to width, and cutting to the specified length on the chop saw.
Step 8: Begin Ring Assembly
Starting with ring 2, Begin assembling the rings.
It helps to dry-fit the ring first. Arrange the pieces in a circle, and if necessary apply your hose clamp around the outside. Check to be sure that all the segments fit snugly. If they don't use a sander to make a minor adjustment to all the segments. Repeat this until they fit snugly.
Apply glue to the segments. I've found that if I apply the glue to the pieces, fit them together, let them sit for a minute, separate them again, and reapply another light coat of glue, I get a better bond. The first coat of glue tends to get absorbed by the end grain of the wood. A second application resolves this problem.
I chose to use my spring clamps to assemble pairs of segments first, rather than trying to get all 12 of them to align perfectly at once. I'm currently not sure if adding the extra step to get better alignment is worth the extra time it requires.
Once the pairs of segments are dry, repeat the dry-fit, sanding, and glue-up process with the 6 pairs, and clamp the ring with the hose clamp.
Once the glue is dry, you can take it out of the clamps, and sand the surface flat. The flatter the better. This needs to glue to the disk with as few voids as possible.
Step 9: Glue Up the Remaining Rings
The process for the remaining rings is the same as the previous step. Repeat until you have all the rings glued up, and surface sanded.
Step 10: Glue Rings Together
Now that the rings are ready, they can be assembled.
Align ring 2 on top of ring 3, taking care to overlap the glue joints on the other ring. If the glue joints align, the final result won't be as strong, and could fly apart on the lathe. Trace the outline of ring 2 on ring 3. This will help show where the glue needs to be applied. It is very important that each ring be centered on the previous ring as accurately as possible, otherwise the blank will wobble on the lathe, and again, it could fly apart.
Apply the glue, fit the ring back in place.
Now apply glue on ring 2 and center ring 2 on it.
I used my drill press as a clamp, advancing the drill chuck down onto the lathe chuck, and locking it in place. alternately, you can simply balance something heavy on the whole assembly, but I've found that difficult. Perhaps in the future I'll make a weight that screws into the lathe chuck.
So far I've only glued together rings 1-3. The reason for this is that I found (the hard way) that my lathe tool rest doesn't reach the bottom of a fully assembled bowl.
Step 11: Mount and Begin Turning
Once the glue is dry, remove the blank from the clamp, and mount the assembly on the lathe. Don't for get to put on your safety gear. A full-face shield is a must. Not kidding. I've watched many sharp chunks of wood bounce off my mask that I would have otherwise worn. So far I've not taken a whole bowl in the face, but many have sailed over my shoulder and made dents in the furnace behind me! This is not a place to skimp if you value your life and vision.
Begin the rough turning as you normally would. Use a large gouge to round off the corners on the outside of the blank. I used a fingernail gouge to define the rough contour of the inside of the bowl. continue smoothing the contour, working to smooth out the curve of the surface so that it just touches the joints between the rings, and removes all the flat spots from the rings.
Once the basic profile has taken shape, and there are no flat spots visible, switch to a scraper taking light cuts to continue smoothing the surface. Keeping the tools sharp will reduce the tear-out between the segments. I found that I always had a bit of tear out on the trailing edge of some segments. Don't worry, aggressive sanding will take care of that.
Take care not to round over the top edges of the bowl yet, there are still two more rings to add.
Do some coarse sanding with 60 grit paper; just enough to remove any digs left from tear-out.
Use the scraper to flatten and true up the top edge of the bowl a large, flat sanding block with coarse paper will help true the edge to receive the next ring.
Step 12: Glue Remaining Rings; Complete Turning
Now the remaining rings can be centered and glued in place.
Once the glue is dry, the remaining rings can be turned and the final profile can be refined with scrapers and coarse sanding.
Another Safety warning:
Don't forget your dust mask during sanding operations. Some woods are irritating or toxic. Spalted wood can contain spores that may be distributed during sanding. Getting them in your lungs can actually cause a fungal infection in your lungs.
In the photo above, I was trying to get a jump on the work because I didn't have enough hose clamps to glue all the rings at once. I turned rings 1-4 while 5 was gluing, and I turned ring 5 while 6 was still gluing up.
Step 13: More Sanding and Finishing
Sand the bowl with increasingly fine grits until you've reached the surface you want. I worked up from 60 grit through 100, 200, 400 sandpaper, and 0000 steel wool.
When you think the sanding is complete, inspect the bowl CAREFULLY for small dings and tear out. The're hard to spot when the bowl is unfinished, but they become painfully obvious once you have two coats of finish on (again, learned this one the hard way).
Since this bowl could be used for food, I used a food-safe tung oil finish. Rotate the bowl by hand as you apply the tung oil with a cloth or brush. The first coat can be fairly heavy, as the wood will absorb it quite quickly. You can apply a second coat within an hour. After the second coat, follow the instructions on the can for your finish. I waited 8 hours for the tung oil to dry and harden, and then I sanded again with 400 grit, and applied another coat. Repeat as necessary, using increasingly fine grits
Finally, I buffed the finish with a brown paper bag, followed by a cotton rag. This provides a very glossy finish.
Step 14: Part It Off
With the parting tool, separate the bowl from the waste block. This step is much easier if you have a partner with their hands ready to grab the bowl when parts off. You'll see it start to wobble a bit right before it separates.
Alternately, if you can't find someone to help, part it down to about an inch, stop the lathe, and cut off the rest with a coping saw or hacksaw.
Turn the bowl upside down onto a soft cloth. With a chisel, carefully shave off the button on the bottom.
Sand and finish the bottom of the bowl.
Step 15: All Done. Lessons Learned
That's it, your bowl is done.
Here's what I learned:
When the bottom of the bowl is hollowed out, a circle of the bottom disk shows through ring 2. Since the wood of ring 2 is very thin at that transition point, the circle is not perfectly round. It's not extremely noticeable, but it could be better. When I did the second one, I turned a 3/4" peg from cherry, and drilled a 3/4" hole in the center using a forstner bit mounted in my tail-stock. This hole went all the way through ring 2, and halfway into the disk of ring 1. I glued the peg into it so that it stuck out a bit, then turned it flush with a scraper. This made the circle at the center of the bowl much sharper and well defined.
I need more hose clamps. The process would have gone much faster if I had enough hose clamps to glue all the rings at once. As it was, I could do two smaller rings at once, but only do one large ring at a time. It would have gone much faster if I had enough clamps to do all the rings at once.
My turning tools never seem to be sharp enough. I don't have any sharpening jigs for my chisels, so I sharpen by hand. I'm still getting the hang of this, so it takes longer than I'd like to get a consistent edge. As a result, I don't do it as often as I really need to.