When I first started turning bowls, it seemed pretty straightforward, you take a bowl blank and turn a bowl. Once the bowl was complete, you’re done, right? Maybe, maybe not.
What is twice turning wooden bowls?
Twice turning bowls is a two-step process that reduces bowl blank drying time and assures an even uniform final turning.
First, a thick rough bowl is turned and allowed to dry and contort. Once dry, the distorted rough bowl is turned again making a final bowl that is genuinely round and less likely to further deform over time.
Why twice turn wood bowls?
By removing most of the waste material around the roughed bowl during the first turning, the drying time is significantly reduced.
The main reason to twice turn a wood bowl is to achieve an even round circular finished shape to the bowl, especially around the rim, which is most noticeable.
But, you might be thinking, the bowl “is” round and circular when I’m finished. Yes, when the bowl immediately comes off the lathe, it is relatively round and even.
Over time, however, things are going to change. Wet, green wood moves and distorts as it drys.
Turning Green Wood Bowls Once
When a bowl blank is fresh green wood, the moisture content in the timber can be extreme.
As the bowl is turned, the interior wood is exposed, and the surface area of the bowl, especially the end grain begins to shed moisture quickly.
Typically, the pith ends of the bowl will extend away from each other, and the sides will draw in on themselves.
Depending on the particular tree species and the thickness of the final bowl wall, a bowl can distort to such an extreme it can appear like a football when it drys.
Bowls turned with thicker walls usually don’t distort as severely as thin-walled bowls, but they may have an increased risk of cracking.
Look across the top of a bowl rim, and you may find a subtle wave. This is the result of the bowl continuing to dry and move after being turned.
When To Skip Twice Turning
You can skip twice turning bowls if:
- the wood being turned is already relatively dry
- you desire a more organic natural random appearing final bowl
- the bowl is a natural or live edge bowl (although some people twice turn these too)
- you are creating a thick-walled final bowl
Be aware that the wetter the wood is, the more distortion there will be after the final first turning. That’s
If a particular bowl blank is not very wet but still not completely dry, it will probably move less after the final turning than a very wet green wood.
Twice Turning And Time
Large green wood sized to make a nice bowl blank can hold a lot of water for a very long time.
Solid green wood takes a long time to evenly dry. The rule of thumb is one year of drying time for every inch of thickness.
So, a five-inch deep bowl blank would take about five years to dry completely.
You might be thinking, well that’s ok I’ll stack up some wood and be patient. This is possible, but there is another catch.
Over that theoretical five year period, the outer ends of the log, even if they are well sealed, will probably crack. And inside the log, critters can begin eating and burrowing tunnels all over the blank’s interior.
Twice turning fresh cut green wood not only reduces the drying time, but it also interrupts the crack forming tension and discourages insect destruction.
Twice Turning Green Wood Bowls
So you want to make a perfectly round final wooden bowl? Well, twice turning green wood is the secret trick and, of course, the topic of this article.
The idea of twice turning bowls is simple. Here are the basic steps of twice turning:
- Make a green wood bowl blank.
- Rough turn the bowl blank into an oversized rough bowl.
- Allow the roughed bowl blank to dry.
- Turn the dried rough bowl blank to final bowl shape and thickness.
Those are the simplified steps. Now let’s dig into the details and learn how to twice turn a wooden bowl.
Green Bowl Blank
Typically, the sooner you make bowl blanks from a recently felled tree, the better the blank quality will be.
Cracks, bug holes, and rot can take over a wood supply if it isn’t dealt with promptly.
I use a bandsaw to trim out my bowl blanks before bringing them to the lathe.
Typically, using a faceplate, I secure the blank to the headstock and begin shaping the rough bowl.
Making The Roughed Turned Bowl
The idea of the rough turned bowl is to leave enough material in the walls of the bowl so that when the roughed bowl dries and deforms, it can still be turned true and round while having enough wood to form the final wall thickness.
To determine the ideal wall thickness, we need to know the diameter of the bowl. Use a tape measure and measure the diameter of the bowl blank.
Make the final wall thickness of the rough turned bowl ten percent of the overall bowl diameter. For example, if a bowl is ten inches wide, make the wall thickness one-inch thick throughout the roughed out bowl.
Don’t forget the tenon or mortise. I like to use a tenon, but the general principles apply to a recessed mortise, but in reverse.
Allow at least an extra ten percent on the tenon diameter also. The tenon will stretch into an oval shape after drying, just like the rest of the bowl.
When the bowl is returned to the lathe, we will need to clean up the tenon and make it round again so that it fits perfectly into the four jaw scroll chuck.
If you make a mortise, instead of a tenon, make the original mortise size to just barely fit the chuck. The second trued mortise will be larger once the opening is turned true.
Drying The Roughed Bowl
Many factors including the tree species, moisture content and relative humidity all conspire to determine how long a particular rough turned bowl will take to dry.
If you live in an arid climate, you may need to dramatically retard the drying process to prevent cracks from forming. Or if you are in a humid environment, you may need to use a drying method like a homemade kiln to dry your bowls.
You can always let your roughed bowl air dry and simply wait until it is ready to be twice turned. If you air dry the bowl, keep it away from excessive air movement, heat sources, and sunlight.
I have a full article that goes into great detail explaining how to dry wood bowls, check it out here.
The best way to determine if a roughed bowl is dry or has reached equilibrium is to weigh the bowl. Periodically weigh the roughed bowl with a precise scale, like this digital scale.
When the weight of the bowl stabilizes and doesn’t change much over a week or two, then the bowl is dry and ready for the second turning.
Twice Turning The Final Bowl
You are a patient person. So far, you have turned a rough bowl and waited for it to dry. Your patience will be rewarded.
Using a jam chuck or padded custom reversing disk, mount the roughed bowl to the lathe using the tailstock to hold the tenon end in place.
I used a three-quarter inch thick piece of plywood to make my 15-inch diameter reversing disk. A dedicated faceplate is installed on one side of the plywood disk, and a layer of carpet padding is glued to the work side of the disk.
Take your time and center the main body of the bowl, by using the tenon center, as best as possible. Remember, the wood is distorted, and the roughed blank will not turn true in this deformed state.
With the rough bowl in place, begin making light push cuts with a bowl gouge to re-round the bowl’s tenon. Be sure to not remove too much material and make the tenon too narrow. Stop and measure the tenon diameter as you work.
Once the tenon is true and round again, clean up the tenon shoulder and make sure it is flat and flush with the bowl bottom.
Use your tool of choice to make the inward cut for the dovetail angle on the tenon. I use a push cut with a detail spindle gouge to make this dovetail detail cut. A unique tenon scraping tool can also be used.
At this point, the tenon should be perfectly round with a nice flat shoulder and an inward angled dovetail angle.
Reversing Before Twice Turning
I do not do any further work on the bowl bottom when it is on the reversed jam disk. Instead, I will do all the exterior and interior bowl work while the bowl is mounted by the tenon to the four jaw chuck.
The reason I do both the outside and inside of the bowl while mounted to the tenon is control and precision. Mounting the tenon once assures that the bowl will turn true for the remainder of the turning.
In the past, while I’ve made the final cuts of the bowl exterior when the bowl was mounted in the jam chuck, reversing the bowl never seemed to turn true. The bowl exterior would wobble and be off.
Because the exterior was turned with the bowl on the reversing disk jam chuck position and the interior was turned with the bowl in the tenon chuck-mounted position, the two rotations never seem to match up.
However, when the bowl is mounted once to the tenon, it always turns true because it isn’t being moved to a different orientation that could potentially alter the alignment.
The exterior needs to be worked first before any work can take place in the bowl’s interior.
Because the bowl is distorted, the initial cuts are going to be bumpy. The bowl gouge will be cutting high then low spots, and this can be a bit frustrating at first.
Position the tool rest near the base of the bowl near the tenon connection to the four jaw chuck on the headstock side of the lathe. Make pulling cuts from the bowl base outward.
You can make bevel-supported pull cuts, or you can position the gouge flute towards the bowl surface and make scraping cuts to shape and remove material. See this article about the four bowl gouge cutting techniques, if needed.
Continue cutting until you sense a solid continuous cutting action is occurring. When this happens, it means you have reduced the high sides, and that area is turning round now.
If the pull cut isn’t working well for you, try a scraping cut.
Position the bowl gouge flute facing the bowl surface and keep the tool in line with the center line of the bowl. Scrape with the bottom trailing edge of the bowl gouge and pull the gouge across the surface to even out the high spots.
Use a shear scrape with the bowl gouge to make the exterior of the bowl clean, even and smooth. Here are all the details you’ll want to know about shear scraping with a bowl gouge.
Twice Turned Rim Shape
Shape the rim of the bowl the way you’d like on the outside first and finalize the bowl exterior.
Carefully take your time and form the top of the rim to the shape you’d like. Then determine the inside position or width of the rim.
As the rim takes shape, you will need to determine how thick you want to make the final wall thickness.
Twice Turned Bowl Walls
When the rim is complete, you’re ready to make push cuts with the bowl gouge to shape the bowl interior.
The same high and low areas on the bowl’s outside will be located on the inside of the bowl. Work slowly and level areas from the rim to the bowl bottom, one section at a time.
Take your time and cut the wall thickness evenly across the entire bowl from rim to the bowl bottom. Read this article if you’d like to make the inside bowl bottom perfect.
Stop frequently and check the wall thickness either by pinching with your finger and thumb or by using calipers.
Twice Turned Tenon Removal
With the bowl turned to final thickness and after it is sanded, remove the bowl from the chuck.
Reverse the bowl and return it to a jam chuck position for tenon removal. The same padded reversing jam chuck can also be used to remove the tenon.
Carefully turn off the tenon and shape the foot of the bowl. If you need more details, take a look at this article that goes over all the features of removing a tenon.
Twice Turned Wood Bowl Wrap
When you reach the point of twice turning because you want to make a beautiful, perfectly round bowl, you are a serious wood bowl turner with a vision.
You can see what will be and what can be made from a piece of timber and you are taking the time to respect the properties of the natural material.
I’ve found that the process of twice turning bowls splits up the various tasks of turning and each stage is relatively easy to perform. You do need to be patient and not rush the process.
Waiting for the initial roughed bowls to dry can be a bit of a challenge. However, if you periodically stagger rough turned bowls into your workflow, you might be surprised how quickly dried roughed blanks become available for final turning.
Twice turned bowls might seem like double the amount of work, but the final results can be well worth all the effort.
BONUS: There is a very interesting way to save wood and yield more bowl blanks, check out what I learned from Glenn Lucas in this article.