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AW Extra 4/4/13 - Turning a Green Wood Bowl

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Turning a Green Wood Bowl

By Alan Lacer


Making a functional object directly from raw material in its natural state is incredibly satisfying. Just ask any potter. For woodworkers, green woodturning captures that feeling. You literally start with a log and end up with a beautiful bowl.  If you’ve never turned green wood before, you’re in for a treat. Green wood is easier to turn than kiln-dried wood. It cuts cleaner and produces very little dust. To top it off, the wood itself often costs nothing. 

 

Tools and supplies:

1/2” bowl gouge 

(from a 5/8” rod)

1-1/4 to 1 -1/2-in. 

heavy scraper  

(usually 3/8” thick)

Jacobs style chuck 

A 5/8” to 1” drill bit

Double ended calipers

Vernier style caliper

Sanding discs and soft pads (5” and 2” dia.)

Flexible shaft tool or flexible shaft for a drill

1/8” rubber router mat material

CA glue

 

Material

The process works best if the wood is wet and freshly cut. Storm-downed trees, areas being cleared for development and tree service dumping sites (often called “bone yards”) are all good sources of green wood.  For ease of handling and cutting, choose logs or limbs that are smaller in diameter than your lathe’s swing.

Almost any species is worth trying, but here are some of my favorites: maple, walnut, butternut, ash, birch, locust, white oak, cherry, beech, Osage orange, and pear. My rule for green bowls is to try whatever is locally available—you may be pleasantly surprised by the abundance of material in your own backyard.   


Safety first!

Wet logs weigh a lot! You don’t want one flying off the lathe. Use a faceplate that’s made from one piece of steel and is at least 3/8” thick at the screw hole flange. For bowls less than 10 inches in diameter, I use a 6-hole, 3-in.-diameter faceplate. The type of screw is also critical: Use #12 sheet metal screws. Avoid dry wall, deck and wood screws. Be sure the faceplate sits flat on the log’s surface—if it doesn’t, use a small hand plane across the grain to create the desired fit. Last but not least, be sure to wear a full-face shield—goggles are not sufficient for bowl turning. 

 

Finishes

Is your bowl functional (made for food) or decorative?  If it’s decorative, choose any finish that gives the look and feel you prefer. My favorite finishes for functional bowls are mineral oil, walnut oil and pure tung oil. Mineral oil looks great on light colored wood, as it adds no color of its own. However, it never dries so it needs to be reapplied regularly, especially after washing. Walnut oil adds a little color and will dry in time. It’s available at health food stores.  I also like pure tung oil. It adds a deeper color that looks great on dark woods and it will dry. 

 

Tip: Avoid a splintered rim

If you run the tool off the ends of the blank into air (most commonly at the rim area), the fibers will break off along the edge—much like sawing through a board that is not supported on the back side of the cut.

Solution:  Work from the open air into the wood for the first 1-in. or so. (see Photo 11)

 

Tip: Prevent drying cracks

Every green bowl will distort as it dries—I think this adds character. Too often green-turned bowls dry so rapidly they crack. Slow down the drying process by placing the completed bowl in a two paper bags. Store it in a cool damp location. 


1. Cut green bowl blanks in lengths that are equal to the log’s diameter, plus one inch. Start by lopping off a short section to eliminate any end checks. Mark a line through the pith where the log will be split into two bowl blanks.

Click any image to view a larger version.




2. Cut the log along the marked line. A 1/2” wide, 3 to 4 tpi skip tooth blade is a good choice for a 14” bandsaw with riser blocks. If the log is too big to cut on your bandsaw, use your chainsaw or split the log with a wedge.



3. Round up the blank using a 1/4-in. plywood template as a guide. I keep a set of these discs in 1/2-in. increments. Simply nail the template on the bark edge and follow the shape.



4. Locate the faceplate on the blank’s flat surface. This will eventually be the inside of the bowl. Center the round template on the blank and use the nail hole to mark the center. Then draw a circle that’s slightly larger than the faceplate’s diameter.



5. Screw the faceplate into what will be the opening of the bowl. The screws should penetrate the wood at least 1” for initial rough turning.



6. Rough the bowl with a bowl gouge. Point the  flute in the direction of the cut and keep the bevel rubbing on the wood. The tailstock adds support.



7. Remove the tailstock and flatten the bowl’s bottom  with a scraper. The bottom must be at least  1-in. larger than the faceplate.



8. Draw a series of circles with a pencil to aid in mounting the faceplate for the next step. One of the circles will be close enough to the size of your faceplate to center it. Remove the bowl and remount the faceplate on the base.



9. The bowl is now mounted with the base towards the headstock. Cut the bowl’s height so the pith is removed. Use the gouge in a scraping fashion with the bevel facing away from the wood and the bottom edge scraping.



10. Begin the final shaping.  Establish a base with enough waste for the screws. Then, concentrate on perfecting the upper two-thirds of the bowl. Work from small to  large diameters to reduce tearout.



11.  Finish with a shear-cut. Place the gouge high on the piece and keep the bevel rubbing. You can tell a good shear cut by the thin, wispy curls of wood. Work up to within an inch of the rim, then from air into the rim (see TIP).



12. Start the hollowing process by drilling out the center of the bowl. The hole gives a place for the tool to end each cut and eliminates the need to constantly check the depth. Use a 5/8—1-in.-dia. bit mounted in a Jacobs-style chuck.  Drill to a depth that is 1/2-in. less than the finished depth will be.



13. Hollow the bowl’s interior. Start an inch or so back from the drilled hole.  Roll the tool on its side to about a 45-degree angle and cut with the bevel rubbing. Work from large to small diameters. Continue this backing-up process until the walls are 3/8 to 1/2-in. thick.



14. Shape the rim with a scraper before you finish hollowing. Green bowls change shape rapidly once they are hollowed, making the rim nearly impossible to shape later. Here, I’m rolling the rim to round it like a bead.



15. Establish the bowl’s final depth with a heavy scraper. Use the scraper for the bottom and a little up the sides. Scrapers cut poorly across end grain, so rely on the gouge for cutting most of the bowl’s sides.



16. Remove the extra material around the faceplate and base of the bowl. Then, remove the bowl from the lathe—but don’t unscrew the faceplate just yet.



17. Reverse chucking is a way to mount the bowl backwards in order to finish off the underside of the base. Start by mounting a dead center in the headstock. Then screw the bowl back on the lathe so the pin marks the center of the base. Remove the bowl from the lathe and unscrew the faceplate.



18. Mount a 2-in. thick block of wood to your faceplate. True the sides and flatten the face.  Slightly round the corners where the sides meet the face.



19. Glue a piece of router anti-slip pad to the chuck.  I use CA glue on the wood and an accelerator on the rubber for an instant bond. The inside of the bowl will be held against the rubber with pressure from the  tailstock.



20. Use calipers to mark the depth of the hollow on the outside of the bowl. It’s good to know where the bottom of the bowl is as you cut the base. Set the bowl over the chuck and bring the tailstock forward to engage the center mark you made earlier on the base.



21. Cut away the waste block where the screws were fastened. Refine the final shape of the base and the bottom third of the bowl with light, finishing cuts.



22. Undercut the bowl’s base to create a rim for the bowl to sit on. This looks better than a flat bottom. Watch the bottom mark (made by holding a pencil on the mark made earlier) so you don’t cut too deep.



23. Break off the remaining nib with a rap from a tool handle. It takes little effort to break the nib. This leaves a small area to be cleaned up by hand.



24. Sand the bowl after it has dried for 4-5 days. Use a soft foam-backed disc mounted on the lathe with a drill chuck. Keep the bowl moving to avoid creating flat spots. Start with 100- grit and work through 220 - grit.



25. Sand the inside with a smaller foam disc.  A flexible shaft that attaches to your drill or a flexible shaft tool such as a Foredom works well for getting  inside the bowl.




This story originally appeared in American Woodworker September 2007, issue #130.

September 2007, issue #130

Purchase this back issue.