Thursday, April 3, 2008

Bruce Perry Demo - March 2008

Winged Bowls

Presented by: Bruce Perry

Reported by: John I. Giem

On March 6, 2008, Bruce Perry presented his method of turning a ‘winged bowl’ to the Loveland Woodturning club. He got started on doing this kind of turning after getting ‘bored’ from turning many bowls. He is trying to make a turning that resembles a teapot setting on a leaf of a flower.

Bruce Perry, winged bowl-2.jpg

Bruce Perry, winged bowl-2.jpg

One of Bruce’s winged bowls.

For the demo, Bruce used a piece of rectangular spalted birch about six inches by ten inches. He mounted off-center toward one corner between centers on the lathe. At the headstock, he used a disk covered with sandpaper mounted in a chuck. A live cup center without a center pin was used in the tailstock. He believes that a screw center has too high of a risk toward coming loose.

For safety reasons, the audience was split to two sides leaving a clearance in line with the piece being turned. During the demo, Bruce only wore safety goggles because his normal full face shield would interfere with our being able to hear him.

- The turning speed is critical. The faster it turns, the easier to cut and get a smooth finish. If it is turning at the resonance speed then the lathe will vibrate heavily and move all over the place. The turning speed MUST be either below or above the resonance.

- The initial cut was an arcing cut from inside to outside.

- He often uses a bandsaw to remove part of the waste after the initial shaping.

- The tailstock will eventually get in the way preventing the rubbing of the bevel on the gouge. At this point he switched to a bowl gouge with a straight across grind. This allows the continuation of bevel rubbing resulting in better control and smoother cuts.

- A tenon was turned on the bottom of the piece (that side toward the tailstock). He wants just enough to mount in the chuck be strong enough to hold but not so much that it interferes with the design.

- Uses a skew as a negative rake scraper to help smooth the surfaces.

- When he reverse mounted the piece using the tenon and chuck, he also used the tailstock to help stabilize the work.

- Keep the tool rest close to the work to give good support to the turning tools but yet far enough away so that the tool is supported on the shaft not its’ bevel.

- Cut from the outside toward the center leaving the thicker sections toward the center. If one were to cut from the center outward, then the thinner inner sections would work like a hinge allowing the outer rim to flex and vibrate.

- For better control, keep the tool rest parallel to the path of the cut.

- He turns the outer edge to about ¼ inch thick.

- When the cutting of the wing approaches the base of the pot or bowl, the clearances get tight and
there is the risk of catching the wing of the gouge and causing a ‘dig in’. To avoid this, he
switches to a spindle gouge and specially shaped scrapers.

- When possible, use heavier (thicker) tools to minimize unwanted vibrations.

- The scraper he uses to carve out the base near the bowl is a specially ground hooked negative rake scraper. Since this scraper gets relatively little usage, he ground it from an inexpensive carbon steel skew.

- He finds that the wings of the piece look better if they are just a little thicker at the outer end and a little thinner on the curve going back to the pot.

- He drilled a depth hole in the center of the pot (vessel) using a spindle gouge.

- Small hollowing tools with a negative rake were used to hollow the small vessel.

- He remounted the piece with the vessel mounted on a jam chuck. The chuck was custom turned to fit on the outside ‘downhill’ side of the bowl. There was a ¼” hole drilled through the chuck so that if the piece got stuck on the chuck, it could be removed using compressed air through the hole. The tailstock was used to hold the piece firmly on the jam chuck.

- The wings are sanded without the lathe rotating by using a two inch random orbit sander. The tool rest is removed while sanding to provide more room and access.

- He will use about three applications of sanding sealer before starting to sand.

- The sanding sealer will help stabilize the softer portions of the spalted birch. These softer sections are difficult to get smooth with the turning tools due to their softness. The sealer will improve their durability.

- Bruce took the piece home with him where he will finish the finial turning, sanding and finishing. He will bring it to the Symposium in September and enter it for auction to support the education grants.

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