Robert Anderson: Turning Inside-out Ornaments

These ornaments are turned in stages. The blank is assembled from four identically dimensioned sticks to form a block. The exterior of the block is then turned to a deep cove. The block is then disassembled, the four sectors each turned 180° and reassembled and glued with the turned surface forming the interior. The new exterior of the block is then turned to form the hollow body. The ornament is completed by adding top and bottom finials.

Preparing the Blank

Blank preparation is critical in this project. Each of the four sectors that will form the blank must be perfectly square and identical in dimension. Robert made his sectors 1¼" × 1¼" × 4½". He used a series of passes through a band saw and thickness planer to ensure uniformity of the dimensions. The four sectors were assembled into a 2½" × 2½" × 4½"; inch block and held together with wraps of masking tape around each end. Staples were used in the end grain to secure the sector joints. Each sector was marked on the end with a number so the orientation could be maintained later. This preparation work was all done in advance of the demonstration. Maple and walnut are good woods for this project. Dense, fine grained woods are preferred.

First Stage Turning

The assembled blank was mounted on the lathe with a four-jaw chuck and live tail center. Care must be taken to ensure the blank is precisely centered before cinching down on the chuck. At a lathe speed of about 1500 rpm Robert used a ½" bowl gouge to turn a deep symmetrical cove cut centered on the length of the blank. The bowl gouge provides more rigidity than a spindle gouge. The finished cove ended about ¾" from each end of the blank and with about 1¼ inch of diameter remaining at the bottom of the cove. Going any deeper would make the sections too thin when reversed leading to too much vibration in the stage two turning. This cove cut was sanded through 400 grit. The piece was then removed from the lathe and would be disassembled by removing the staples and the tape. Each sector piece would then be rotated by 180 degrees and carefully reassembled in the same order as before. The result will be a square block with a hollowed interior. This assembly would be glued with Titebond and clamped. It is wise to let this glue-up set for three days before additional turning to prevent a joint failure.

Second Stage Turning

The glued block is remounted in the four-jaw chuck with a live tail center as before being careful to ensure exact centering. Robert again used a lathe speed of about 1500 rpm and began turning the exterior of the block with a ½" spindle gouge. He rounded the tail-stock shoulder of the block and cut a dove-tail spigot on that end for rechucking. He also faced off the end of the block to dead flat in preparation for drilling. The live center was removed and a Jacob's chuck installed in the tailstock. With a 3/16 inch bit drill a hole completely through the end of the piece into the hollowed center.

Remove the piece from the lathe and remount with the dovetail spigot in the four-jaw chuck again using care to center the free end on a live center in the tailstock. Round of the shoulder on the tailstock end of the block as before and face off the end as before. Using the Jacob's chuck in the tailstock, drill a 3/16 inch hole through the end of the piece as before. Remove the piece from the lathe.

To finish turning the exterior of the piece Robert replaced both the chuck and the live center with home-made friction drive mandrels. Both were wood blocks that had been bored and tapped to thread onto the spindle and a tailstock adapter respectively. Robert did the initial boring and tapping then soaked the threads with thin C/A glue and re-tapped them to provide a smooth, hardened thread. He then turned the blocks into a rounded cone shape and glued 3/16 inch diameter pins into the tips of each cone.

The two friction drive mandrels were mounted on spindle and tailstock respectively and the partially turned ornament was mounted between them with the pins engaged in the holes previously drilled in both ends of the ornament. Robert suggested that a little powdered rosin on the pins greatly improves their grip on the piece and minimizes spinning on the mandrels. The exterior profile of the ornament was then refined with the spindle gouge establishing a shape that basically followed the curve of the hollowed interior. The curve of the shoulders flowed down into a ½" diameter spigot at each end of the ornament to mate with the upper and lower finial to be installed later. When the exterior was turned to the desired profile and wall thickness it was sanded through 400 grit. Be very careful to prevent trapping fingers in the rotating openings in the side of the ornament. While the finished piece turns slowly on the lathe, spray with lacquer. Remove the finished piece from the lathe.

Finials and Embellishments

Time did not permit turning finials in this demonstration, but Robert mounted with C/A glue pre-turned upper and lower finials into the 3/16 inch holes at each end of the ornament. In Robert's design the upper finial is short and mounted with a screw eye while the lower icicle finial is much longer. The shapes and lengths are design features left to the turner. Robert also pointed out the opportunity to mount embellishments such as bells, miniature Christmas trees, etc. inside the ornament. The holes already drilled through the ends into the interior facilitate such mountings.

Links

For more information on creating friction drive chucks Robert recommended "Making MDF Chucks" by Johnny Tolly on www.turningwood.com/howtoo.htm. For a source of screw eyes see www.meiselwoodhobby.com.

(Demonstration pictures continue down the long column on the right.)

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