Club Meeting: 30 August 2023
Report by: Bill Alden
Kevin stressed that Preparation is important
Start by drawing a plan to scale choosing two complementary shapes. A scale drawing will allow you to take measurements directly from the page.
The next stage is to prepare boards to desired thickness (10-15mm). Mark out your boards with rings a little larger than the plan dimensions and drill the centre to fit the mandrel (12mm) then cut the disks on the bandsaw. Sand the faces . Inner shape for gluing and outer shape for finishing later.
Prepare a thick tenon block for a 50mm chuck and drill a 12mm hole to fit the mandril. Stack the disks for the inner shape in the order on the plan on a mandril with the grain aligned and add backer pieces to support the end disks. The same procedure is followed for the outer shape
Tighten the mandril leaving excess length to protrude into headstock, and fit to a chuck using the tenon block Rough out the shape using 1800-2000rpm to help avoid chipping the edge. Use a shear cutting action on final cuts to get a clean cut with no tear out. Consider the grain direction and cut ‘uphill’ for a grain supported cut. Repeat for both shapes and sand to a finish.
The pieces are removed from the mandrels and restacked back on a mandrel in alternate pieces from the outside form and then the inside form. It could be possible at this point to stack the pieces put aside to make another piece however new top and bottom layers may have to be added. The grain direction is aligned the upper to be hollowed. Kevin then remounted the piece on the lathe in order to take off sharp edges of outer shape.
Glue all joints except the one between upper and lower sections. Use the mandrel as the clamp.
Glue in a dowel into the bottom half leaving a little dowel protruding to fill the bottom of the upper hollowed section.
Using a compression chuck to hold the upper half, drill with a Forstner bit to the desired depth (location of end of the dowel from the lower half).
Hollow inside of upper half. Bear in mind the wall thickness of inner shape.
Assemble, gluing the final joint, and finish.