Weekend Projects - Twisted stem goblet archive

Friday 15 April 2016

Sue Harker shows you how to create this ornate twisted stem goblet using pieces of pau amarello and ebony

Gallery

This finely turned goblet has been made from pau amarello (Euxylophora paraensis) and ebony (Diospryros spp.) which, I think, contrast well. The cup and base have inserts made from ebony which add interest to the piece. The stem is very thin so I have chosen to cut a double twist spiral. There are several processes to cutting the spiral. Firstly, while the timber is held on the lathe, the outline is drawn and the initial cuts made with a ceramic tile cutting saw which has a tungsten carbide blade. Due to the delicacy of the stem, when the basics of the spiral are cut, the piece is then best finished off the lathe. I made a simple jig, to support the stem, which is held in an engineering vice to hold it steady. The excess timber at both ends of the stem is used to hold the stem securely when cutting the spirals. Various rasps and files are used to refine the shape and a groove is cut down the centre of the spirals to the correct depth with a hacksaw. When you are happy with the depth and width of the spirals they are then sanded, still held in the jig, working through grits 120, 180, 240, 320 and 400 before a finish is applied. There is a lot of off the lathe work required to complete this project but with a little time and effort, the outcome can be quite spectacular.

Tools used:

Bead forming tool

12mm fingernail-profile spindle gouge

10mm fingernail-profile spindle gouge

3mm parting tool

Spindle roughing gouge

STEP 1

Mount a piece of pau amarello measuring 65 x 65 x 100mm between centres and turn into a cylinder. Cut a chucking spigot at one end the correct size for your chuck. Here I am using a pair of callipers, set at the optimum size for my jaws, to size the spigot

STEP 2

Mount in the chuck and use a spindle gouge to roughly shape the goblet cup

STEP 3

Hollow out the centre of the cup to an even wall thickness of approximately 3mm

STEP 4

Sand to a finish working through grits 180, 240, 320, and finish with 400. Apply two coats of cellulose sanding sealer and when dry, with the lathe stationary, apply friction polish and with the lathe running, buff to a glossy shine

STEP 5

Cut a 6mm spigot at the base of the cup and part off

STEP 6

For the base, reduce the remaining timber to a diameter of 55mm and turn the required shape. Drill a 25mm diameter hole in the top to receive an insert. This hole is also used to remount the base to refine the underneath

STEP 7

Sand to a finish, coat with sanding sealer and apply friction polish before parting off

STEP 8

Cut a jam chuck to mount the base using the 25mm hole drilled earlier. True up the underneath, slightly undercutting and cut a couple of 'V' grooves for decoration

STEP 9

Mount a piece of ebony measuring 30 x 30 x 35mm long in the chuck, then drill a 6mm hole approximately 25mm deep

STEP 10

Turn a dished cup with a 6mm x 12mm diameter bead detail for the goblet and stem to fit into

STEP 11

Try the goblet for fit and adjust if required. Sand and polish before parting off – remember there is a 6mm hole drilled through the centre

STEP 12

The remaining ebony is used to cut an insert to fit into the base. Cut a spigot 25mm diameter to fit into the base. It should already have a 6mm hole drilled to receive the stem

STEP 13

For the stem of the goblet you need to mount a piece of ebony (Diospyros spp.) measuring approximately 15 x 15 x 140mm long between centres and turn into the round. Next, you need to cut 6mm diameter spigots at each end and using a fingernail-profile spindle gouge, refine the shape of the stem

STEP 14

For marking the spiral positions on the goblet stem, place the toolrest of the lathe on centre height, and draw four lines along the length of the stem at indexing numbers 6:12:18:24. Draw two reference marks, 90mm apart, evenly along its length then measure and mark lines at 10mm intervals between

STEP 15

Starting at one end, use a ceramic tile cutting saw, or similar, to cut the outline of the first spiral, slowly rotating the lathe by hand as you progress along its length. Take care not to press too hard and snap the timber. For the second twist, rotate the timber 180° from the start of the first spiral and cut as before. This spiral should fit down the centre of the previously cut spiral

STEP 16

Here is a template with red and green lines signifying the two spiral positions which need to be cut. Held up to the stem you can see the different twist positions

STEP 17

The next step in the process is to remove the stem of the goblet from the lathe and support in a purpose made jig held securely in an engineering vice. Use a coarse rasp to cut the spiral grooves deeper and wider. Using a hacksaw, cut a groove down the centre of the spirals – this helps to define the required depth of the piece

STEP 18

Next, you need to work through various sizes and shapes of rasps and files until you have a reasonably smooth finish. Using a wide file, positioned at 90° to the stem, smooth off the square edges of the spirals, rotating the stem as you progress

STEP 19

Using 120, 180, 240, 320, and 400 grit abrasives, hand sand the stem until the desired finish is achieved. The next stage, once you are happy with the spirals, is to hacksaw off the excess timber leaving a 6mm diameter spigot at each end of the piece. Apply cellulose thinners followed by two coats of cellulose sanding sealer. When dry, buff to a shine with wax. Quite a lot of material is removed to achieve the fine delicate spiral stem required for this project

STEP 20

The final step is to glue all the pieces together, with cyanoacrylate adhesive. The delicately turned, double twist, spiral stem goblet should look something like this

HANDY HINTS

1. Instead of a jam chuck, pin jaws can be used to remount the base for finishing the underneath

2. To help with the cutting of the spirals, draw the first twist with a pencil. With each full rotation of the lathe the spiral should have travelled 20mm along the stem – as shown in step 16

3. Don’t worry if the distance between twists is not too accurate, this can be rectified when using the rasps, files and abrasives

4. If you prefer a right hand spiral, start cutting the spiral from the taildrive end and work towards the headstock


Briony Darnley

Tagged In:

Sue Harker , Weekend Projects