Stylised Pod Form
Tuesday 14 December 2010
Andrew Potocnik shares his secrets for creating one of his steam bent pod forms
My 'Pod Trio' was featured in a recent issue of this magazine. This article explains how the individual 'pods' are turned, carved and bent. When you break the 'trio' down, each pod is simply a goblet, pushed in a slightly different direction.
Many turners make goblets, so the explanation of my pods should seem easy to understand, I've just taken the concept in an altered direction.
Tools used: 25mm (1in) spindle roughing gouge, 12mm (1/2in) bowl gouge, 6mm (1/4in) bowl gouge, parting tool. 20mm (3/4in) skew chisel and a round-nosed scraper
The first step is to mount the timber between centres and rough it down to a cylindrical form
Next, divide it into three portions: the top, collar and stem. Use a blank of about 60mm (2 3/8in) diameter which is about 250mm (9 3/4in) long. Using a parting tool, segment each of the three parts leaving about 25mm (1in) diameter so that there will not be too much chatter as you continue to refine the goblet
Next, turn the stem down to about 12-15mm (1/2-9/16in) diameter, but this will depend on your chuck. The stem of the form should now fit inside the chuck's centre, into the spindle of your lathe, allowing you to tighten the jaws of your chuck around the collar of the turned form
The next stage is identical to turning an end grain bowl or a goblet. With the form fastened in your chuck, you are ready to hollow the 'bowl'
Most likely, once you've transferred the blank from between centres into a chuck, the whole thing will be ever so slightly off-centre. Trim it back so it is centred and then proceed to hollow it just as you would a goblet or a deep bowl. Here you can see how resting my thumb against the outer surface of the bowl reduces vibration, resulting in less tear-out of wood inside the bowl. Alternatively if you prefer an overhand method of turning, you will find it easier to rest the heel of your hand on the toolrest and support the outside of the goblet form with your fingers, but this is another story in itself
Whilst hollowing the form I rely on the old 'finger gauge' to determine wall thickness, but to confirm assumptions, I use a 'figure 8' calliper to ensure the goblet is evenly thick, or that it is thick enough for anything I want to do in the carving department after turning is completed. For instance, sometimes I like to carve back into the wood to create 'lips' that seem to grow out of the turned form, hence the form needs extra wall thickness. Once hollowing is finalised the exterior of the form is trimmed down to a refined, final shape and any excess material is removed. This means any material required to give the form stability during the hollowing process is eliminated before reversing the form ready for trimming of the collar and stem
To grip the reversed form you can either slip it over your scroll chuck and expand the jaws to grip inside the 'bowl' form...
â€¦or turn a carrier from a stub or scrap of wood to match the inside diameter of the 'bowl' and fit the form just as you would on a jam fit carrier
In either case, slide the tailstock up to the stem to give the piece support and slim it down using a gouge or a skew, depending on which tool you're more comfortable with. Final refinement of the stem is completed with sandpaper ranging from 80 down to 320 grit
Once removed from the lathe it's time to develop some shape to the pod using a fine-toothed jeweller's piercing saw. I prefer sweeping curved shapes to open up the pod. Cut a simple 's' shape from the rim down toward the base which is then refined with files and sandpaper, and maybe a touch up on a belt sander to add flow to the rim so it isn't flat all the way around
To add flow to the overall form soak the stem in water for a couple of hours - you need to experiment, depending on timber type, thickness of the stem and how far you plan to bend it - before applying it to the bending iron. Keep the wood moist either by dipping it in water or spraying it with one of those pump spray bottles - used for keeping plants hydrated - between applications to the hot iron. Apply pressure and gently rock the wood from side to side so you can create a gentle curve. Experience will tell you just how much pressure to apply, how long to hold the wood there before wetting again, but the only advice I can offer is to experiment. That's exactly how I learnt and I don't have the magical formula. You can now make a base for your pod. Draw the shape of the pod's base freehand on a piece of 19mm (3/4in) thick red gum (Eucalyptus camaldulensis) and cut on the bandsaw ready for further shaping
Use a 150mm (6in) belt sander to refine the outer profile of the base and trim the overall shape into a tapered form, flowing from its highest point down to the three outermost points of the piece
Refine the form with a file to ensure each of the three facets flows smoothly - you are aiming for sharply defined ridges along the three 'spines' that run along the base to where the pod's stem attaches
After filing, you need to sand the base with 120, 240 and 320 grit sandpaper. Drill a 4mm (5/32in) diameter hole into the base ready for the stem to fit into snugly - most likely without the use of glue - which enables you to rotate the pod to any angle that pleases your eye. Remember to not overbalance the piece here. Now all you need to do is assemble the piece by putting the various components together