Manta Ray Bowl
Monday 22 August 2011
Terry Scott shows us how to create one of his signature textured and carved manta ray bowls which is made using a piece of pohutukawa
I initially got the inspiration for turning square items when I was spending time rounding up pieces on the bandsaw - which had been previously cut square - while cutting with the chainsaw. The small cut off corners are often wasted along with some stunning grain and visual effects; these can be used to your advantage if left in the square.
Square pieces are far easier to store, stack, and fillet, and leaving them square also means that you have allowed some tolerance for cracks that will appear when drying wet sawn timber. If you round up at the start and the timber cracks, you need to make a smaller round.
My initial pieces were crudely thick turned works that lacked both form and finish. As my tool skills developed or improved and I found confidence in turning thinner, new ideas evolved, such as pierced or carved corners.
Attending a collaboration in New Castle, Australia, my square turning was further influenced by Neil Scobie and Anna Dawes and their winged vessels. With the attitude that I can always learn something, these types of events have been a never ending source of learning and inspiration.
Hollow forms/vases, pods and bowls all work with the flowing curves of the manta. I was fortunate enough in my youth to have dived alongside these creatures and like to think the memories are what makes the creation of these works so enjoyable.
Tools used: 55° conventional grind chisel, 25mm (1in) oval skew chisel, 35° conventional bowl gouge, 30mm (1 1/8in) scraper
1. Quality live centre
2. Reversing live centre
Choose a piece of timber that is tight grained and free of defects. For this project I used pohutukawa as I knew it wouldn't shatter, cuts cleanly, and carves and textures well. The downfall is that it is not always stable and may move. Choose a piece of timber that measures 165mm (6 1/2in) square x 75mm (3in) deep.
I have also learnt that having the blank dead square and parallel makes turning the wings easier. By double checking the diagonals, you can be sure you have the measurements spot on. Find the centre, mark with a bradawl, then drill an 8.5mm hole, 25mm (1in) deep to take a screw chuck. If you have a swivel head lathe, check that the tailstock and headstock are perfectly aligned. Mount the pre-drilled blank on the screw chuck of your choice; I prefer a one piece screw faceplate as the seating area is better. Bring up the tailstock; you will see I have a heavy duty live centre as this is guaranteed to run true and it will take a hiding
Always rotate the work before turning the lathe on. Take a freshly sharpened 10mm (3/8in) 35° fingernail-grind bowl gouge and present to the work. You need to cut the underside of the bottom wings first. Keep the handle well down as you want the timber to come down onto the cutting edge
You are turning cross grain as you cut the valley between wings and bowl. You need to cut downhill from both the wing side and the bowl side to prevent the tool picking up the end grain. At the same time as starting to form the wings you can shape the foot by turning the chisel on its side. The foot will be larger than the normal one-third diameter of a bowl, as this will be used to create the feet later
The wing underside cut and shaping the bowl now need to be blended together. Have the chisel handle down and cut above centre. As you come to the wings, lift the handle and rotate your right hand all in one movement
Use a glue stick to check that you have a fair curve. Any flat spots will make the job harder when you reverse the piece and the flats will continue to show up after texturing. Remember, placing texture on work will not hide bad form. It will look worse if not right
Once you have a fair curve, check with a straight edge that the wings are higher than the planned base or feet. Of course, you may want the work to sit on the wings
Use a black felt tip and your fingers to mark the thickness of the lower wing and where the upper wing will be. This shows the area you are about to remove between the two lines
To turn the wings very thin, down to 2mm (5/64in), I have developed a support system to prevent me losing the tips. I cut dowel braces and hot melt glue them from wings to body, allowing room for the chuck
This next step should only be attempted if you are confident with the skew and understand how to approach the work. I have tried many different chisels, grinds, and shapes but as two of the wings are end grain, I have shattered many a work. Set the toolrest as close to the diameter of the work as possible and about 15mm (9/16in) above centre. Hold the skew with the handle well down at 45 to 50°. The reason for this is you want to cut across any end grain if you can. A spindle gouge doesn't work as the further you go into the 'V' the easier it is to have a catch, as you have two sides to the flute. Check and double check before turning on the lathe. There is nothing worse than the toolrest walking into the work. You want to cut with just 2mm (5/64in) of the tip of the skew and still rub the bevel. Once again, you have to work the cut from side to side
Don't push the cut or you will push the bottom wings off. Get the thickness of the lower wing nice and even and the shape of the upper wing as another fair curve
Deep in the cut is where you can have a catch, as you are tempted to bring up the handle of the skew. Now, turn the piece over. Make absolutely sure that when you chuck and flip the work around it will run dead true, or the wings won't be even. I use a Vermec chuck. This has a bearing, so on some works I actually turn with two chucks: one on the headstock, and one on the tailstock
It is imperative that the headstock and tailstock line up before doing this. Mount the chuck on the tailstock, bring it up to the work and tighten up
Remove the wood from the screw chuck, reverse, and you're good to go
Bring up the tailstock. Turn these at 2,200rpm as you want the work to be held firmly. I never trust the chuck on its own
Add more hot melt glue and struts to support the top wings
Cut the top wings just as the underside was done, staging the cut so you don't cut deeply into the end grain. The wing thickness needs to be the same as the lower wing, and also a fair curve
You want the visible outside curve of the bowl in the centre of the work to have the appearance of flowing through the wings, so, with the aid of the butt end of the Vernier callipers, check the distance
When the sides of the bowl and the rim line up then you can hollow out the bowl as normal. Change to a 55° grind bowl gouge
Check the depth with a depth gauge and the wall thickness with figure 8 callipers
Make the finish cut with a scraper sharpened like a skew. Start sanding the interior section with 120 grit and then apply a generous coat of oil to the surface and continue to sand with 240 grit, wipe out the slurry, and repeat for 320, 400, and 600 grits. If the paper gums up you can clean it with a soft wire brush. There are eight wings. Study each as any chips or flaws will determine if that wing may become an up or a down. Mark the ones you want cut off and use a Mini Arbortech or a Merlin carving cutter to remove the dowel supports and shape the wings as much as you can. All of the upper surface of the work can now be sanded to the same level as the inside of the bowl. To get to the bottom wings, flip the work over and use either a chuck to hold the rim - a jam chuck or friction block - and bring up the tailstock, ensuring to keep it well clear of the work
Change the spigot into a ring that will be carved away to form the three feet. Use a contour gauge to make sure the bowl's curve continues through the ring and across the foot. Cut away the unwanted downturning wings
Alternative cutting methods
Terry is an exceptionally skilled practitioner and has developed a way of turning that works for him. Here is an alternative method; it is safer in the cutting process of the wings and does not require the use of a skew. Using this method, however, will require a little more time in finishing the wings off later on
Create the up and down wing section as before. If you intend to create a thin wing section then use the four-dowel support method that Terry shows
Once you are happy with the wing forms, determine which wings you want up and down, mark the waste sections then index off the chuck to keep it in one position. Use a power carver or sander to remove the wasteâ€¦
â€¦a mini 50mm (2in) carver or sander affords a lot of control, but larger sanding discs and carving wheels can be used in an angle grinder. The smaller carving and sanding discs afford you more control
Once the wings are formed, use hand or small powered detail sanders to refine and blend in the flow of the wing curves and the surface of them
The bulk of the underside of the bowl can now be sanded and, using the lathe index, mark out a grid and parallel lines that will be used as a reference for the texturing. Keep the tape around the bowl rim as protection. I used a plastic barbeque plate that will bend around the formed wing to mark an even curve coming exactly to the tip of each wing to separate different patterns of branding
Using masking tape assures you of a crisp line while burning the edge of your first pattern
Ensure to get an even texture and to cover the whole area with texture, as when you add a finish the smooth areas, if left between the textures, will be highlighted
Once the texturing is finished on the top face, flip the piece over and again hold it with the larger chuck around the bowl rim. Mark out the feet with the set out template. You could do this on the lathe with the index but I like to study where to place the feet so the work is stable and doesn't tip over. Alternatively, you could use a pair of compasses by taking the radius of the foot circle, stepping out around the circumference, and using three of the six points this makes. With the Mini Arbortech, blend the area between the feet. Because you spent time making sure the curve between the bottom and sides was right, this part is made easy. Using a glue stick, you can be assured of a fair curve and can sand all of the foot area
The underside of the bowl can now be textured. This follows the lines drawn earlier to ensure a nice, consistent pattern. The layout for the pattern on the underside of the wings can then be drawn. Once again, masking tape will help you to get nice clean lines. Check the set out so all the curves are similar. The bowl's underside is now complete
After all branding is done use a small wire brush to remove any carbon; this helps to enhance the detail and means the Indian Ink can penetrate the surface
The build of special effects begins by first dry brushing in copper. These may be followed by airbrushing translucent colours to give the piece a sense of movement. The pohutukawa manta ray bowl is now complete