Monday 9 July 2018
I am surprised that segmented turning is not as popular in the UK as it is in America. I can't tell you the joy I had when I created my first composite bowl from planks of timber. I quickly realised that I could make beautiful objects, of any shape or size, that were no longer dependent on the size of the piece of wood I was turning – I was only limited by my own imagination.
Segmenting turning looks very complicated for most turners, but it isn't, so this article shows you how to create a simple bowl with a few tools and basic equipment.
My first bowl, 10 years ago, was made from some off-cuts of beech (Fagus sylvatica). I still have it after all these years – it started me out on a new career. I hope this article will also set you on a journey into segmented turning and that you will have as much enjoyment from creating unusual segmented objects as I have had.
15mm (5/8in) bowl gouge, 25mm (1in) scraper, internal shear-scraper and a parting tool
I started with a plank of 25mm (1in) plain ipe (Tabebuia serratifolia) hardwood decking that I had left over, but any hardwood will suffice for this project. Ipe is an oily wood the colour of walnut (Juglans regia), straight-grained and easy to turn. The thickness is not critical as long as it is uniform
If your decking or hardwood is already planed, all you will need to do is to cut the strips using a circular saw to the widths shown for each segment level. The dimensions are not critical as long as they are larger than shown on the cutting list
The bottom of the bowl is solid. When I first started segmented turning I made the bases out of segments but they always separated as the wood dried and moved. So most segmented turners use a solid base. Start by gluing the base onto a salvaged piece of wood already set up to fit the chuck jaws; this saves wood and gives more room to part-off when finishing the piece
The segments are then cut on the mitre saw. A dummy back-plate has been added to the mitre-saw to stop the segments flying off, as well as an end-stop to gauge the segment lengths. Set the mitre saw to 15 degrees. It may be worth cutting six segments – a semi-circle – with some scrap wood to check the mitre angle. A very clean cut can be obtained by slowly lowering the spinning blade onto the wood. Remember to keep your fingers out of the way
Clean off any burr on the edges of the segments and then glue them together. I have found that Titebond II is the best for gluing end-grain. Just rub the segments together, hold them in position, and then after a couple of seconds, the glue grabs. Some segmented turners clamp their segments together under heavy mechanical pressure to close any gaps. I found that these stressed joints eventually break, with costly results. The 'grab method' doesn't put the joints under any strain
Glue the segments on a sheet of polythene on a thick piece of glass, but any flat surface will do. Once a semi-circle of segments has been glued-up, check the segment alignment with a rule
Any slight imperfections can be sanded out before gluing the semi-circles together
Clean away any glue residue on the sides of the first level by rubbing them, under pressure, on 80 grit sandpaper
In order to centralise the levels during gluing-up on the lathe, I made a backing plate from MDF with concentric circles drawn on it for the alignment of the levels, but you can also do it by eye, if you choose. The first level is glued-up and positioned on the lathe between the base and the back-plate. When it has been centred the tailstock is adjusted to clamp the levels finger tight
Once the glue has dried – usually after about eight hours – the level has to be trued. Use the bowl gouge on its side in shear-scraper fashion to true-up the level
Then check the level with the aid of a metal rule
The levels are then gradually built-up, aligning the segments brick-work fashion. True up each level before gluing the next level. To add a bit of interest, a feature-ring of veneers has been included in the design. Glue two white veneer sheets together – separated by a dark brown sheet – and put them between the fourth and sixth levels. Dampening the veneer with a wet cloth before gluing softens the veneer and makes it much easier to sandwich the pieces together
Complete all the levels and the finished composite bowl should look something like the one shown here. Now the exciting bit – to create your own beautiful bowl from the composite made from a plank of wood
It is easier to start on the inside while there is still some thickness in the walls at the top of the composite bowl. The bowl gouge does not work inside a composite bowl; the edge quickly gets burnt by the hard glue and tends to tear the grain. So the rough edges on the inside are first of all removed using a scraper on its side at approximately 45 degrees. Take light cuts, initially at a medium speed, until the segment edges are eliminated
Once the inside is smooth use a shear-scraper with a tear-drop blade to create a smooth contour. Again, it is presented at a 45 degrees angle to the wood. The lathe can now be speeded up to enable delicate whispers of shavings to be made
The outside can now be cleaned up using a bowl-gouge on its side in shear-scraping mode, which gives a clean cut without undue stress on the bowl. Start at the top to get the shape you require. You can still go back to the inside at this stage if the shape isn't right, but you can't go back to the top once you start to reduce the thickness from the lower half of the bowl; vibration will occur at the rim, spoiling the finish
Once you are happy with the top you can start on the lower half. First of all smooth out the edges of the lower levels, then form the base by taking long, sweeping strokes to give a smooth outline
Sand the bowl with an electric drill fitted with a 50mm (2in) sanding disc. Start at 80 grit and work up to 400 grit, first the inside, then the outside. There were some small tears in the grain on the inside that needed some localised sanding treatment, but they were quickly eliminated
If the wood is quite oily, use finishing oil. Let the first coat dry for 24 hours before burnishing it with wire wool. Two coats should be adequate, then the bowl can be parted off the lathe and the base can be cleaned up. The bowl takes about three hours to make, but in stages spread over a week to allow for the glue and finish to dry. The bowl is now complete