Weekend Projects – Simple plywood bowl

Monday 9 July 2018

Plywood is an excellent medium for constructing bowls. When finished it can look very attractive, as long as a few golden rules are applied to construction and turning. The layered laminar construction of plywood can become a beautiful feature of the bowl. There are many different grades of plywood from cheap and knotty construction quality, all the way through to expensive and dense marine ply. The sort of plywood sold at DIY supermarkets is slightly better than the worst construction quality, but still not ideally suited for bowl construction. The ideal plywood for bowl turning is a birch (Betula pendula) plywood, grade A or B. Grade A is knot free and the finest quality; Grade B has a few knots and slight imperfections – the knots may have been plugged – but it is still good quality board. It's usually available in 2,440 x 1,220mm sheets, sometimes cut into 1,220 x 1,220mm or 1,220 x 610mm. These types of plywood are usually only available from timber suppliers.

Tools used:

Bowl gouge

Spindle gouge

Diamond shaped parting tool

Tungsten-tipped tool – optional

Teardrop shear scraper

Square-end negative-rake scraper

Rotary sander

Circular saw or bandsaw

Large button jaws


We are using a 6-layer design developed in Woodturner Studio using its excellent Bezier curve facility to create a beautiful shape. You need Grade B birch 18mm 12 ply for this project. Cut a strip of 1,220mm plywood to 200mm wide and then into 200mm squares


The first step for this project is to cut a 1,220mm length of plywood to a 200mm strip and then cut the strip into five individual 200mm squares. Care should be taken while cutting to ensure the saw blade does not breakout through the back of the plywood. A sharp cross cut blade is ideal here; not a rip-cut blade


The next step is to mark the inner diameter of the bowl to be cut on the squares before the assembly process begins. Now you can mount the squares on the lathe using large button jaws. Using a diamond-shaped parting tool, cut out part-way through the inside of the second level


To avoid breakout of the plywood when cutting out the centres, it's best to only cut half-way through and then turn the plywood square round on the jaws and cut the remainder from the other side


When the centres of all of the levels have been cut out the corners can be removed using a bandsaw or by hand using a tenon saw


Dry fit the levels together to ensure that the cut-outs line up. The sections should look something like this


You will be using a wooden faceplate to fix to the first bowl level. The faceplate must be flat before the gluing stage – flatten the surface with a bowl gouge and check for flatness with a steel rule


The first level is now glued to the wooden faceplate with a glued paper joint. Glossy magazine paper works best using quick setting PVA glue. Centre the first level on the tailstock and apply an even pressure to the glued joint. Leave under pressure for an hour to stop the paper from bubbling


You can now glue up the plywood squares using a quick setting PVA glue. Centre them on the tailstock – I use a round MDF disc with concentric circles drawn on it to centre the levels. The glue sets within 10 minutes and the next level can be glued in an hour


It's important to ensure that the face grain direction of each plywood level is at right angles to the previous level. It's easier to draw an arrow on the side of each level to show the grain direction. Glue up the remaining levels leaving an hour between each gluing


The finished composite should look something like this. I left mine overnight for all the glue to dry out completely before the next turning stage


Mount the wooden faceplate in your chuck and start by cleaning off the rough edges using a bowl gouge. The glue in the plywood quickly takes the edge off the bowl gouge so be prepared to keep sharpening the gouge when it becomes difficult to cut with


Start to establish the rough shape of the bowl. I found it easier to use the bowl gouge in shear-scraping mode rather than bevel rubbing mode. This is a pull cut and allows a smooth contour to be established


Once the rough outside shape has been established, the inside can be turned. The bowl gouge burns very quickly on the inside because of the glue. I used a tungsten-tipped shear-scraper to establish the inside contour on the bowl


The final shape of the inside is established using a teardrop scraper in shear-scraping mode – 45° to the toolrest. The scraper needs to have a flat 90° bevel ground on a coarse grinding wheel. It quickly loses its edge so constant sharpening is needed. Don't forget your work is only as good as your last cut – so make sure the last cut is with a sharpened tool


Since you will next be removing the bowl from its wooden faceplate base, you have to sand the inside now as you won't be able to get back to it on the lathe later. The dust from plywood is pretty awful and not good for you, so ensure that you have good dust extraction working. Start at 100 grit and work up to 320 before the first coat of sealer. Then when the sealer has dried, take it up to 400 grit


The wooden faceplate can now be removed from the base of the bowl. A knife blade positioned on the paper joint quickly separates with a sharp tap from a hammer


Mount the bowl on an MDF cone jam chuck and centre the base on the tailstock with a small steb centre. Position the toolrest at the side and slowly revolve the bowl to ensure it is revolving centrally


The base of the bowl can now be turned down to shape using the bowl gouge in shear-scraping mode as before. Take long, light sweeping cuts to establish a smooth continuous contour shape


Check the bowl thickness throughout using callipers. Try for 3mm wall thickness. The bowl will not be too heavy – yet still strong enough to give it body


Clean up the outside shape with a square-end negative-rake scraper. Take fine slivers to give a mirror-like finish


Clean up the base with a spindle gouge in shear-scraping mode. Try not to cut through the base lamination if possible – the feathering between laminations on a flat surface is not very pretty. The pip under the steb centre can be removed with a flat woodworking chisel later and sanded


The outside can now be sanded. I used an old rubber disc that had previously broken away from its rotary mount. Start at 100 grit and work up to 320 grit before applying the first coat of sanding sealer. After the sanding sealer has dried it can be sanded up to 400 grit


It's now time to apply your preferred finish. Since my wife has an art gallery my pieces for sale get handled a lot so I prefer to use a silk finish acrylic lacquer. Three light coats of spray lacquer – leaving to dry for at least an hour between coats – and then denibbing with either Webrax or wire wool between coats


The finished bowl should look something like this – a bowl to be proud of