Weekend Projects - Turned bowl on a bowl archive

Friday 5 August 2016

Philip Greenwood turns two bowls to create this balancing act

Gallery

This design came about when I turned a small round bottom bowl a few years ago. I had a bangle lying around as well and just happened to sit the bowl on the bangle and this has developed into a bowl on a bowl. This project has two bowls balanced on each other, yes they could be fixed together, but this way gives you an opportunity to change the angle of the top bowl and the opening in relation to the bottom bowl. This is more an artistic item than a practical piece, but that does not mean that this could not be used. The upper bowl is made from yew (Taxus baccata) and the lower bowl from walnut (Juglans regia).

The recess in the top of the lower bowl needs a radius similar to the radius on the outside of the upper bowl. A template of the radius of the outside of the upper bowl will help you with the turning of the lower bowl recess. The upper bowl is turned first. This is done just like most bowl turning with the spigot being removed to form the radius allowing this to be rotated at an angle. Once this is turned you will need to make a template of the radius that you need to turn in the top of the lower bowl. The lower bowl is turned the opposite way to most bowls in that the inside is turned first, then the outside. This is so you can produce a holding method to enable you to turn the outside. You can then cut the radius to match the template

you made before. This will match when the bowl is sitting upright. To finish, I have used an oil finish, but you may use any of your favourite finishes.

Tools used:

10mm and 12mm bowl gouge

25mm French curve scraper

3mm parting tool

20mm skew

10mm spindle gouge with a fingernail profile

PPE: facemask, respirator/dust mask and extraction

Timber

Yew 160 x 160 x 100mm

Walnut 95 x 95 x 100mm

Chuck spigot size

We all know the chuck will expand and contract a fair way, my chuck will accommodate a spigot from 43mm right up to 60mm. But the ideal size is 48mm, why is this? If you look at the chuck on the right you will see the jaws touch the spigot completely so you have maximum contact between the jaws and the spigot, but look at the one on the left and you can see large gaps all around the spigot and the jaws only touch on the jaw corners. This means that you will not have maximum contact on the spigot, so less grip on the spigot, plus you will have eight deep marks on the spigot where the chuck jaws have dug in meaning you have no choice but to return the spigot later.

Re-turning the base

How many methods are there for re-turning the bases of items like bowls? There are lots of methods and the one you choose will depend on various factors. The cost could range from £1 for my method to over £900 for a vacuum chuck. As well as the purchase cost, time saved is an important factor, particularly if you are making a living from turning where time is money and a few extra minutes per item adds up over the day. And last, but most importantly, is safety in the workshop. If you ask yourself, “Is it safe to use this method?”, you already have your answer, which is “no, it is not”. I use plywood discs or a dome-shaped bowl covered with anti-slip matting on the outside to prevent marking the turned items. The item is trapped between the discs and the revolving centre in the tailstock, only a small pip needs to be removed by hand after the reshaping or removing the spigot.

Drilling on a pillar drill

Drilling on a pillar drill can be a quick way of mounting your work on the lathe. I use a sawtooth bit of 54mm, this is just a size I have that will drill the hole needed to fit my chuck. Would I use this size bit in a hand drill? In a word, no, due to two reasons: first, my drill would not have the torque to drill with this size bit without risking burning the drill motor out, second, the drill would be very hard to control due to the torque. If you have a small set of jaws then you can use a smaller bit and this could be used in a hand drill. I have a cradle to hold the piece of timber in, this means a piece that is round will sit in the cradle and you can adjust the piece in the cradle so the top face is level. I will then clamp the cradle to the table due to the torque forces involved.

STEP 1

Use a pillar drill with a 54mm sawtooth bit to drill a recess to fit the chuck jaws. This is the best way if the surface is not flat. Hold in the cradle as described in the panel

STEP 2

Use a bowl gouge to rough shape the outside. I use a revolving centre in the tailstock at the start of the roughing out to offer support and added safety. Start with your lathe on a slow speed, you can increase the speed as the blank comes into balance

STEP 3

With the lathe switched off, mark the spigot diameter on the base of the bowl with a pencil, then spin the blank by hand to draw the full circle of the spigot size

STEP 4

Remove some material around the spigot on the base, remember that we need material to complete the radius base later. You have to imagine the curve swiping into the base of the bowl while turning the outside. No need to sand as this will be completed later after the reshaping

STEP 5

Now move onto the upper section of the bowl, this part will be finished to completion. Try to follow the curve round from the base. I have just re-curved the top section over slightly. Sand this top section to completion going through to 400 grit abrasives. Remember that yew is likely to suffer from heat check if the surface becomes warm

STEP 6

Use the skew chisel with the long point towards the spigot laid flat on the toolrest and held horizontally. Try to match the angle on the spigot with the chuck jaws to maximise the gripping power. Use the long point to place a small dimple in the centre of the spigot to aid recentring later

STEP 7

This photo shows the deep spigot I cut to give me stability while turning the inside of the bowl. There is a small gap between the spigot and the chuck jaws; this is so the jaws will sit on the flat at the base of the spigot

STEP 8

Turn the inside away with the bowl gouge; I have removed most of the middle and gone to depth. You need to try to match the outside curve of the bowl while remembering that the outside around the base will change shape

STEP 9

Use a scraper to clean the surface, use this tool in a trailing mode, i.e. the handle needs to be higher than the tool tip to prevent dig ins. Once any ridges have been removed and the curve is smooth start to sand through the grades of abrasives

STEP 10

This photo shows the method I use for re-turning at the base of the bowl. The former is held in the chuck and the bowl is placed over this, this is held in place by the tailstock. Just apply light pressure only, too much and you could split the bowl

STEP 11

Take cuts from the base to remove the spigot, but leave some material around the revolving centre for strength. Start to blend in the curve. You’re looking for a smooth flowing curve running through into the base

STEP 12

A lot of the waste is now removed; take small light cuts only at this stage, you just need to blend the lower part to the top portions, you don’t want a joint line or a change in the curve. Once you think it’s completed, stop the lathe and feel the curve with your fingers to check for any small ridges, remove any ridges and then move on to sanding

STEP 13

Use a small saw to remove the small pip, then sand to a smooth finish. I then oiled this with three coats to achieve the finish I required

STEP 14

Make a template to match the curve on the bowl. It can be easier to make a template to match the bowl curve first then make a negative copy of this so this will be the one I use on the recess. This template is made from thin card

STEP 15

This piece has had a spigot turned on the end; this is now held in the chuck. Turn the inside out with the bowl gouge; you can see the remains of the screw chuck hole. Don’t go too deep and this will be recessed on the top side of this later

STEP 16

Use a curved end scraper to refine the curve on the inside of this, holding the scraper in a trailing mode as before. It’s just as important to finish the underside of items. Take small light cuts, several light cuts will produce a good surface

STEP 17

I am making a recess to hold on the chuck outer jaws, slightly under cut this to give a better grip. Sand through from 180 grades through to 400, checking that all the tool marks have been removed from the surface before moving on to the next grade

STEP 18

Start shaping the outside at this point. The outside at the open end needs to be finished completely as you will not be able to turn this part once held on the chuck. This is just like a bowl, start at the base and work towards the top

STEP 19

This is now held on the chuck jaws, dish first with the bowl gouge and follow this with the scraper. Use the template to guide you on the curve

STEP 20

The template is offered up to the recess and checked for fit. Refine as needed to match the template curve. The closer this is the better the bowl will sit on this

STEP 21

Now is the time to finish the outside of this small bowl. Again look for a flowing curve alone the outside; you can see I am using the side wing just below the tip of the gouge to achieve a searing cut. This is almost at the end of the cut, I don’t want to go much further and catch the chuck jaws

STEP 22

Sand the surface to 400 grade abrasives and then add oil to the surface. Once all the parts are oiled, de-nib and recoat two more times until you are happy with the finish

STEP 23

Your finished bowls should look something like this

Handy hints

1. Wear a full face shield and a dust mask when turning a piece of yew with bark on

2. There are known risks associated working with yew. It can lower your blood pressure among other health problems if you breathe in the dust. Most timber can cause health problems if you don’t take and deal with the issues of dust seriously in the workshop. Here is a link to H&S site that covers toxic timber: www.hse.gov.uk/pubns/wis30.pdf

3. Keep your tools sharp all the time to achieve a better surface finish to reduce the need for sanding. It is surprising how a tool can still feel sharp but is blunt when cutting timber

4. Don’t forget to dispose of oil-soaked cloths safely due to the risks of spontaneous combustion; it normally says this at the end of the instructions on the can, which could be easily overlooked

5. Try to oil your finished items in a dust-free environment as the dust will settle on the wet surface and dry into the oil, which will feel rough when dry

6. The same type of timber could be used on both parts of the project if preferred, however, contrasting timber or dyed, stained, painted or alternative material bases can add an extra visual element

7. A compass could be used to make a template for the main bowl to ensure an even curve both on the outside and the inside. Templates help to highlight any deviation in the curves


Briony Darnley

Tagged In:

Philip Greenwood , Weekend Projects