Getting Started with Turning - Using Bowl Turning Tools archive
Tuesday 1 November 2011
WPP shows the cuts you have to make when creating a bowl
So far in our basic turning series, we've shown you the tools you'll need, how to hold the workpiece on a lathe, and how to sharpen those tools - now we'll show you how to use your tools for turning.
For clarity's sake, we will split this part of the series into two parts: this month we will concentrate on bowl turning, and next month on spindle turning.
We'll show you how to use the tools for bowl turning as we shape a bowl ourselves, and will come back to finishing the bowl later in the series.
Standing at the latheStep 1
With your lathe set up and secured to your workshop floor, your workpiece securely chucked and your tool rest in place, it's time to think how you stand at the lathe and grip the tool -
left-handed people need to buy a swivel headstock lathe for bowl turning, and reverse the tailstock/headstock position.
First of all, stand comfortably at the lathe with your feet shoulder width apart. Grip the tool handle with your right hand, and hold this hand against your hip to support the tool. Next, place the gouge on the tool rest. The tool rest should be positioned as close to the workpiece as possible without fouling it, and should be angled roughly in the direction of your cut.
Step 2 & 3
You can grip the tool on the tool rest with either an overhand, or underhand grip, as below. With both grips, part of the hand touches the toolrest to guide the gouge along. The choice of grip is down to you, but the overhand tends to provide more support, and the underhand grip more 'feel'. At the tool rest, the handle of the gouge is held a few inches lower than the tool rest, so the blade points upwards slightly.
Bevel rubbingTurning tools are sub-divided into two types: bevel-rubbing and none bevel-rubbing.
In the tools we'll show you here today, the bowl gouge and parting tool are bevel-rubbing tools.
The term bevel-rubbing refers to the bevel that is ground onto the gouge to create the cutting edge. In practice, this means that the bevel rubs against the timber you are cutting, running behind the cutting edge. With the bevel rubbing, the cutting edge is better supported, creating a smoother, more accurate cut.
Step 4 & 5
However, when making your first cuts on a blank, there is no workpiece surface for the bevel to rub against, so the gouge must be pushed into the workpiece in the direction of the bevel, so creating the rubbing bevel as the tool cuts deeper into the workpiece. Once a reasonable cutting surface has been created, you can feel your way into starting a cut by holding the tool's bevel against the workpiece, and then lifting the tool handle slightly to start cutting, then pushing through the cut with the bevel still on the workpiece. The first cut can be quite daunting, but hold the tool firmly and slowly push into the path of the timber. And be prepared for the tool bouncing if the edge of the blank is a bit lumpy.
Getting startedStep 6,7 & 8
Your first task is to choose a blank - an ideal size is about 230mm diameter and 75mm thick. This is easy to fit to your screw chuck, and neither too big nor too small to make it difficult to turn. Bowl blanks are cut from the tree with the grain running across the blank - exactly where in the tree will determine the grain pattern. To get started, just choose a cheap blank with no defects and regular grain (see panel on timber selection).
Effectively, when turning a bowl, you are making a series of cuts which reveal the shape of the bowl. The gouge can only take off so much at a time, so you cut the timber in stages, both inside and out, as in the diagrams above.
Steps 9 & 10
We will mount our bowl blank on a scroll chuck with a screw thread... effectively a screw chuck. So, first find the centre of the blank, and then drill a pilot hole to a little over the depth of the screw thread, and to exactly the right size. This will be on the inside of the bowl, so is drilled into waste wood
Screw the blank onto the chuck nice and tightly
Then bring up the tailstock with a live centre to provide extra support, tighten up and lock off
Your first cut will shape the outside of the bowl, so present the tool rest at just under the centre of the bowl blank close to the workpiece and angled in the direction of your first cut
Next, and most importantly, check the blank spins without hitting the toolrest. Move the blank fully around 360° by hand. Also, check the blank does not wobble. If it does, tighten it up more securely. The idea is that the face of the blank stays in one plane as the blank spins. Turn on your lathe, using our reference tables in issue 54 as a guide. For a blank of this size, about 305mm, a speed of between 350 and 700rpm is correct
Now for your first turning cut! Hold the gouge as mentioned earlier and with the flute pointing (this direction is perpendicular to the length of the gouge) to 10 o'clock, push the gouge, with a firm grip, in the direction your bevel is pointing. Feel the tool biting into the timber, and cutting on the bottom side, or wing, of the tool. Be prepared for the gouge to bounce around but keep going, and you'll see your cut appear
Steps 16 & 17
Then continue making a series of cuts. As you round off the blank, the juddering should stop. Remember to try and always achieve bevel rubbing by cutting in the direction of the bevel and the flute. Once you have a flat surface, you can start the cut by rubbing the bevel without cutting the wood, only to move the tool handle slightly towards the flute to start cutting. Once you have created a profile on the blank that is parallel to the tool rest, move the tool rest around slightly to the side of the bowl, to cut the full width of the blank
Once the full width is cut, reverse the gouge's flute direction and make a small cut into the back of the blank to create a smooth cutting edge
Next, you need to mark up the front face of the blank
for the spigot that will hold the bowl blank when you reverse the blank and grip it in the scroll chuck (see WPP54). A spigot size of 70mm means marking 35mm from the centre with a pencil - make this mark as the blank is spinning
Next, move the tool rest so it is at about 45 degrees to the front face of the blank, after removing the tailstock, which has to be removed to get access to the front of the blank. Check the blank is secure after the tailstock is removed, and that the blank does not foul the tool rest. Now make a series of cuts angled to start creating the outside shape of the bowl. You are now trying to cut the curve into the outside of the bowl. To do this you must swing your whole body around as you move the gouge forward, so you are creating an arc in the bowl blank, keeping the tool held against your hip with your right hand
Now, with the 6mm parting tool, you can cut the spigot. With the tool rest parallel to the front of the blank, push the parting tool into the blank on the outside of the line you marked previously. You want to create a slight tenon shape to the spigot to match your scroll chuck jaws, so push in at a slight angle, to the depth of spigot you require, normally about 10mm
Steps 22 & 23
Now take the bowl gouge and start cutting the waste from around the spigot, all the while trying to make smooth flowing cuts, as you sweep your whole body around. Make a series of cuts to blend in with the previous curve you have cut
You won't quite be able to get your gouge into the cut created by the parting tool, so once you've removed as much waste as possible from close to the spigot, use your parting tool to smooth
over this area... and now be careful, this is close to the finished surface of the bowl
Final gouge shapingStep 25
Now, with the blank being close to the final shape on the outside, try and make long, smooth flowing cuts from the spigot to the rim of the bowl, creating a lovely smooth curve with a smooth finish. This takes practice, so don't worry if you can't achieve it straight away. Just have sharp tools, and remember your bevel rubbing, and to sweep your body around as you cut. By trial and error, you will find how to create a lovely flowing curve. If the tool comes off a cut part way round, don't worry. Present the bevel to the just cut surface and push the tool into the cut edge and sweep round again to pick up the cut you 'fell off'. It sounds complex, but with practice you will soon get the feel for it
Steps 26 & 27
Next you need to use the straightedge scraper to refine the shape and finish of the outside of the bowl. The scraper is a non-bevel rubbing tool, and so the cutting edge goes straight onto the timber. Move the tool rest to the side of the bowl, near to where you want to use the scraper, and place the blade flat on the tool rest. LIFT THE HANDLE OF THE SCRAPER SO IT IS HIGHER THAN THE BLADE. This is imperative, or else you will have a catch with very nasty consequences. Then gently present the blade to the bowl surface until it cuts, and move the scraper around with a sweep of hand and body, refining shape and finish. The aim is to create as smooth a curve on the outer face as possible
Next, use the straightedge of the scraper blade to refine the bottom of the spigot, and undercut the centre of it slightly. Again, lift the handle and push the scraper into the spigot at one side of the centre. Push in so the centre is cut away first, and then keep pushing until the full width is cut clean
The outside of your bowl is now cut. Many turners finish the outside of the bowl now but as we will be moving onto finishing later, we will now remount the bowl on the spigot we have created. Once mounted, check that the bowl is centred in the chuck by turning it, and seeing if it wobbles. If so, adjust slightly so that it fits properly
Cutting inside the bowlStep 30
With the bowl safely clamped, move the tool rest until it is parallel with the front of the blank. This time make a push cut towards the centre of the bowl, into the hole already drilled to take the screw chuck, again cutting on the bottom wing of the tool. Start off a couple of centimetres from the centre and push into the workpiece, again in the direction of the bevel, and cutting on the bottom wing of the gouge
Keep making a series of cuts until you are about halfway to the outside of the bowl blank
Then start a cut right at the outside edge, and clean up the remaining rough front edge until you meet the part of the bowl you have already cleared out
After cleaning up the front, your next cut is to shape the actual rim. Starting at the edge once again, make a push cut towards the centre, only this time as you push inwards, sweep the handle of the tool away from you slightly, so that you cut deeper into the blank, forming the rim edge
Steps 34 & 35
When you are happy with the rim edge, go back to hollowing out the bowl interior, making progressive cuts which widen the inside, until you meet the rim edge which you created earlier
Mark the thickness of the bowl wall with a pencil. Donâ€™t be too ambitious here. The thinner your bowl thickness, the harder the job, so start off creating a fairly hefty bowl until your skills improve
Steps 37 & 38
Then make a series of progressive sweeping cuts, bringing the bowl thickness down to the required amount. It is perfectly OK to do these cuts bit by bit, cutting about halfway down the inside of the bowl to create a step. Then start cutting on that step to the centre, until the whole sweeping curve is blended in. Note the tool rest position here - it is moved to the inside of the bowl to keep the distance from tool rest to workpiece to a minimum
Bowl centreStep 39
Cleaning off right near the centre of the bowl can be a problem, as the timber is turning very slowly here. The way to do it, is to drop the tool handle just before the centre while you are cutting, so the cutting edge moves down onto the central pip. This takes practice, but again you'll get the hang of it
Now you need to use the round-nosed scraper to refine the inside of the bowl as with the straightedge scraper on the outside of the bowl. Again KEEP THE HANDLE HIGH when making these scraping cuts, and take it easy to avoid dig ins. The idea is to remove all ridges and refine the shape to create a perfect smooth curve
And there we are... the basic cuts for bowl turning with the tools required to create the shape. The main thing with turning is practice, practice and more practice. And take it easy.
Take very light cuts at first until you are more confident. You will soon notice the right feel and sound for your best cuts.
And don't forget to keep your tools sharp! Depending on the timber, turning tools take a lot of hammering, so keep sharpening your edge, perhaps every half hour or so.