Making a bowl blank (the roughly bowl shaped billet of wood) ready for turning on a lathe is not as simple as it is for spindles like chair legs. A lot of wood needs to be removed across the grain and it can't be split or shaved. It's certainly possible to use an axe, though the shape of the blank makes it more difficult, but it quickly improves your axework and appreciation of a sharp axe. Do remember to count your fingers when you finish!
Unless you are a purist, or particularly fond of axe work then using a power tool to prepare the blank will appeal. I'm not a purist, I just happen to like using a foot powered lathe for turning.
But which power tool to use? There is such a selection of boy's toys to choose from. The two most widely used are probably the bandsaw and the chainsaw. If you have a good quality bandsaw then it's got to be sensible to use it. I don't have one so an excuse to buy one seems a perfect opportunity to gain another toy. But, and it's a big one, I don't have space in the shed for a big bandsaw of the size and power I'd need for a range of jobs including big bowl blanks. I do have a cupboard full of chainsaws, and a good understanding of how to use them safely, as I teach chainsaw courses on occasion and do rudimentary carving with them, which is more than I do for bandsaws.
Since the chainsaw is inevitably used to fell and cross cut the logs in the first place, extending it's use to shaping the blank doesn't seem too much of an unnecessary use of power tools. The two saws I have most suited to this are the Stihl 240 and a McCullough 335. The Stihl is a professional saw that I use very heavily for a wide range of tasks whereas the McCullough is more of an amateur saw, but with it's small Oregan bar (I fitted this) and narrow 91vg picco chain it's actually a very good carving saw for the price if a little plastic.
Here's how I use the chainsaw to fashion a bowl blank (not that I'm an expert). I start by using a froe to cleeve the log in half (you could use the chainsaw for this as well). Then the first cut is down the cleft surface to flatten it and to remove the pith of the log. The second cut is to flatten the base and needs to be parallel to the first cut, I do this by eye but you do need some experience of chain saw use to be able to cut accurately. I use a clamp on a stable workbench for these cuts. It helps ensure accuracy as well as making the job quicker and safer. The need to make accurate felling cuts for felling trees will teach you this so I can't recommend taking NPTC chainsaw qualifications highly enough if you plan to be a safe and effective chainsaw user.
To finish the first stage of the bowl blank I knock the corners off the blank with the saw. More care is needed at this stage since it's very tempting to use the tip of the bar to make the cut's. I do this but you need a good understanding of how kick -back occurs in chain saws.
I'm tempted to cover this here but at the risk of boring you to tears let's just say that it's the combination of Newton's third law - every action has an equal and opposite reaction - with the effects of levers.
So if the chain driven at full power by the motor is suddenly stalled by the wood something has to move, if it isn't the chain then it's either the wood or the saw or a combination of both creating a dangerous situation. The length of the bar is a lever which further increases the force of the kick-back. So for this purpose I use a small, low power, light weight saw with a short bar and plenty of anti-kick back features to help prevent the chain from jamming in the kerf.
Once the corners are knocked off it's possible to continue using the saw as a carving tool to complete the blank. I have done this, but recently I've switched to another tool with similar characteristics but a lot of advantages over the petrol chainsaw. It's an angle grinder attachment called a Lancelot. A small chainsaw chain is fitted in a circle around a pair of aluminium discs and then fastened as standard to the angle grinder. It takes a bit of getting used to but once you do it's very quick and easy to finish the bowl blank using the Lancelot. It's much lighter than the chainsaw and the lack of a long bar reduces the leverage effect of kick-back. The grinder safety guard is still used and this helps to prevent placing the chain in positions where it might jam in the wood. If it does jam then the chain tends to slip between the discs like a simple slip clutch which removes any kickback.
It only takes a couple of minutes to complete the bowl blank to the level needed to put on the lathe. It's quite possible to use the tool to make the bowl. I made a couple while getting used to the tool, though it's nowhere near as enjoyable as using the lathe due to the excessive noise, dust and vibration so I don't recommend it. A low power, low noise grinder or a cordless grinder might make it more socially acceptable but none of these tools are going to be subtle.
Unfortunately for the moment I seem to have talked myself out of an expensive bandsaw. but in consolation I've gained another chainsaw related toy. There is quite a good write up of the King Arthur's tool range of chain attachments for angle grinders on the classic hand tools website, though I think I bought mine from a national network of stores like machine mart. I imagine that the performance is very similar to the arbortech which is a form of circular saw as an angle grinder attachment. I have one of these now and plan to compare them before too long, but if you are familiar with chain saws and chains then the Lancelot seems a very good choice to me.
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