Hi! Today I'll be taking you through the process of rough turning a bowl. Rough turning is done only when the wood is still green or even with just a little bit of moisture in it. When the moisture leaves the wood, it will twist and warp the bowl. Kind of like when you drop some water on copy paper and when dry, the spot is all wrinkled and bubbled out. We rough turn a bowl and leave extra wall thickness, so that when it is dry and warped, we have enough wall thickness to turn it back into round and finish it. Also, keep in mind that it is very important that your wall thickness is even all the way from the lip of the bowl to the bottom. If one part of the wall is a lot thicker than another part, the bowl finds it hard to warp because the thicker part won't move as fast as the thinner part will, so they split apart from each other causing a crack. As far as actual technique goes with bowl turning, there is a lot to learn. I'm not even going to try to explain the old school technique to you because it's just one of those things that you have to teach in person. There's only so much you can learn through looking at a photo, but if you are curious, there are tons of resources on green wood and bowl turning. I would strongly recommend the book "Turning Green Wood" by Michael O'Donnell. It basically covers all the bases from storing green wood, to turning it. Let's get turning!
Step 1: Roughing in the Outside
Now, I always start by using pull cuts to rough in the bottom of the bowl. I eventually will start to bring the back around to the lip and curve it over a little bit. You will get a very clean cut if you cut from the bottom of the bowl to the lip because you are cutting through side grain. Speed also affects how clean our cut is and how quickly we can get a bowl done. I will turn my speed up to the point that my lathe will jump a little and then turn it just a little above that so it will balance itself out. That is usually somewhere around 500-700 RPM. Next, I rough in the shape of my tenon with a bowl gouge and finalize it with a parting tool. If you are turning with a faceplate then this step does not apply.
Step 2: Cleaning Up Your Surface
You'll probably have a little bit of tear out once you have gotten the shape of your bowl and unfortunately it is really difficult for some turners to achieve a flawless surface on a bowl......but we can come close! Now, like I said it is really difficult to explain the technique. It is just something you'll get a feel for eventually. When I try to clean up my surface, I'll sharpen my gouge to get a nice fresh edge and perform a series of really light push cuts. There are two other cuts you can make to achieve a respectable surface. The first a sheer scrape. The second is a finishing cut which is basically a skew cut with a bowl gouge.
Step 3: The Inside of the Bowl
Now we can flip the piece around and hold it in our chuck to work on the inside. I use a heavy push cut to remove wood from the inside of the bowl. Once I feel that I've come close to a final wall thickness, I will turn off my lathe and measure the walls with a set of calipers. I never usually go for an exact thickness. I just make sure that the walls are even all the way across the bowl.
Step 4: Scraping and Drying the Bowl
I use a bowl scraper (sometimes called a french scraper) to smooth out the inside of the bowl and remove material where the walls are thicker. For a final finishing cut, I will turn up my speed as fast as my lathe will go without jumping and shaking and then some, and take some really light cuts with my scraper. Once done, take the bowl off the lathe and write the date on the TENON. Don't write (especially not with a sharpie) on the walls of the bowl because the ink will soak into the wood and you will always have some random date written on the side of your bowl. Drying wood is a touchy process. There are two things that will help the bowl dry without cracking. One is to make sure your walls are even. The other is that you have done something to slow the drying process. the quicker wood dries, the more it warps which will increase your chances of the bowl cracking. So I use an end grain sealer (which is a liquid that comes in paint like form and dries on wood as a wax, sealing some moisture in). After the sealer dries, I will weigh the bowl and write the weight on a slip of paper. Then, I will put the bowl and the slip of paper into a paper bag (the photo above has a plastic bag, but plastic bags cause mold and will spalt your wood, which you might want, but paper bags are a little more breathable) packed with shavings. Every month or so, I will take out the bowl, weigh it, write the weight, and let it sit and air out over night. Once the bowl stops losing weight, it is ready to finish turning. I hope this is helpful to you and I wish you happy turning!