Sanding On The Lathe
Sanding is a very important aspect of woodturning and can make or break the outcome of a turning in my opinion. Especially when turning bowls larger than five inches, sanding is very important.
Firstly, a general rule when sanding any wood is to not sand perpendicularly to the grain because then the sanding lines are more obvious. This becomes a slight issue when turning spindles, which are usually end-grain because it is easiest to sand as the lathe spins, but this leaves sanding marks perpendicular to the grain. Luckily, this is easily corrected by sanding with the lathe after every grit when the lathe is turned off. Doing this after each grit yields a smooth feeling and looking surface.
When I use the word grits, this just means the different roughness of sandpaper. When sanding any wood, or any material for that matter, it is critical to work your way through the various grits. For turning, I often start with 120 grit, then proceed to 180, 240, and 320. Grits of sandpaper go all the way to 3000 but are only necessary when turning glossy items. I generally go up to 320 on bowls, but for smaller objects, I go to 600 grit. Because there are so many grits for sanding, I buy cloth-backed sandpaper that comes with a selection of grits. You can also buy paper-backed sandpaper, but I have found that it disintegrates far quicker than its cloth counterpart, and therefore, it is not worth it despite its cheaper cost.
Turning bowls requires more than just holding up a piece of sandpaper to the bowl if you want to achieve a good finish. Ideally, you will use a sanding pad attached to a mandrel which you can put in the chuck of your drill to spin the sandpaper; the purpose of this is to prevent lines on the bowl, and by having your sandpaper moving, sanding marks are prevented as well as the process sped up. To set up your drill-powered sanding, you will need to buy velcro-backed sandpaper and a sanding mandrel. I use 2-inch sandpaper discs for bowls, and and drill will work, whether it is battery-powered or corded. It is important when using this method of sanding that your lathe speed is relatively low, around 700 RPM(revolutions per minute). Secondly, only one edge of the sanding disc should be in contact with the wood for best results, and this will also prevent the bowl from catching on the drill and jerking it from your hands. An alternative to using the drill is buying a “kinetic sander”, which functions the same way, but instead of the rotational motion of the sanding pad being generated by electricity, it is generated by the rotation of the bowl. It functions by mounting the sanding mandrel in a ball-bearing system attached to a handle. The only downside of this method is that it requires a bit more practice than the drill, but it is my personal preference for bowl sanding, as I achieve quick and reliable results.
