Probably most bowl turners generally use blanks cut from green wood. They either make green turned bowls or rough outs to be turned again when dry. Some, particularly beginners, work with dry, seasoned timber, from which a bowl can be made in one session. Drying bowl blanks for that purpose may be easier and quicker than you think!
Most of my own work uses green wood. But in my bowl turning classes I rely on dry bowl blanks that I buy from turning suppliers. My students generally work with a blank of about 7 inches by 2 inches (175 mm x 50 mm), which I find is a good size for a beginner to make a useful small bowl. These blanks cost a significant amount, and sometimes turn out to have defects. So I have begun to make my own. Cutting and drying bowl blanks is a process that I quite enjoy.
Cutting the blanks
I start with a log big enough to yield the size needed. 250 -300 mm diameter is useful, and as long as I can handle, the longer the better because there is always some waste due to end splits. I use a small Alaskan chainsaw mill and my band saw to cut planks. There are plenty of videos on YouTube showing these mills in use, and even how to make them.
My mill is a commercially made one. I attach a plywood support to each end of the log and mount two wooden rails to the supports. The mill slides along the rails as the chainsaw makes the first cut, clear of the pith which is the main source of cracks in the timber. The saw cuts straight, leaving a flat surface that guides subsequent cuts. I use an inexpensive electric saw from Screwfix. It’s self sharpening, which is very helpful, because ripping is tough on the saw and grit in the bark soon blunts it. I haven’t found it necessary to use special ripping chain.
On larger logs, I use the mill to make further cuts, but if the pieces are manageable I take them to my Startrite 352 band saw. On the band saw, I trim the sides to about 180 mm wide, then saw planks 50 mm thick. I turn the log to its best orientation for maximum yield, and can usually go on to saw spindle blanks from the off cuts. The saw is somewhat underpowered, but does a good job as long as the blade is sharp. It’s quicker than the chain saw and makes a narrower kerf, minimising waste. I use a 12 mm 3 TPI blade.
Drying the blanks
I seal the ends of the planks with PVA, then stack them outdoors with spacers to allow air to circulate. After a few months, I cut discs from the planks, cutting clear of any cracks that may have developed. I microwaved a few discs in an attempt to speed drying, but not only was this a slow and labour-intensive process, those discs all split. I allow the other discs to finish drying indoors, but don’t seal the edges or give them any other protection.
Until I tried drying bowl blanks like this. I would have expected the discs to crack. But the process has been very successful. The woods I have used so far are apple and oak (both from standing dead trees, so probably already with a reduced moisture content before planking), ash and cherry. I weigh the discs at intervals until they stabilise, which seems to take about three or four months. I now have about a hundred bowl blanks either fully air dry and ready to use, or well on their way. Hardly any have cracked, and those used in my classes have been very satisfactory. All are similar in size. It may be that the process would not be so successful if the blanks were larger.
Some of the blanks warped as they dried, but I expected this. They are still usable.
Encouraged by this, I sawed some beech and cut some of the planks into discs immediately with no preliminary drying. Most of those discs cracked after about three or four weeks indoors. No surprise there!
It remains to be seen whether the beech planks now drying outdoors yield useful material. But I should be able to cut spindle blanks, if nothing else.
I shall continue to experiment, but at this stage my conclusion is that the discs should not be cut from wet wood. Some preliminary drying is necessary, but the planks don’t have to be fully dry. The total drying time is measured in months, not years.