Processing wet [green] wood for woodturning, removing the pith is one of the most important steps you can take to improve the stability of your turning blanks—especially from branches.
. Choose the right section
This guide/blog is aimed at beginners and people looking to increase their knowledge about our craft. Looking at drying your own wood, for your first few goes I would recommend selecting a relatively straight grain log around 150-200mm in diameter. This is a reasonable size log, this time stay away from branch crotch's and other gnarly features as these can be very difficult to dry evenly there is a lot of tension in crotch sections and branched areas.
Once the tension is released they can crack very badly rendering the piece to the burn pile. On with preparing your blanks.
Identify the pith line
The pith may be:
A dark line (oak, ash Yew}
Off‑centre if the branch grew under tension
the pith can often be dead or breaking down
pic 1 this is how I lay out the cut lines to remove the pith so if you look at the top half of the log I hsve managed to get two planks, You need to think, look at the log, the very top plank there is a nice contrast between the sapwood and heart wood possibly a natural piece. The second board down has two flashes of sapwood, the actul pith plank you could get pen blanks,light pulls and so
pic 2 is the actual pith in this piece of Yew. After removing the pith plank you can see the dark brown line this is confirmation that I removed the pith
Split the Branch/small trunk Lengthwise
Slice your chosen log along its length through the first cut line of the pith
plank, I'm using a sled to assist with the stability of the blank
now cut the second cut line
Use a bandsaw.
Ensure the [pith plank] contains all of the pith
Dealing with the pith
The cracking zone, wood shrinks radially [around the rings] much faster than
it shrinks tangentially. Because the pith is at the absolute center of this stress,
cracks [checks] almost always start at the pith and radiate outward.
Remove a [pith plank] and at least 10–15 mm of wood either side of the pith around the pith.
This eliminates the unstable center where cracks originate.
At this point you now have two stable half logs leave them in as long a length possible if you decide to cut them in to blank sized pieces make sure you deal with the blanks on the same day as you cut them
[ROUGH TURN THE BLANKS] if you don't there is a good chance they will split
creating a slightly over sized blank, Leave at least 25mm of surplus wood on either side of your blank this allows you lose the extra length without compromising the size of your piece due to cracking
Seal the end grain
Use wax or waterproof PVA glue. This slows the drying process down and helps prevent checking.
place in a cool dry area you could leave them outside using a tarpaulin to cover from the elements.
The next step, actually roughing the blank out
first step, take your half log and clean up the cut face so that you can attach a face plate or screw chuck .
I use a No 5 screw screw and at least 19 mm 3/4in of the thread is going in to blank,
Think of the position of your screws and how they could effect your finished piece.
Measure the width of your half log, for the sake of this article the width of your log measures 200mm 8in wide, and the length of your half log is 500mm 20in you can now cut your half log into a 200mm 8in square blank leaving you with another blank measuring 250 mm 10in by 200mm 8in,
You can now clean up the faces, get them as flat as possible and ready to accept a face plate , screw chuck. make sure you have no sign of the pith.
Position the grain so that it gives you the most visual impact, taking into account any natural features you may want to keep.
we are going to attach the faceplate to the sawn face of the log this will ultimately become the top of your bowl
The natural grain pattern should be running side-to-side across the bowl.
Really think how the growth rings, figure, and natural features will present themselves once the piece is turned, its worth the effort.
Below is a piece of Laburnum, a small branch section, in this orientation
you can see [middle pic] the flat side of the slab is the top of the small form giving a very striking appearance with two flashes of sap wood on the outside edge.
A hollow form in Sycamore using the striking natural feature of the sapwood in contrast to the heart wood. I must admit probably the most contrast in
Sycamore I've seen.
Rough turning a bowl blank means shaping the outside, cutting a tenon or recess, hollowing the inside, and leaving the walls thick enough to survive drying — usually about 10% of the bowl’s diameter.
1. Mount the blank safely
Lets assume this is your first time rough turning a blank, while the blank is square take a ruler and pencil and draw a line from corner to corner on the sawn side of the log so that you have a cross, there are quite a few different methods of getting your faceplate/screw chuck central, for instance you can use a plastic center finder or use a compass, Attach the face plate or screw chuck to the sawn side of the blank as central as possible bring up the tailstock to support the work piece use it for as long as you can
2. True the outside of the blank
Use a bowl gouge
Remove high spots
once the blank is round, flatten the face where the tail centre is in preparation for making your chucking point
3. Cut the tenon or recess
This is your future chucking point.
Tenon: flat shoulder, crisp dovetail
Recess: clean walls, correct dovetail angle
Always be accurate when cutting your chucking point
4. Reverse the blank
Mount the blank using the tenon or recess. Bring the tailstock up for support, get the surface parallel and running true
5. Hollow the inside
This is where rough turning really happens.
Remember you are creating a general shape, a rough turned bowl for example.
Maintaining an even wall thickness is very important, thinner wood dries quicker than thicker wood, its that simple.
Target thickness:
Bowl diameter 8″ 200mm → wall thickness ~¾″ 19mm
Bowl diameter 10″ 250mm → wall thickness ~1″ 25mm
Bowl diameter 12″ 300mm → wall thickness ~1¼″ 31mm
Even thickness = even drying = fewer cracks.
6. Shape the inside to match the outside
A rough bowl doesn’t need perfection, but the inside and outside should follow the same curve. This prevents stress during drying.
7. Seal the end grain
Use wax, or even PVA glue. End grain dries the fastest — sealing it slows it down and helps prevents checking, Remember a log is essentially a bunch of straws if not sealed well the moisture is released very quickly creating splits, checks
8. Dry the bowl
Options:
Paper bag method
Shavings in a box
Kiln or dehydrator
This is a method I've been using for quite a few years now also I find it easier to work in batches, once the bowl is rough turned I put waterproof PVA on the end grain only both on the outside and inside the bowl I find this way the really hepls to slow the drying process down
I keep it in my workshop until the PVA dries. At this point, I would weigh each form and take a reading with a moisture meter, as pictured below. Then write this information on the tenon. Take the batch of roughed out forms and place them in a container with the shavings from the roughing-out process. Once the shavings have dried out, usually about a week, Take the batch into a spare room and out of the container, place the forms on the floor and out of direct sunlight.
The second pic below is how I would layout the information that is required. Generally the roughed out forms take between 8 and 12 weeks to dry out and become more stable this can vary depending on the time of year. At this point the weight and moisture content become static. I n the room I use the moisture content sits around 10% and is now ready for final turning.
The pic below is how I layout the information. Generally the roughed out forms take between 8 and 12 weeks to dry out and become more stable.
At this point, from experience, Once the moisture content gets to around 10% the weight and moisture content will not decrease any further in the environment it has become as as it can that enviroment. At this point the blank is now ready for its final turning.
If the moisture content is above 10% there is a chance the finished item could move or worse case scenario crack.
If anybody has any questions please email me at
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