26 | Page Oliver Machinery 2019 Lathe
Bug Infestation
Trees are living organisms, and they host many other
organisms, including bugs. Bugs can live inside the bark
and the wood. While the boreholes of the bug-infested
wood give character to a workpiece, the strength of
the infested wood is reduced. The boreholes and
tunnels in the wood create dips on the blank, making it
easier for the woodturner to get a catch. Care must be
taken when processing and turning infested wood.
(Infested Wood Photo Credit: Bernacki & Associates Inc. https://www.bernackiconservation.com/environment-insect-infestation)
Spalted/Rotted Wood
Microorganisms invade and consume the tree when it
is under stress or dies. When different kinds of fungus
reside in the same piece of wood, they can form
spalted wood when the condition is right. Spalted
wood has nice-looking figures, and it is valued by many
woodturners. As fungus creates beautiful lines in
spalted wood, the wood fibers are consumed, and the
structure is weakened, making the blank prone to tear-
outs and blow-ups while it is being turned.
(Spalted Wood Photo Credit: Ed Street - https://www.northernspalting.com/news/spalting-samples/edge-of-spalting/ )
Bark Inclusion
Bark inclusion sometimes can be found in the crotch of
a tree – the location where the trunk/branch branches
off. As the diameter of the branches grows, the
branches fuse together near the tree crotch, and the
bark gets included in the wooded section of the crotch.
Bark inclusion gives the workpiece characters but also
poses challenges and dangers for turning. Bark can
easily detach from wood. If a section of the blank is
mostly supported by the bark inclusion, it can easily
break off under the stress of turning.
Knotty Wood
Knots are not a defect of the tree. However, the knots
make the workpiece more challenging to work with. It
introduces a sudden change in grain pattern and wood
density. The knot and the surrounding area are prone
to tear-outs, and the knot can fly off without warning
when the blank is turned at high speed.
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