Maxprop wrote:
I'm still having difficulty with skew chisels. I seem to get far too many
catches, despite being very careful and keeping the bevel rubbing whenever
possible. I've even taken to honing them after sharpening.
My question: my skews are fairly short and light in weight. Could this be
a problem? Would longer, heavier skews improve my chances of not catching,
or simply make the catches more painful? Any suggestions will be
appreciated.
This is a really difficult problem to diagnose at a distance. But
'whenever possible' is not good enough. I can think of very few
instances when the skew is safely used without bevel support.
The most likely tool size issue is the width of the blade. Assuming that
you are talking about cutting with the edge rather than either of the
points, a blade which is too narrow will make it difficult to keep the
cut away from the point. Larger diameter work (ie the surface is much
flatter than small diameter work) calls for a larger tool. FWIW I do
nearly all my work with a 3/4" oval skew.
Standing in the right place before starting to roll a bead is very
important. Before you turn the lathe on, make a few pretend cuts, making
sure that you can comfortably move the tool from its starting position
with the bevel parallel to the lathe axis, to its finishing position
with the tool handle perpendicular to the lathe axis. A common problem
for novices is to stand in a comfortable position to start the cut, but
then quickly find they are off balance by the time the skew is cutting
into endgrain. It is at this point that the wood requires more force to
cut, and the turner looses control.
Wrist action is important too. You need to be able to roll the tool
comfortably through 90 degrees. I hold the tool handle with the thumb
along the handle and in line with the top of the blade. I find this puts
my hand in a comfortable and controlled position throughout the cut.
Another common problem is trying to cut beads which are too small. The
problem here is that the skew still needs to swing and rotate through
the same wide arc, but on a small bead it has to do so over very little
forward movement. This requires considerable coordination. I normally
start students on beads about 1 inch diameter, and certainly between
1/2" and 1 1/2" diameter. Practice in softwood to begin with where the
forces involved are less. I find 2x4 spruce studs to be good, ripped up
into square stock and just using pieces that are straight grained and
knot free.
Beware of anything that suddenly changes the forces on the cutting edge.
Most common is letting the cut move from the cutting edge to the point.
While a bead can be cut in either position, the way the cut is made and
the forces on the tool are quite different. Switching from one to the
other part way through a cut is a recipe for disaster, though it can be
done with care. Other common problems like this are allowing the depth
of cut to get too big, or not being ready for the extra force required
to cut through the endgrain.
If you loose the cut part way through a bead, take care. Do not drag the
cutting edge back up the cut surface as this will cause a catch if the
edge contacts the wood without bevel support. Until you are very
familiar with the tool, I recommend consciously removing the tool from
the wood, then rubbing the bevel and carefully reintroducing the cutting
edge just behind where you left off. If at anytime the cutting edge
contacts the wood without bevel support and the turner having full
control of the tool, then a catch is almost certain.
Those are most of the common problems I see with beginners. If you can
be more specific about the problem, like exactly what you are trying to
do, and the conditions under which the catch occurs, please provide more
information and I will try to help. Hands on instruction is a much more
effective solution though.
--
Derek Andrews, woodturner
http://www.seafoamwoodturning.com
http://chipshop.blogspot.com - a blog for my customers
http://www.seafoamwoodturning.com/TheToolrest/ - a blog for woodturners