page11
page 47
Bamboo Journal
Italian Bamboo Rodmakers Association
On the inside of the mahogany front and back, I
have glued two false bulkheads made of birch
plywood. The false bulheads have no structural
function, and do not contribute to the “box”
strength. Their sides are tapered to 45 degrees
so to form recesses to retain narrow shims as
discussed below. The operating principle of the
guide is briely described in some sketches. The
guide runs along the edge of the former beam
being pressed against it so that a good contact is
maintained. Simultaneously, the luthier plane
must be pressed inside the guide so that it
contacts the beam and removes very ine,
continuous shavings. At the start, when the edge
is intact, the plane sits inside the guide in the
highest possible position. Pass after pass, the
plane descends between the sides of the guide,
removing thin shavings of increasing width. The
plane stops removing material when the luthier
plane sole reaches the internal birch plywood
inserts. Incidentally, the thin lat surfaces of the
ply have been planed at 16 degrees so to match
the sole slope close to the wall. Once contact is
made, the plane cannot descend any further.
Consequently no more material is removed.
When used on different edges, the system
guide-luthier plane generates cylindrical tracks
with the same depth and with a repeatability in
the order of a thousandth of an inch.
In the next chapter I will describe the method
that I have devised to carve cylindrical tracks
with a depth that varies according to the
chosen taper.
To use the method, it is necessary that the depth
of the groove carved by the system guide-luthier
plane coincide with the maximum thickness for
the section being worked. That is, half of the
diameter of the rod at the wood insert position
for the butt section and half of the diameter at
the ferrule position for the tips. Because the
guide is built with a ixed maximum depth of
cut, it would be impractical to make a new guide
for every new rod section. To cope with this
problem, the guide has a narrow receptacle
along the plywood stop to accept shims that
reduce the depth of the groove. The shims are 3
mm wide, and 50 mm long. At the end they are
tapered to 45 degrees, and these “ears” are
trapped into a 45 degree recesses planed on the
false bulkheads glued inside the front and the
back (see details in some of the pictures).
chosen taper.
back (see details in some of the pictures).