page14
page 50
Bamboo Journal
Italian Bamboo Rodmakers Association
Let us now determine the length of the indivi-
dual tapes that will form the two shim packs
necessary to plane the groove for the taper we
have selected.
Let us consider a butt taper, for example the
Dickerson 7614. The standard plot with diame-
ter data at stations 5 inches apart is shown in
the igure, upper part. Find the maximum butt
diameter, at the wood insert. The shims in the
guide should be adjusted to plane a groove with
half that depth. Starting from that value, we
must trace a comb of inely separated horizontal
lines, one above the other and spaced vertically
by 3.0 mils. The intersection of each of these
lines with the continuous curve of the taper
gives the length of the single pieces of adhesive
tape. In practice you can ind the values graphi-
cally, but it is painful. Much better is to develop
a software to do the job. I show in the igure,
lower part, the same taper with the intersection
points with the comb of 3.0 mil spacing. Obviou-
sly, the points are more spaced where the slope
of the taper is smaller and they are less spaced
where the incline of the taper is larger. It is easy
to think of the distance between the points as
the width of the steps, all of the same height. It
is immediate to be convinced that steps are
short if the climb is steep, and wide if it is
shallow. At the base of the igure, we have a kind
of a bar code that depicts the steps in two tones
of grey.
The programme (in the debugging phase) also
plots a real size image of the bar code. To it
into an A4 format, the bar code is broken in a
few pieces. Once they are stuck together, they
form a long ribbon as long as the section. I call
this striped ribbon the “Shim Pack Master”. Once
it is stuck to a table, it is very easy to generate
the two shim packs. Moving in a given direction,
mark on the right the light gray-dark gray
transitions. Mark on the left the dark gray-light
gray transitions. The two sets of marks determi-
ne the lengths of the two sets of Magic tapes.
You do not have to bother about inches or
centimeters. Just use the real size images. It is
all there!
Finally, I would like to describe two very useful
tests.
Once you have the two shim packs, you can
“read” them to see if there are mistakes. Proceed
as follows.
as follows.