magic star cutter
instructions
The Magic Star rod was described in issue #98 of The Planing Form
by Wolfram Schott. According to Mr. Schott the rods made using
this method of hollowing were produced by Vangen and Carlson
in Norway through the middle to late part of the last century.
Each strip of the Magic Star section is shaped like an inverted “T”
resulting in a cross-section with a set of “spokes” or that support the
outer wall. In the article Wolfram suggested that it might be worth
producing the tooling to recreate this design on the Morgan Hand
Mill. Bill Lamberson, a Hand Mill user, approached me to design
such a cutter. It sounded like an interesting project and a method of
hollowing different from the regular hollow fluting cutter I provide
for the Hand Mill.
I agreed to make several prototypes to see how well they worked.
We tried one as did Bill and two other users and they worked well.
Magic Star Cutter on Handmill
As a result I decided to make a production model. I thought that a
(photo 1)
slight variation on the original prototype where both a triangular and
square insert could be used to remove different amounts of bamboo
while varying the glue seam area would provide interesting options for the rodmaker. In addition, I
wanted to provide a method to vary the width of the “spokes” of the inverted “T” that would provide
some interesting variations in rod design.
One Hand Mill user, Brent Nickerson, who tried one of the prototypes was interested in working
on the development of the new style I had in mind. Brent is very creative, is a retired engineer and
machinist, and is a very capable computer CAD user. We worked together to design the new Magic
Star Cutter(photo1).
If you look at the end of a bamboo section cut with the Magic
Star Cutter you will see the center support “spokes” along
with the bamboo removed on either side(photo 2). The
Magic Star Cutter head also is designed to vary the width of
the “spokes” from approximately .030” to .065”. Naturally,
the depth of cut is also variable depending on the amount
of wall thickness desired. The amount of weight reduction
depends on the combination of the “spoke” thickness and
the wall thickness.
1
2
1. square cutters 2. square cutters 3. triangle cutters
4. triangle cutters (photo 2 )
3
.030
.065
.065
.030
spoke
spoke
spoke
spoke
4
thickness
thickness
thickness thickness
General Magic Star Hollowing Information
The body, the carbide insert holders, and fastening screws are all stainless steel to ensure that the unit
won’t rust in humid climates. The unit comes with two 1/4” IC (Inscribed Circle) triangular carbide
insert and two
1/4” IC square carbide insert both with an 11-degree positive rake for good chip
clearance. Both insert styles have a 1/32” tip radius. The Magic Star Cutter attaches with two 10-24
by 3/4” button head screws that are provided, in lieu of a cutter head. I am also providing a brass brush
to brush any loose bamboo off your strips after hollowing.
1 (Magic Star Cutter)
Because the Magic Star Cutter inserts are lower in relation to standard
insert cutter heads the regular length hold down shoe won’t properly
hold the bamboo. Therefore, I am providing a longer 6-strip shoe
with each cutter along with an extra screw to attach it to the hold
down arm. If you also want to hollow 5-strip or 4-strip rods you will
need a longer shoe for each. As with the regular shoes they must be
centered to properly hold the bamboo strips. I think that it is easiest
to move the plane with the shoe attached to the end of the anvil, drop
the shoe down, and center it on the anvil itself(photo 3).
The Magic Star Cutter is a new design for me and even though I have
made sure the cutters and concept works I haven’t made any rods
using its principle. Therefore, I don’t have any recommendations
Longer hold down arm (photo 3)
based on its use as to “spoke” thickness or wall thickness. Certainly,
one consideration to keep in mind when hollowing is to use a
combination that leaves enough glue surface on the edges for proper adhesion and joint strength.
Below is a CAD drawing of a theoretical “spoke” cut with both a square insert and a triangle insert
showing the relative material removed with each(photo 4). It’s evident that the square cutter will remove
the most material, however, the square cutter glue seam is about 80% of the glue seam cut with a triangle
cutter so the joint glue strength won’t be as great.
2 (Magic Star Cutter)
A rod made using the Magic Star Cutter will have to be increased
in diameter to compensate for a reduction in stiffness compared
with a solid rod. Experimentation with your individual tapers will
give you an answer to the hollowing/stiffness ratio.
Measuring wall thickness with square cutters.
(photo 5)
Measuring wall thickness with
triangle cutters. (photo 6)
Based on my experience with hollow fluting a butt wall thickness
of .060”-.070” for trout rods and a butt wall thickness of .075”.085” for steelhead and salmon rods should be adequate. However,
with the extra support in the middle I would think that the wall
thicknesses could be less particularly with bigger rods. You
should also be able to hollow tip sections. This may not seem
important but reducing the weight of a tip can have a significant
effect on how light and lively a rod feels. You can experiment
with different combinations to determine whichever is best for
your application. Since this is a new product I would appreciate
getting feedback from users on their experiences.
When you rotate or change inserts make sure that the pocket
behind the insert is clean and free of debris. As with other carbide
inserts it is a good practice to mark the back of the insert with
a felt tipped pen to keep track of usage. When you mount the
inserts make sure that they fit well in the pocket before tightening
the screw.
Depending on which Magic Star Cutter inserts you are using
will determine how you measure the wall thickness. If you are
using the square insert you can measure the wall thickness directly with a micrometer or caliper(photo
5). However, if you are using the triangle inserts you will not be able to read the wall thickness directly
because the bamboo isn’t flat on the sides of the spoke. I suggest that you use a trial piece of bamboo, cut
it part way down, and shave off the lip so you can measure the wall thickness. As an alternative you may
also be able to measure with a caliper from the end and next to the spoke if the tips are narrow enough to
fit into the bottom of the groove(photo 6). Once that is established you can adjust the head to the depth
you want, set the hard stop on your plane, or make a reference note of the depth setting on the plane.
As mentioned before by loosening the screws that hold the carbide insert holders and moving them side to
side you can vary the width of the spoke from approximately .030” to .065”. It’s also possible to set them
so that the chimney thickness is somewhere in between as long as you keep the cutter inserts centered.
Here’s how. First, with the insert holders locked into the position where they are as close together as
possible you must use a feeler gauge to determine the width of the gap between the carbide inserts. Let’s
say for this example they are apart .030”. Then let’s assume that you want the inserts .046” apart or each
insert must move .008” off center. Add a .008” shim to your feeler gauge so it is .038” thick, loosen one
insert holder moving it enough so the .038” feeler gauge will slip in, and tighten the holder against the
gauge. Now add another .008” shim so the gauge is .046” thick, loosen the other insert holder so the feeler
gauge will slip in, and tighten the holder against the gauge. The carbide inserts are now .046” apart and
centered. You can set the inserts apart at any dimension between .030” and .065” using this method.
3 (Magic Star Cutter)
Star Hollowing Butt Strips
I am going to give instructions for a level hollow except for a short transition area between the hollow
and ferrule. There is the option of setting a taper on the bed to provide a tapered hollow but I will
only discuss cutting a level hollow. From my experience it is essential that hollow fluted rods be
solid under the ferrules so I am assuming this is true with Magic Star hollowed rods also. To do
otherwise is to risk delamination of the glued rod in the ferrule area.
The Magic Star Cutter is used in lieu of a regular cutter head. Hollowing is done after the individual
bamboo strips are finish cut. As with any other strip cutting on the Hand Mill you will always start at
the butt of the strips and cut towards the tip. You will also leave the uncut butt section with the attaching
hole on the strips to provide a means of attaching the strip to the anvil. The tip of the butt must end
short of the end of the anvil. If you were to run the cutter over the end with the bamboo jutting past the
end of the anvil the bamboo would most likely be broken.
In this description I am going to assume that you want the rod butt hollow to the bottom. If this is not
the case you could start your hollowing part way up the butt. The advantage to this would be to have
a solid section under the reel seat. I prefer to have the butt entirely hollow except under the ferrule
since it saves substantial weight. If you are concerned about having hollowing under the reel seat
once the butt is glued you can carefully hollow out the bottom 1/2” and glue in a dowel for support.
If you do this I recommend cutting with an end mill instead of a drill since the end mill doesn’t put
radial pressure on the bamboo.
In this illustration I am going to assume that the butt size will be a 13/64” ferrule and that it will be
a level hollow until the transition before the ferrule. I am also going to assume that there is a .003”
allowance to leave the bark on the bamboo. A 13/64” ferrule station is .203” plus .003” for a total of
.206” and since we are working with 1/2 of the height this leaves the strip .103” high.
In this illustration the wall thickness will be .070”. Subtracting the .070” of the wall thickness from
the strip height of .103” leaves .033”. This is the amount the bamboo strip height must change in order
to have a solid section under the ferrule. We want a tapered transition from the hollow fluting to the
ferrule so that the fluting doesn’t stop abruptly.
The “spoke” width can be any width from .030”-.065”. On trout rods the narrower width should provide
enough support and the section will be lighter.
It is my suggestion that you experiment with an extra strip before starting with a finished set of butt
strips. Mark on your butt strip with a pencil where it is .103” high for the ferrule. I want you to leave
2” of solid before the ferrule to insure that your butt will be solid under the ferrule. Therefore, mark
another spot 2” down the butt towards the bottom from your original mark. This will be approximately
where your hollowing ends. Assuming a taper of .030” per foot on a finished rod the height here should
be about .100”. Therefore, we want the bamboo to drop .030” between the end of the fluting and where
the section will be solid. The easiest way to achieve this drop is with the swelled butt shim kit.
Before beginning your hollowing process you must first make sure that your butt-finishing anvil is
installed. Then you want to set your butt anvil with no taper using your dial indicator. I suggest setting
it .010” above the base. Once you have the anvil level you can proceed to the next step.
4 (Magic Star Cutter)
The taper from the .070” hollowing to the solid will be done over 2 1/2”, the distance between the anvil
hold down screws. Start by laying your bamboo strip on top of the butt-finishing anvil with the tip end
of the strip short of the anvil end. Fasten the butt strip
down using a regular screw. Mark with a felt tip pen on
the anvil where your bottom pencil mark closest to the
butt is located (photo 7). Make a note as to which butt
hold down station you are using.
Remove the bamboo strip. Loosen the anvil enough so
you can slide the .030” shims under the anvil between
the hold down screws. (If you have the precision ground
washer style shims you will have to remove the anvil
to install the shims.) Install the .030” (or .032” ground
Butt strip markings (photo 7)
washers) shims from the swelled butt kit starting at the
right hand anvil screw and continue up the anvil until
you reach the anvil screw before your mark on the anvil.
Tighten all of the anvil screws including the ones where there are no shims. You will now have shims
starting at the bottom (right hand side) of the anvil and continuing to the anvil screw just before your
anvil mark. The balance of the anvil to the end will be tight against the adjustable bed. This will allow
the tip of the bamboo strip above the bottom pencil mark to be pushed below the Magic Star Cutter by
the hold down shoe.
For this example I will use the Magic Star Cutter with square inserts together as close as possible. Mount
your bamboo butt strip on the anvil using the previously determined station. With the adjusting screw
run your hollowing attachment up until it is well above the bamboo when you set the Mill on the base.
Set the Mill stop so that the hollowing tool will start cutting where your tapering cut began.
Adjust the Star cutter down until it just touches the top of the bamboo strip near your hold down screw
. If you were to adjust the carbide insert to touch the bamboo between the end of the shims and the tip
of the butt the setting would be too deep.
Lift the plane up and adjust the cutter down about .006-.008”.
Run the plane down the bed making your first cut. Examine
the bamboo strip. You should see the beginning of a spoke
centered on your strip and gradually diminishing as you go
up the strip. Even though you are maintaining a constant
wall thickness of .070” the amount of bamboo you remove
will gradually lessen as you move up the strip. From our
observations a cut in the .005”-.007” range works well. The
cutting goes quickly and easily because you are not removing
much material.
After making 3 or 4 passes measure your wall thickness with
a caliper or micrometer (photo 8). You will probably want to
remove your bamboo strip from the anvil before measuring.
5 (Magic Star Cutter)
Measuring wall thickness with
square cutters. (photo 8)
After determining the wall thickness you can calculate how much deeper you need to go to reach the
.070”. On the last two or three passes reduce your cuts to .002-.003” in order to clean up your cuts
and to reduce splinters. When you first cut all the way to your pencil mark you can make sure that
the hollowing is ending at the correct place on your strip. If it is not readjust your procedures so that
it does ending about 2 inches from the ferrule station. Once you establish the correct depth you can
finish all of your butt strips.
From our experience the most difficult areas to cut are the nodes because of crookedness and hardness.
The Magic Star Cutter will follow some nodes even though they are not perfectly straight and hollow
them well. However, if you are having trouble with it cutting slightly off center then restraighten your
nodes.
When you get through hollowing you may have some splinters of bamboo along the cuts. You can
gently remove them by hand or with the brass brush included with the cutter by brushing them off while
the strip is attached to your anvil. Another method is to tape the sections together for gluing and brush
them off with the brass brush. You need to make sure that there are no bamboo splinters left that could
interfere with a good glue seam.
As with all strip cutting you need to remove the “fuzz” from the top of your strips after planing and
before gluing. Do this carefully so as to remove just the “fuzz” or you will end up with a hole or void
in the center of the star.
When gluing spread the glue in your normal way. Then take your glue brush and wipe it along the
hollow sections wiping out as much excess glue as you can while still leaving adequate glue for good
adhesion. When gluing butts it’s essential to start binding them at the tip where the butt is solid and
bind towards the bottom otherwise they won’t glue straight.
Star Hollowing Tip Strips
Tips are easier to hollow because the tip taper drops away from the Magic Star Cutter as you progress
up the strip. As on the butts you must use the extension hold down shoe in order to have the correct
angle to properly hold the strip centered on the cutter.
Before you can cut the tip splines you must remove the butt-finishing anvil and install the tip-finishing
anvil without any shims. This is necessary in order for the correct hold down shoe to fit over the anvil
and hold down the narrow tip strips. Then if you want your wall thickness to be constant set your tip
anvil with no taper using your dial indicator. Here again I suggest setting the adjustable bed .010”
above the base. Once you have the anvil level proceed to the next step.
Mount your tip spline on your anvil with the tip just short of the end of the anvil. Determine where the
ferrule station will be on your tip and make a pencil mark at that point. Move up the tip spline 2” and
make another mark. This will be where your cutting begins. Mark your tip anvil at this point with a
felt tip pen. Mount your plane on the base with the Magic Star Cutter over the tip mark to see if there
is a plane stop near the end of the plane. If there is you can mount the plane stop otherwise I suggest
that you put a temporary stop using a “C” clamp so you can start cutting exactly at the anvil mark.
6 (Magic Star Cutter)
Setting up the tip cutting is opposite from the butt. On the butt you dropped the butt spline away from
the cutter in the ferrule area whereas with the tips you would generally keep the wall thickness even so
there is no taper. Naturally, you could taper the wall thickness but probably wouldn’t want to except,
perhaps, on large rods such as spey tapers.
Set the Hand Mill plane on the base with the carbide cutters over the bamboo spline where will start
cutting making sure the cutter is above the bamboo. Adjust the cutter until it just touches the bamboo.
Remove the plane and adjust the cutter down .006” to .008” and take your first cut. You want to
move down the strip at a slow to moderate speed. As soon as the cutter is no longer cutting remove
the plane. Making cuts of .005”-.007” should be satisfactory. You can determine the wall thickness
as mentioned in the butt hollowing section above. The cutting of the tip will go quickly because you
are not removing much material. The hollowing should begin about 2” from the ferrule station and
gradually taper out to no hollow at all part way up the strip. Once the first tip is finished satisfactorily
you can finish hollowing all of the tips.
I can’t give an estimate of the life of the carbide inserts. Since the inserts are C-2 carbide they are hard
and wear resistant and should hollow many strips. The triangle inserts have three cutting edges whereas
the square cutters have four. As with other inserts you can keep track of the edges that have been used
by marking on the back with a felt tip pen. Because there is a small area of bamboo actually being cut
you will not notice a significant increase in the effort required to push a dull cutter through the bamboo.
As with the regular carbide inserts when they start getting too dull they will not cut cleanly.
In order to provide openness about the carbide inserts I am providing their specifications so users may
find their own supplier. The carbide inserts have an IC (inscribed radius) of 1/4”. The carbide grade is
C-2. Their ANSI designation for the square inserts is SPGW222J and the triangle inserts is TPGW222J.
Both have a tip radius of 1/32” with an IC of +/-.001” on the cutting edge with a thickness tolerance
of +/-.005”.
The thickness tolerance in this application isn’t critical because the pocket is deeper than any insert
and the IC achieves the location. This insert also has a recessed hole.
To recap the carbide insert information I had to have them custom ground to get the specific tip radius
and tolerance specifications that I wanted. The specific inserts that I am supplying may not be available
except through me.
I purchase them from the following company:
Wit-son Carbide Tool, Inc.
6490 Rogers Bridge Road
East Jordan, MI 49727
Telephone: (231) 536-2247
Email: [email protected] 7 (Magic Star Cutter)
Revised May 2007