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Gene Larson's Shop Notes |
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YOUR OWN LUMBER MILL
FOR SHIP MODEL BUILDERS
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By: Eugene L. Larson Reproduced here in its original form and content but with minor changes for significant differences due to progress over the years. First published in Ships in Scale Magazine, July/August 1987.
The purpose of this article is to present
some thoughts on processing woods from bulk pieces acquired at lumberyards,
specialty wood sources, the forest, or orchard. Many comments made here are
based upon my association with the Nautical Research Guild (NRG), Washington
Ship Model Society (WSMS), and model builders I've met in general. I
especially want to thank Ken Dorr for his help in compiling the list of woods
(coming in Part Two) and sharing his techniques in processing lumber. Neither
the ideas nor the list is intended to be all inclusive. If anyone has
additions, corrections, or comments, I'd appreciate a letter. A future update
to this article is then possible if enough material is collected. A common question is how to obtain the
properly dimensioned woods required for a model. A few years ago before I had
acquired a caliper, I bought some 1/32" (0.8mm) sheet walnut from a
hobby shop to make gratings. All the notches were carefully cut on a small table
saw with a 0.032 blade. Then came the assembly. I
was shocked when the strips wouldn't fit in the notches. I obtained a dial
caliper and discovered that the 1/32" wood which had been checked with a
ruler wasn't 0.031, but 0.042 - more than enough to prevent assembly. In some
cases variations of 0.010 aren't critical, in others like this, it's
essential to have a closer tolerance. So how is wood processed to dimensions
within 0.003 to 0.005? If a few short pieces are needed, a sanding
block and arm power will provide the necessary stock. Some wood may be wasted
by sanding too much, but it isn't a great loss. However, the requirement to
process a large quantity of special wood such as apple, pear, holly, maple,
or the more exotic types presents a significant problem. All the solutions
I've tried or been exposed to have advantages and disadvantages. I'll try to
cover these with the purpose of letting you decide how to go. I don't wish to
endorse any product and especially not to criticize them. SAWS There are several miniature saws on the
market which are good for thin cuts and short pieces. Generally, the motor is
small (1/12 hp) which causes stalling on thicker cuts. Also, the bearings
holding the blade mandrel are usually loose. This results in an intolerable
play in the blade when cutting. The thinner blades furnished with the
machines don't have a set to them. Thus cuts are limited to 1/4" (6.5mm)
thickness or less, depending on the hardness of the wood, or burning occurs.
Other thin blades can be purchased from companies such as Thurston, and are
available in a variety of thicknesses. However, they are designed for metal
slotting and slitting, and don't have any set to their teeth. The 100-tooth Dremel
4" blade does have set and will do a decent job on thicker cuts if there
is no bearing play and the motor doesn't stall. A new miniature saw
advertised by Preac Tool Company is represented as
having solved the problems noted above. The advertisement states that the
high-quality blade produces a cut so smooth that sanding isn't required. It
comes with a 4" x 6' table and is quite expensive ($300.00 range). I
haven't tried the saw, so can't comment further. (I since have acquired the
saw and it does in fact perform well. Micro-Mark also offers a saw with carbide
tip blade option.) Whether I use a 10" table, radial arm,
or 2" miniature, I can't consistently saw long planks without getting
teeth marks and slight thickness variations. It's difficult to hold the wood
to the fence throughout the cut, and after a few passes, the blade will dull
just enough to prevent the ultra-smooth surface, especially when working with
harder woods like cherry, maple, and walnut. Jack Kitzerow of
the NRG and Nautical Research and Model Ship Society, Chicago, has designed a
miniature circular saw table which utilizes any motor from 1/15 to 1/4 hp.
The larger motor avoids the stalling problem and the bearing arrangement
eliminates play in the shaft. A much smoother cut is produced as long as the
appropriate blade is used. However, the disadvantage is that a metal lathe is
required to make some of the parts. Details of this saw have been printed in
The Fife Rail, a copyright publication of the I've cut wood rather accurately on a 10'
saw table with a carbide-tipped blade. As mentioned earlier, the tolerance
may not be enough for the project. Also, it isn't always cost effective to
waste more wood than is produced. The saw cut is over 1/8" (3mm) which
is twice as much sawdust as is saved when cutting 1/16" (1.5mm) planks.
Wastage should not be a prime concern, since most modeling projects don't
require so much wood that even 200% waste would be a major cost factor. When using any saw, the best method I've
found is to cut the thicker dimension first, then slice off the desired
planks. This gives more control of the wood and, therefore, the cut (Figure 1).
The initial stock should be planed smooth and square on at least two
adjoining sides. This can be done by the lumberyard or specified when
ordering through the mail. Otherwise, a jointer and perhaps a planer are
necessary to do the job - no small expense, and only justified if you're
really into production or have other woodworking needs.
DISC SANDING During the construction of a large kit model
which I was drastically modifying to achieve greater accuracy, I discovered
the walnut planks were of very poor quality. They were cut on a bias, not
with the grain, and every attempt to bend them resulted in splitting and
breaking. I purchased some high quality, close - and straight - grained
walnut and cut 3/4" x 3/16+" (19 x 5mm) slabs on my table saw. A Sears sanding disc which has a 2 degree bevel on one side
and flat on the other was purchased and placed on my Shopsmith.
I used the beveled side to sand the slabs to their final 3/16"
dimensions by running the wood through a fence arrangement next to the
sanding disc. The bevel provides a single point of contact for the sanding.
Tilt the table and fence 2 degrees relative to the disc to make the fence
face parallel to the disc at the sanding point. Use the top portion of the
disc so the sanding is nearly parallel to the direction travel of the wood
(Figure 2).
Disadvantages are that only a small portion
of the disc does the sanding resulting in uneven wear, and thin strips can
fall into the slot between the disc and table. Also, this is a very awkward
arrangement and several lengths of wood were wasted trying to get a smooth
finish. It was difficult to hold the wood against the fence to avoid
chattering due to the disc's large size. The amount of dust produced was incredible,
and a shop vac hose held near the sanding didn't
help much. However, the required planks were eventually produced. The 3/4' x
1/16" slabs were then sliced on a miniature saw to 1/16" X 3/16'
size. These were not sanded, since the cuts on the 3/16" surface would
be sanded away later by hand on the model. This isn't always possible. DRUM THICKNESS SANDER Another method to process planks is to
rough cut them on a band saw, table saw, or radial arm saw, and then use a
drum thickness sander to obtain the finished surface. The band saw produces
the least waste in the cut and is one of the more common tools in a home
workshop. There are large, commercial thickness sanders on the market which
run up to $1,500.00. This is usually out of our price range. For several
years, I offered plans and instructions for a model builder's drum thickness
sander, and was finally pressured into producing a completed unit. It's
available through the Model Ship Marina (No longer available. Preac design is a follow-on, but with a less powerful
motor.) The sander (was) expensive due to its metal construction, large motor, and specially machined parts.
A disadvantage of thickness sanders is the
amount of dust they produce. A shop vac is
essential. A home vacuum isn't recommended, since the bag clogs very quickly
with the fine dust. Also, a dial caliper is essential to check the thickness
for any given setup, since the machine can not be calibrated to the
tolerances required due to variations in and wear of the sandpaper. The end
product can be held to tolerances of 0.004 or less. A thickness of 0.005 or
less (thickness of this page) can be achieved if the wood grain structure
will permit it. Consideration must be given to the type of
sand- paper on the sanding drum. I try to avoid the slotted drum where the
sheet must be wrapped around it, the ends inserted into the slot, and
secured. This works well while the paper is tight, but with use it stretches
and the resulting poor fit affects the sanding. Plans for my earlier homemade sander called
for gluing the paper onto the drum. This works fine until it's time to
replace the paper. Regardless of the adhesive, there is always a mess. The
least messy is the glue produced for holding the sheets of paper to the flat
discs used in auto body work. There is also a solvent available. Check the
local auto paint store. A removable sleeve is best, but in this case the
width is limited to 3" (76mm). It should accommodate most projects. (A
later design of my sander pictured here used a new-to-the-market 6" long
drum). My sander is based upon a rotating drum
over an adjustable flat plate table. This design is several steps of
refinement (hopefully) on a unit used and demonstrated by Marvin Bryant of
the Hampton Roads Ship Model Society. Ken Dorr and I built several similar
units and changed them to their present configuration (see photo). To use it
and similar sanders, slabs are again sliced off the large stock to the
thicker dimension. These pieces are sanded, the thinner dimension is cut, and
then this face is sanded. Since I have the machinery for my half hull kit
business, I use a band saw to cut the wood to approximately 1/32"
(0.8mm) oversize, After each cut, I pass the original large stock through a
jointer to obtain a smooth surface. This isn't necessary, only convenient.
For band saw cuts on both faces, just make the strips thicker to accommodate
the extra sanding. With a band saw, it's easier to cut the wood straight if a
fence or pivot block is used (Figure 3).
The sander controls the thickness of the
wood by a positive-action adjusting mechanism. The final dimension is
achieved by running the wood through the sander a few times, adjusting the
thickness accordingly. Several thin sanding passes are better than a single
deep one. If more than one piece is to be dimensioned, run all through the
sander before a thickness adjustment is made. This achieves a very accurate
consistency. A continuous push through the sander is
essential, since any stopping will produce a "dip" in the wood. On
all sanders, a push stick is necessary when handling short pieces, and some
kind of guard should be incorporated to prevent sanded fingers and/or
throwback. Always push the wood against the rotation of the sanding disc or
drum, or the machine will pull the wood from your hands and hurl it like a
missile. A thickness sander does more than just make
planks. After a grating is assembled, it's usually necessary to sand it flat.
If you've tried to do this with a sheet of sandpaper on a flat surface or
using a sanding block, you probably have achieved a smooth top, but rounded
edges. By building a simple sliding jig to hold the grating and making very
light passes, the grating can be sanded flat without chipping the
"teeth" (Figure 4).
Another use for thickness sanders is for
the production of multi-wood rudders. For my finished half hulls, I assemble
three 3/32" (2.4mm) pieces of wood; usually cherry, maple (waterline),
and walnut. When the glue is dry, I pass the assembly through the sander to
obtain a 1/16" (1.5mm) dimension. A push stick is essential! The rudder
is then cut to shape (Figure 5).
Away from modeling, this method works well
for finishing inlays and parquetry, as well as making the initial stock for
this work. When the project is assembled and dry, lightly pass it through the
sander, especially for thin inlays. The surface comes out flat without
rounded corners. A secondary advantage is that any glue accidentally smeared
on the face is removed. The sander can also produce edge veneers from special
woods for finishing plywood projects. In case you have planks already cut and did
not do the thicker dimension first, the edges can still be sanded smooth with
another sliding jig (Figure 6).
Very thin sanding can be accomplished by gluing
the leading tip of the piece to be sanded to a sliding jig which has been
sanded flat. It's impossible to push very thin stock through the sander
without buckling it. By gluing the wood to the jig, the result is a pull
instead of a push (Figure 7). I've sanded walnut to as thin as 0.005. After
that it disappears!
The advantages of a thickness sander are:
1) the ability to consistently produce accurately dimensioned material to any
length, 2) the variety of woods that become practical, and 3) its many
associated uses. The disadvantages are: 1) the cost or effort to build one,
2) dust produced, and 3) the support equipment necessary or desirable;
vacuum, band saw, and jointer (helpful). In the next part, I'll provide a list of
woods, their characteristics and their applicability to model building. BIBLIOGRAPHY A
Ship Modelmaker's Manual, John Bowen, Conway
Maritime Press Ltd., Chrysalis Books, 9 Blenheim Court, Brewery Road, London,
N7 9NT. Nautical
Research Journal, Nautical Research Guild, Scale
ModelSailing Ships, John Bowen, Ship
Modelling Hints & Tips, J.H. Craine, Ship
Modeler's Shop Notes, Nautical Research Guild. The
Fife Rail, Nautical Research and Model Ship Society, The
Main Wale, Wood
Magazine, Better Homes and Gardens, ADDRESSES Nautical
Research and Model Ship Society, Preac Tool
Co., Inc., 1596 Pea Pond Road, North Bellmore, NY 11710-2926, 516-333-1500. Thurston
Manufacturing Company, |
