MAKING A MOLD
The process of making a mold is actually relatively easy.
I start with a very carefully made half template made of 3/4" baltic
birch plywood ( a very high grade of plywood - which has no voids).
The
shape of the new mold is first drawn/traced on to a nice clean piece of
poster board and then traced onto a piece of baltic birch plywood (a
high grade of ply with no voids).
the
shape is carefully cut on the bandsaw - slightly proud of the final
line. This is then sanded with a drum sander to the exact line
with smooth fair curves.
Then it is
simply a matter of using a piloted cutter in a router (or here - in the
router collet of my shaper) to duplicate this shape. I use double
stick tape to duplicate the original for the "other half" of
the guitar outline, and then I start gluing up layers (and trimming each
layer as I go) until I reach the desired thickness. This one (which
will be an "assembly" mold for my parlor shape) will be 2 1/4
inches thick.
Another view of the trimming process.
Another
view of the router bit cutting a new layer to the shape of the earlier
layers.
The next step is to hold the two halves of the mold together.
I used to use mending plates screwed into the top and bottom surfaces.
This works better. It is a toggle clamp (available in many of the
current woodworking catalogs) which draws the two halves together.
It is adjustable for a tight fit. The dowel which spans the joint
between the two halves, and is glued into one half) serves to ensure that
the two halves are in perfect registration. This works really well.
The next
step is to make the spreaders which are used to hold the ribs firmly and
accurately in the mold. I use threaded wooden dowels to do
this. The threaded dowels are made with a jig which is made by
BEALE, and can be found is several of the woodworking tool catalogs.
this works quite well. The next several photos show how this is
done. This photo shows the jig used to thread the dowel.
This is
the threaded dowel and the tap used to thread the spreader block (only one
gets threaded.)
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website and all of its content, text and images are copyright ©1997-2011
by Charles A. Hoffman. All rights reserved.
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