Start of the furnace build" Molds aka Forms

Gathering the Material
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Been scouting.

The burner will be a burnzOmatic torch with a steel pipe to feed into the furnace.   Maybe introduce a bit more air between the existing torch and the furnace.

I have a 2" OD metal water pipe to use for small crucibles.  If I use a 4" schedule 40 PVC pipe for the core this gives an inch on each side which should be more then plenty for the 2" crucible.  Maybe a 3" or 3 1/2" might work.  Slice it into 4 staves then tape it back together around a set of wood discs.

It would be nice if I could fins a 6" ID sono tube but that will not happen.   I do have an 8" ID schedule 40 PVC pipe that I can cut into staves and reassemble inside wood rings.  The OD of the 4" is 4.5" and the ID of the 8" is 8" a difference of 3 1/2".  So the walls will be 1.75".  A bit on the thick side but I can live with it or create a larger Styrofoam core to replace the 4" PCV.

Building the Mold/Form
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The refractory core.  AKA the form for the inside of the refractory cylinder.  The pipe is being sectioned so the two narrow sides can be easily removed.

Created a 12" section with square ends with the chop saw.











Replaced the table saw cross cut blade with a plywood or rip blade with a narrower kerf.  The less removed the rounder it will be when reassembled.











First cut was easy as it only needed to be straight.


Second cut. I wanted the cuts on each side to be in the same plane.    The blade of this adjustable angle tool (Square) fit nicely in the previous cut.  That allowed me to align the flat bottom of the tool to the table saw bed knowing the blade was 90 degrees.

Third cut.  Aligned the existing cuts with the speed square.  This ensures the next cut will be parallel to the 2 previous cuts.

Forth cut. There was no good way to align the last cut.  I used the first narrow sections as an alignment guide to estimate where it should go.

The  four staves.  Tape or string will hold them together around two or three wood disks.  The edges on the smaller staves have no draft so they can be pulled away from the inside of the refractory.  This will release the larger staves.











The outside form for the refractory cylinder is cut from 8" schedule 40 PVC.

Neither end of the pipe was cut straight.















This was to big to easily fit into the miter saw.   I made a cut, rotated the pipe using the saw blade in the existing kerf as a guide, and made another cut.  Several cuts later it was finished.   Not perfect but close enough that I can sand the ends flat.

figuring