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Molding Heater Knobs
By Jeff Stotlar 1942 Chevy 1/2-Ton Pickup "stotman" Bolter # 19717 Newbury, Ohio		July 2009

Making your own small, plastic parts

When I was restoring old arcade games, I often had to make my own parts. Recently I needed to get some knobs for my heater. They currently are not available so I decided to make my own. The materials required for this are fairly expensive, so if knobs are available, you should probably buy them. However, if you cannot find them this is a great way to go.

This part required a two piece mold due to the shape of the part. If the knob had been flat on one side, I could have just put the part flat side down, built a lego box around it and poured the rubber over it.

All of the materials I used came from Alumilite. The starter kit runs around $70.00.

<< Click on images for larger view >>

Step One: make a mold for your project

Here, I have made a partial mold box out of legos. For this part the mold does not have to be very big. I have filled the box with clay.

Step Two: fill part to be cast with clay

Here, I have filled in the hollow part of the piece with clay as it can be solid on the new part.

Step Three: bury parts half way in clay

Note I have added a plastic piece. This will later become a pour hole for the resin.

Step Four: make clean clay lines at the edge of the piece

The cleaner the edge where the clay meets the edge of the piece the less work you will have later cleaning up the mold line.

Step Five: fill the lego box with silicone rubber

Step Six: flip the box over and remove the clay


Step Seven: apply mold release		Step Eight: pour the other half of the mold		Step Nine: remove Legos and original part

Step Ten: tape the mold together and pour resin

Note, I have enlarged the pour hole. I also added two vents to allow air to escape as I pour the resin.

Step Eleven: demold part

Lightly sand the new part and paint any color you wish.

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