The online magazine on the history and operation of vintage scale model trains in American OO gauge

Tuesday, June 6, 2017

Castings! Part I, making the molds

Going way back to my roots in American OO, when I was in high school I was making molds and castings with the help of Temple Nieter, described further in this article. Between then and 2008 I had hardly made any new castings in the molds (and all were metal castings as well, I had never had luck with casting resins), and I had not had the inclination to make any new molds either.

But then a project comes along and inspires you a bit, and in my case, it was the acquisition of one almost complete Nason sand cast aluminum boxcar and three key parts of another. I at the least wanted to try to duplicate the missing pieces for the second car and who knows, maybe I could duplicate the entire car?

After considering options I decided to order the resin casting starter set that Micro-Mark sells, and it does have all you need to get started.

To make the molds I used the same methods Temple taught me with really no big tweaks, mostly illustrated in the photos with this article. First step is to put a layer of the clay material (it is not actually clay, it won’t dry out) down (I put it on a piece of metal) and roll it flat. Put the part on it and put it half way down into the clay. You will need to make fences from metal (using clips to keep it closed) and also use a screwdriver or punch to put holes in the clay to serve as keys for the other half of the mold.

They supply a mold release that you brush on, it worked well. Years ago, I found mold release to be a big issue, the one supplied by the maker I used then did not work. I ended up using spray wax which was a solution but not a great one. The liquid supplied by Micro-Mark works.

Then you pour the first half. When the mold material has cured you pull the mold up and invert it. Put up the fences again, apply plenty of mold release again, and pour the second half. And with that you will soon have a two-part mold of your part.

When you have the mold halves separated cut in the needed vents and fill holes with a hobby knife.

In part II we will look at my initial attempts to make resin castings.

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