Mold Backcast for 3/4" x 8 3/4" blanks

[rherrell]

I made this for a well known pen company, he called it a "mold backcast" so I'll take his word for it.

The shell is 24ga. galvinized steel.

The rods are W-1 Tool Steel, the same material that my toolrests are made from, polished to 800 grit.

The base is 3/4" Delrin.

I had fun making it, I love doing something different.

Here are some pics, I hope you enjoy!

 

[duncsuss]

Am I right in guessing it's a "master form" that he'll use to make blank molds for vertical casting? I've seen two-part silicone mixtures for sale but hadn't figured out how to get the cylindrical holes - my gut told me that wooden dowels were not going to be easy to remove, polished steel should be much better

 

[rherrell]

Yes, I also thought it was a "master" but he called it a backcast.

The sides stick up 1/2" above the rods, that will become the base when you remove it and turn it upside down. It's filled with silicon rubber.

 

[egnald]

Very Cool! - In a foundry usually the term "backcast" refers to the process and not the mold itself. I'm guessing that it was called a backcast because backcasting is the process that the tooling will be used in. Essentially backcasting is the pouring of a material into a mold -- the empty void between the pattern, (the cores i.e. the matrix of rods in this case) and an outer shell or container. Regardless of what it is called, it is a very cool piece of tooling! - kind of a mold mold! - Dave

PS I was sure rooting for the Tar Heels in the finals at the Men's College World Series and had high hopes after they beat Oklahoma in the second game of the finals. This was the 13th time they made it to Omaha and the 3rd time they have finished as runner-up. I'm sure that in true relentless, Tar Heel fashion, they are going to become national champs some day!