Appreciation post: The old guy at the Pittsburgh foundry show who showed me his riser trick

I was at the Pittsburgh foundry show last fall and got talking to this retired pattern maker. He saw me looking at a casting with some shrinkage and asked if I used a double riser. I told him no, I just used one big one. He took a piece of chalk and drew on the floor how he puts a smaller riser right next to the main one on heavy sections. Tried it on a 200-pound gear blank pour last week and the sound changed when it fed, no shrinkage at all. Has anyone else used this setup for thick castings?

4 comments

4 Comments

parkernelson19h ago

Yeah I read somewhere that old pattern makers had all these weird tricks they'd never write down, just passed them along at shows like that. Makes sense though, putting a smaller riser next to a big one lets the big one feed while the small one chills faster and keeps the heat localized. Never tried it myself but your gear blank story has me thinking about it now.

paige_harris1mo ago

What's the spacing between the two risers?

max9631mo ago

Have you checked if your local building code has a rule for this? Mine says the gap can't let a four inch sphere pass through, which is a safety thing for little kids. That means your risers need to be less than four inches apart. A lot of people just guess, but getting it wrong could be a real problem later. You should look up the exact number for your area before you build anything.

ramirez.caleb19h ago

Ngl that caught me off guard. Why would a building code even have a say in how far apart your risers are, that seems wild.