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I finally figured out why my cope and drag seals were always blowing out
Been using the same gating setup for years on our old Hunter 20, but we'd get a bad blow maybe one in five pours. My kid was watching me ram up a flask last week and just said, 'Dad, why is the sand so much darker there?' He pointed right where the runner met the sprue. I was packing it way too tight, creating a hard spot that couldn't vent. Switched to a lighter touch on that spot and ran 50 molds this week with zero defects. Anyone else have a simple fix that took way too long to see?
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jake_martin162mo ago
Switching to a softer ram around the gates fixed my blowouts too, didn't it?
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skyler_white952mo ago
Glad you fixed your blow problem, but calling it a venting issue isn't quite right. That hard spot acts like a chill, cooling the metal too fast and building pressure. The lighter pack lets the sand give a little, absorbing the shock instead of trying to let gas out. It's a strength thing, not a porosity thing.
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betty_reed612mo ago
Actually skyler's got a point about the pressure. That hard sand doesn't just block gas, it makes a wall the metal can't push past. So it finds the weak spot and blows.
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