The OSHA reg from 1985 that changed my mind on old vs new molds

I was digging through old safety manuals in the break room and found a 1985 OSHA notice about sprue sizes. It said the average iron foundry back then ran sprues at 1.5 inches for a 200 pound pour. We run the same job today with 0.75 inch sprues and get better yield every time. That got me thinking, are we over-engineering our gating systems now or were they just playing it safe? I've got old timers saying bigger is better for turbulence, but the numbers say otherwise. Anyone else seen old specs that just don't hold up against modern practice?

2 comments

2 Comments

adam1861d ago

Actually that 1985 spec might be about more than just playing it safe. Sprue sizes back then were often set for hand pouring with less controlled ladle height, so bigger sprues gave you more room for error. Modern pouring controls and refractory coatings changed the game, so comparing them straight up misses why those numbers existed in the first place. The old timers have a point about turbulence, but they're fighting a problem that newer pouring methods mostly solved. Curious what your pour setup looks like now, cause that changes the calculation a lot.

danielk841d ago

My number two crucible is a ten pounder and I still get a 12% shrink rate on A356 even with a bottom pour and a stopper rod, so I'm not buying that turbulence is a solved problem. @adam186, you're assuming everyone runs a modern rig, but half the guys on this board are still using a bent rod and a steel ladle, and that 1985 spec takes their mess into account. Those bigger sprues also give you a better chance of feeding a cold mold when the pour stalls, which happens way more than people admit. Newer coatings help, sure, but they don't fix a shaky hand or a bad gate placement, and that's where the old numbers still earn their keep.