Bent Sprue Plate

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  • Last Post 05 December 2022
chopperman posted this 04 December 2022

 I came across a 10 cavity mold and cavities are in great shape,but it has a couple of problems. The first one is a badly boogered handle screw in one half of the mold, not too big a problem for me. The other is a bent sprue plate. It has a space of about a 32nd inch at the handle end and tapers to about the middle length. Would heating it up and trying to bend it straight in a vice be a logical way to do this or leave it alone. I haven't tried this mold yet so maybe finish the cleanup then cast some first.

 Thanks for any help

Stan Sorokowski

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Bud Hyett posted this 04 December 2022

Is the .032 gap measured with sprue plate screwed to the mold or simply sitting on the mold? Overtightening can cause the far end to rise. Is the gap even across the mold face or higher on one side? You may have bi-dimensional warpage. This can mean severe rework. 

I'd measure the thickness to see if there is enough metal to grind the base flat, Take it to a local machine shop (or a very good amateur machinist) to have their analysis to see if they concur. They can heat it to straighten close to flat, then surface grind the top to get enough surface for flatness, flip and get 100% cleanup on the bottom. 

This will also give you fresh sharp cutting edges on the sprue holes.

Farm boy from Illinois, living in the magical Pacific Northwest

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358156hp posted this 04 December 2022

I'm concerned that trying to straighten the plate will be futile once the plate is heated again. I completely agree with Bud on the course of action. In addition, the shop may be able to shot peen the plate before surfacing to help "stress relieve" the bent metal and  prevent the bend from potentially returning. A smaller automotive machine shop should be able to handle the job just fine, you don't need a really big machine shop for a job like this. Talk to the machinist and tell him what you need. They will want to see the plate in person.

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chopperman posted this 05 December 2022

 When I tighten the sprue hinge screw firm but are able to open the sprue plate I have about .032" on the handle end. When I tighten the sprue plate lock screw firmly I have .017" on the handle end and on the lock screw side .005", so there is a little twist. But the sprue plate is harder to open fully.I think this mold was abused by someone not accustomed to a large 10 cavity mold. The bottom of the sprue plate has many dents like they couldn't get their bullets to drop, no marks on the handles hinge bolts at all. The striking handle of the sprue plate was not opened with a wooden stick, but hammered with a metal pipe or hammer and deformed its side.

 I think it will have a machinist square it up and flatten it proper after shot peening to normalize the metal. If the cavities weren't in good shape or the halves didn't line up nicely, I'd part it out. I bought it so low I have a lot of leeway to spend a little money on it

Stan Sorokowski

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porthos posted this 05 December 2022

it can be straightned with  a hammer (copper  or brass), straight edge, files and emery paper. years ago it seemed popular to make spru plates out of aluminum. i've made several; but id dosen't seem popular today.

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