Scored mold top at sprue plate pivot point

[kevin c]

This keeps happening to my 8 cavity aluminum MP molds. The scoring is in a circular pattern with the pivot bolt being at the center, and I think that there may be burrs raising the plate a bit (I can see light between the plate and mold blocks), causing fins on the boolit bases. I'd like suggestions from more experienced casters on what to do to repair the damage, and how to prevent it from happening again.

Maybe it'd help to describe the mold and how I cast: The pot is PID controlled at 720° and I take care to let the sprue harden up prior to cutting. Roughly two fills per minute, per mold, whether I use one or two alternating. The mold top and the plate underside are pretreated, and during casting, periodically retreated, with a rubdown using a 2 stroke oiled rag that helps remove lead build up (though there's still build up on the underside of the plate around the sprue holes - that's another thread). The sprue bolt tension is maintained by a wave washer (there's also a wave washer on the stop bolt) and the bolt is turned in enough so the the plate and its handle don't quite open by themselves when the blocks are rotated handle side down. There is also a set screw for the bolt so that it doesn't turn, for which I filed a flat into the bolt threads to set the position. This mold has a cammed sprue plate cutter. Prior to first use I disassembled the mold and oiled the bolt and the area of concern between the block top and plate before reassembly, but haven't disassembled the molds since.

Can I get rid of the scoring by refinishing the top of the blocks, and how can I do that if I don't have access to a mill?

What might I be doing that causes the scoring? Is it lack of lubrication? Is it torquing by pulling on the cam lever at a bad angle or too late? Could letting the plate remain rotated out a full 180° from its closed position while vigorously tapping on the mold handle hinge be too much leverage (it's a thick, heavy plate, and from pivot to the end of the cam lever is a full 10".

I confess that I've damaged four molds this way. I've got a new one on order but this is an expensive habit I'd like to break before I start using #5.

Thanks in advance,

Kevin c

[Conditor22]

The cause is sinching the sprue plate down too tight and not lubing the sprue plate screw/pivot point regularly.

You can salvage this with a little work on your part.

What I did when a Got a used mold in this condition-- I got out a 12x12 piece of glass and a sheet of 400 wet-dry sandpaper, take off the sprue plate, remove the sprue plate stop and remove the handles. set the mold on the sandpaper and with even pressure and sand the top of the mold until everything is even (you will not remove all the circular groves) then sand the bottom of the sprue plate. Try the plate on the mold and see if you can still see daylight between it. If not switch to 600 grit and smooth what you sanded.

[I have several molds where the sprue plate swings freely but still lays flat on the top of the mold not getting any flashing]

IF the mold doesn't have a wave washer, install one between the top of the sprue plate and the bolt. Don't overtighten

Get a needle dropper and put 1 or 2 micro drips of synthetic 2 stroke gas additive on the sprue plate screw and work the sprue plate open and closed.

If you see ANY oil on the top of the mold wipe it off with a paper towel. --- my 2¢

[Wally]

Conditor22 Has offered great advice...at a reasonable cost! . When you cast again, as soon as you see leak smears on the sprue plate, wipe off with an old oily rag. It will remove the lead streaks and prevent it from happening for a few cast cycles. The cause is from the sprue plate being too hot.

[kevin c]

Thank you, gentlemen! The wisdom, experience and advice is much appreciated.