prs
12-13-2013, 01:01 PM
This is a Lee 6 cavity for the bb 452-200-SWC (traditional lube 68 clone). When spanky new last summer it was a bit stubborn to wash-up and very reluctant to drop flawless castings. I had done my usual routine of beveling the edge of the spru plate and slightly breaking the edge of the mold blocks where they meet under the spru plate, and making sure the spru plate pivot was not too tight. Still it seemed to have trouble venting quick enough and I would get too many culls with those funny worm-wood or scarab beetle "etchings" on them.
Took note of the advice here to try Comet, and did so. Worked maybe a little better, but still too many of those same type rejects. Actually, the flaw patterns were/are so shallow that running through the 452 H&G dies erased them from the drive bands. Still, I don't like them. So, I took a sharp awl and a square and made a groove midway between each cavity of one block and another just above the metplat of the cavities. That seemed to work pretty well, but the dang thing still wanted to be run hot and with hot alloy (750F on my PID). Then after a few sessions it was "wanting" more mold heat to drop pretty and now in order to drop them pretty the mold needs to be so hot that the castings are stubborn to drop from the mold. If I run it cooler, the worm-wood patterns return on a good number of the boolits. Filling (bottom pour) slower seems to help and my typical pattern of filling just off center of the sprue plate opening seems to help, but swirling the fill makes it worse. Of course, the heat and slow pour really slows my pace and that, as well as 10 to 20% culls negates the advantage of a 6 cavity mold over the iron 4 cavity. I am still thinking its the air having trouble getting out fast enough, maybe that blasted bb design. I am considering Leementing the cavities with Mutters' Billet Aluminum polish even though my alloy (95pb:2sn:3sb) is dropping boolits at .453+" in each cavity. I am also considering reaming out the bb of each cavity, but rather not have to resort to such.
Oh, nearly forgot, it occurred to me after that last session that this and another stubborn mold are the only aluminum molds whith which I have used Stihl synthetic 2 cycle oil as the pin and pivot lube. I reckon maybe another scrub with comet and casting without lube or with NRA 50:50 (what I have always used before) may be in order before Leementing or reaming out the bb. I notice Lee is now recommending anti-sieve paste.
Any other bright ideas? How about using it as a paper weight?
prs
Took note of the advice here to try Comet, and did so. Worked maybe a little better, but still too many of those same type rejects. Actually, the flaw patterns were/are so shallow that running through the 452 H&G dies erased them from the drive bands. Still, I don't like them. So, I took a sharp awl and a square and made a groove midway between each cavity of one block and another just above the metplat of the cavities. That seemed to work pretty well, but the dang thing still wanted to be run hot and with hot alloy (750F on my PID). Then after a few sessions it was "wanting" more mold heat to drop pretty and now in order to drop them pretty the mold needs to be so hot that the castings are stubborn to drop from the mold. If I run it cooler, the worm-wood patterns return on a good number of the boolits. Filling (bottom pour) slower seems to help and my typical pattern of filling just off center of the sprue plate opening seems to help, but swirling the fill makes it worse. Of course, the heat and slow pour really slows my pace and that, as well as 10 to 20% culls negates the advantage of a 6 cavity mold over the iron 4 cavity. I am still thinking its the air having trouble getting out fast enough, maybe that blasted bb design. I am considering Leementing the cavities with Mutters' Billet Aluminum polish even though my alloy (95pb:2sn:3sb) is dropping boolits at .453+" in each cavity. I am also considering reaming out the bb of each cavity, but rather not have to resort to such.
Oh, nearly forgot, it occurred to me after that last session that this and another stubborn mold are the only aluminum molds whith which I have used Stihl synthetic 2 cycle oil as the pin and pivot lube. I reckon maybe another scrub with comet and casting without lube or with NRA 50:50 (what I have always used before) may be in order before Leementing or reaming out the bb. I notice Lee is now recommending anti-sieve paste.
Any other bright ideas? How about using it as a paper weight?
prs