Originally Posted by
uscra112
Inadequate fillout in one cavity is usually caused by the mould and especially the cutoff plate not being hot enough. One reason I don't use a bottom-pour pot anymore is that it's a pain to spill enough molten lead over the cutoff plate to keep it hot, and to fill the dimples in the plate. Not filling the dimples is probably why you're getting those "boogers". The sprue plate dimples are not only full but with a nice bubble of liquid lead on top to fully harden before cutting off the sprue. The lead is so hot (highest setting on the pot) that it takes about 10 seconds for the sprue to fully crinkle up and change color, indicating it is finally solid. Still, on or the other cavity will many times not have a perfect base to the boolit, but a ever so slightly rounded base. On the PB side this won't do. On the GC side the rest of the boolit is perfect and I will let the GC take care of that base, for better or for worse.
I can't say I've ever had a mould with a burr on the cavity edge. New moulds are CNC machined with the blocks fully closed; it would be well-nigh impossible to create one. An old cherried mould, yes. I don't know if the cavity edge has a burr, the bottom edge of the sprue hole has a slightly raised edge, though, holding the boogers, possibly impeding the pour?
I've never once "heat cycled" a new aluminum mould. Just wash it out with Brakleen and start casting. If I preheat the mould, the third or fourth bullet will be good. As will every subsequent one unless I break my rhythm, thus letting the mould cool down.