New Hollow Base Mold Being a Challenge to Cast

[Ian]

Yeah...pretty stunning work there Loren! The timber on that. 40 is unbelievable.

 

[Heelerau]

I have been casting Minnie bullets since the early 1970s, I shifted my casting outfit from the workshop into my blacksmith shop, and ever since have been having grief with this shrinkage from the baseplug. Seems I have to let the mould cool some, and pour slowly. I do not know what has changed. I am using commercial lead ingots assayed at 99.97 purity. I flux well with bees wax as I always have. I have bought finally an infrared heat gun to check temps. I note the gas fired pot is much hotter on the walls than the lead. Another mate who is an experience caster is having the same issues. The mould blocks are brass and the base plug is steel and not captive. I use an fairly large ladle to cast. As. I have said nothing has changed in my technique or casting setup, but it does see to be temperature related. The bullets come out shiny and smooth, not colours to indicate that the melt is to hot.

 

[fiver]

temperature is the key.
brass and steel gain and retain heat at different speeds, if your fighting a shrinkage issue somewhere I'd bet you have too much heat in the mold blocks.

 

[Heelerau]

I am also now going to clean all the vents on the blocks incase they might be restricted . You are quite right about the differing heat retentions.

 

[Heelerau]

Cleaned the ver shallow block vents, looks like problem solved !