Mold temperature

[plaz]

I am still fairly new at casting.. I am in the process of getting a Lyman 45 caliber mold and I understand that it reacts differently to temperature than Lee aluminum molds which I have been using. .How can you tell when a mold is running too hot or too cold? What are the signs?

So far in using the Lee molds I find that a lead temperature of 700 degrees provides the best looking 45 caliber bullets but I don't really know when the mold is too hot or too cold.

[Bret4207]

IMO pot temp is relatively unimportant, beyond that it basically needs to be hot enough to work with your casting tempo. Your casting tempo is what determines mould temp. The more often the mould is refilled with molten lead alloy the hotter it gets. The longer it stay empty the faster it cools. So you have to figure out what your casting tempo or rhythm is and adjust your pot tempt to that. Cool moulds don't fill well and the boolits often are incomplete and have wrinkles. Overly hot moulds take an unusually long time for the sprue to solidify and often you'll get smearing on the blocks.

Iron tends to be able to be run a bit "cooler" than aluminum. I believe thats simply because iron hold heat better.

[RobS]

Adding to what Bret4207 said on too hot of a mold temp is the bullets will come out frosty or should I say overly frosty. I don't mind a small bit of frosting on bullets and have not seen any difference regarding point of aim and/or point of impact. The start of frosting is a point where the mold is starting to over heat.

[Doc Highwall]

My most accurate bullets are when they are just starting to frost and you can see that the mould fills out perfect.

[mooman76]

Yes, iron moulds take longer to heat up but once hot they retain the heat better so you should be able to turn the pot down some. Like stated there are allot of other factors in there. After you practice some more you will get it. If the bullets are wrinkly you mould or the lead isn't hot enough and when they ger overly frosty and take too long to solidify, it's too hot. I like to start out hotter than I need and as I see I'm going good and don't need the heat so much I gradually turn the heat down to settle in. You know you are good when you get a good rythem going and they drop real easy.

[runfiverun]

you can easily establish what i call the cruise speed.
you aren't hurrying but not messin around.
pour, watch sprue suck in, hesitate [ 2 count] open, dump and re-fill.
if i have to vary this speed much i adjust the pot temp.
you should see a nice grey color to the boolits for the entire session once you hit mold temp of about 350*

[geargnasher]

Mould temp is everything.

Hot alloy in a cool mould will not make good fillout. Cool alloy (600-650*) will make beautiful boolits in a 400* aluminum mould, and you can (and must) get your production going (3+ pours a minute) to keep this up, but once you get the mould up to temp you neither have to slow down and cool off nor frantically try to keep up. You can keep the steady pace forever.

You may discover that the Lyman .45 caliber moulds tend to overheat, or overheat just the band section while the noses are still not even frosty. I have to fight constantly with my two-cavity Lymans on this, but it can be tamed somewhat by holding the mould upside down for eight-ten seconds after the sprue just barely sets, keeping the heat migrating toward the heavy nose portion of the blocks.

Preheat the mould before casting either on a hot plate, or by holding the bottom 1/4" into the melt until lead doesn't stick when you pull it out. Dunk the anvil of the sprue plate in too, get it good and hot before casting. Your sprues should set in 3-5 seconds, and your boolits should look like they are made of the dull side of aluminum foil after about 2-3 minutes cooling on a towel.

Gear

[lwknight]

All good answers. I can't really add anything to that.