Is it important to cast at a specific tempeature

[Bret4207]

How much of a temperature variation would I have to have to see a weight variation? I tend to toss any cast bullet with flaws back into my pot so after that my mold is above a certain temperature. I've never experience overheating my molds either but do you have a technique to maintain a stable mold temperature. Obviously setting a mold on the floor is not good. Would a hot plate on medium maintain a mold temperature do you think?

Why would you be putting the mould down in a casting session? Pot temp is not critical, MOULD temp is. It's that simple. You vary mould temp through your casting speed. The more often hot alloy goes in the mould, the hotter it gets/stays. If you cast slow, spend time looking at what you just cast, get sidetracked, then your mould cools down. Worry about what the castings look like after you get down. Not like you can grab them right out of the mould anyway. Cast, cast fast until the sprues take an abnormally long time to cool and then slow down a little. Cast the way the mould tells you it needs to be handled.

 

[burbank.jung]

I'm still working on my cadence and setup. Every so often I need to clean up the scrap lead from the sprue plate.. and toss it back into the pot.

 

[quicksylver]

most of what's above, love my pot therm. I start fluxing at anything above 650deg. start casting and try keeping my alloy at 725. I also try and keep my flow the same by watching the volume in the pot and adjust acordingly.

 

[burbank.jung]

most of what's above, love my pot therm. I start fluxing at anything above 650deg. start casting and try keeping my alloy at 725. I also try and keep my flow the same by watching the volume in the pot and adjust acordingly.

How much of a percent do you let your pot level drop? What steps do you take to flux?

 

[JustJim]

For me, the biggest improvement in casting results came when I started using a metronome to time my casting cadence. I eventually went to the second hand on a clock, but that was just for convenience: I got tired of mentally listening to the theme song from "Jeopardy" while waiting for the sprue to harden.

When it takes longer than I'm expecting to fill the mould, I know it is time to add lead, flux, etc. For example: I watch the clock as I cast. I start a pour when the second hand is on 12. With a particular mould, I might expect to take 5 seconds to fill a cavity. When the level in the pot drops to the point it takes longer than 7 seconds to fill the mould cavity, I stop and add lead, flux, etc. This is typically in the 1/4 to 1/3 full range.

When the lead in the pot is up to temp, I stir in about 1 heaping tablespoon of sawdust and light the smoke. When flames go out, I stir for another 30 seconds or so. Then I start another round of casting.

 

[quicksylver]

How much of a percent do you let your pot level drop? What steps do you take to flux?

I don't like to get much beow 50%but it depends on how well the alloy is flowing.As I said I adjust as the pot stats to empty to maintain a good flow and a good sprue.My fluxing is done with wood shavings as I cast in our wood working shop and always have a good supply. as I said I flux at least twice when I first start up the pot and twice after returning the sprues and culls it takes no more tham a soup spoon full. BTW I keep my mold on a hot plate when fluxing and waiting for the tempt to rise. Dan

 

[fiver]

my pots always full.
i put the sprues back from my hand before opening the mold.
and there's ingots sitting on the steel cover heating up.

yep i keep the pot full.
it has more mass and fewer/lower temp swings.
the steel cover adds more mass, and the ingots on top are nice and warm when they go in.

as far as fluxing.
that gets done in the initial melt/clean and then again in the big mix.
only occasionally do i clean/skim, or return oxides [fire] in the casting pot.

 

[Bret4207]

I'm still working on my cadence and setup. Every so often I need to clean up the scrap lead from the sprue plate.. and toss it back into the pot.

Then you're sprue plate isn't hot enough, alloy should pretty much run off it and leave it pretty clean. If you are bottom pouring this may not help, but if you can ladle alloy over the sprue plate or, if using a ladle, overfill the cavities by a large degree so that nice toasty alloy runs off the mould and back into the pot that will help immensely. Yes, you'll have little freckles no matter what, but you shouldn't get build up if the plate is anywhere near hot enough. You will have to have a good heat source to keep the alloy up to temp if you are putting stuff back into the pot. If the alloy in the pot is cooling too much you should be able to feel the difference if you are ladling. With BP, I dunno how you judge it.

 

[fiver]

the sprue cut will let you know.
turn your mold over when your heating it up.
the plate will be plenty hot.