Controlling pot temp and other questions

[cs86]

I just picked up a lee 4-20 bottom pour pot and started casting this last weekend. I had a hard time keeping the temp consistent. I realize others use PID kits to help stablize, but without one how do you control it better.

One fear I have is to leave my thermometer in the pot. I'm afraid I'm going to ruin it if I leave it in there for an extended period of time.

Something else I noticed. I could flux the pot and get the other alloys to mix in that would come to the top. I was thinking temp had something to do with helping keep those alloys mixed, but even when the temp was high, those alloys seemed to come back to the surface. I would alway notice how it would stick to my thermometer and I would have to scrape it off with my spoon at times. How often to you flux?

Another thing I noticed, it was hard to control the temp of the mold. When the mold would get to hot it wouldn't make a clean slice, it would look more like it pulled it out. It would help when I could get the mold temp down. I've heard of others using a damp cloth, which I tried. It helped some but I didn't want to cool it to fast and ruin the mold. I could slow way down to let the mold cool more, but I felt like it would of taken forever if I had. Suggestions?

Overall I had great bullets. I was able to avoid rinkles by smoking the mold and everything filled out nicely. For the most part I'm just trying to find suggestions on helping with temperature control for the pot and mold.

[snuffy]

I just picked up a lee 4-20 bottom pour pot and started casting this last weekend. I had a hard time keeping the temp consistent. I realize others use PID kits to help stabilize, but without one how do you control it better.

One fear I have is to leave my thermometer in the pot. I'm afraid I'm going to ruin it if I leave it in there for an extended period of time.

Something else I noticed. I could flux the pot and get the other alloys to mix in that would come to the top. I was thinking temp had something to do with helping keep those alloys mixed, but even when the temp was high, those alloys seemed to come back to the surface. I would alway notice how it would stick to my thermometer and I would have to scrape it off with my spoon at times. How often to you flux?

Another thing I noticed, it was hard to control the temp of the mold. When the mold would get to hot it wouldn't make a clean slice, it would look more like it pulled it out. It would help when I could get the mold temp down. I've heard of others using a damp cloth, which I tried. It helped some but I didn't want to cool it to fast and ruin the mold. I could slow way down to let the mold cool more, but I felt like it would of taken forever if I had. Suggestions?

Overall I had great bullets. I was able to avoid rinkles by smoking the mold and everything filled out nicely. For the most part I'm just trying to find suggestions on helping with temperature control for the pot and mold.

First, it won't hurt your thermometer to leave it in the melt.

Second, at what temps are you attempting to cast? It sounds like you're way too hot.

What type of mold? Is it a lee aluminum? What boolit? If your pot is above 700 degrees for a wheel weight type of alloy, you will have trouble with that AL. mold getting too hot.

Third, the alloys,(tin and antimony) do NOT "float" out of the lead. They oxidize at the surface of the lead, tin oxidizes more easily,, and at a lower temp than either the lead base metal or the antimony. That's why you should stay close to 700 degrees. What are you using to flux with? Sawdust is best. Leave the charred sawdust on the surface of the lead to form a barrier to the air.

Fourth, smoke is for signalling other Indians. Leave it out of your molds! The Lee instructions make good kindling for a campfire. Also, don't use boolit lube to lubricate the mold. It turns into a black mess when it burns off, does more harm than good. Go to a good auto store, find some synthetic 2 cycle oil,(ya know what you mix with gas?) Use that to lubricate the sprue plate pivot, the guide pins, and mold handle pivot. It is made for high temps without burning.

My newest lee 4-20 pot had a temp swing when full of +- 40 degrees. That's pretty normal. Then as it empties, the temp will climb higher. Since I had built a PID for the old 4-20 pot, I hooked the new one up to the PID. Now, I get +-2 degrees, regardless as to how much lead is in the pot.

[454PB]

I'm with Snuffy. Once you have used the lead thermometer to determine what the numbers on your thermostat actually produce, you won't need the thermometer very often.

Control the mould temperature, and don't worry about a 25 to 50 degree swing in alloy temperature. The wet cloth is the way to do that, and don't be timid......you won't hurt the mould.

[cs86]

I'm casting with a Lee alum mold .452-230gr boolits. Fluxing with candle wax. I wanted to try and cast between 600 to 700 degrees. It seemed to fluxuate between 500 and 800. I would try and pick a setting but I couldn't nail it down to something close to a 50 degree fluxuation. I'm sure this would be better if I keep the thermometer in and adjust while it reads. I'm using 2 cycle oil for mold lube. I've noticed as it gets lower that it tends to heat up more.

I will have to try leaving the thermometer in it. Does the thermometer need to set off the bottom of the pot or can it rest on the bottom?

How low do you let the pot get before stopping? I noticed that towards the last part of the pot my molds where starting to look funny.

The reason I smoked the mold is because everytime I had it freshly cleaned and stated casting I would get wrinkles. after I would smoke it. All wrinkles would go away. It just seemed to work for me.

[454PB]

It's normal for the first boolits cast from a cold mould to be wrinkled and shiny. Preheat the mould and you can avoid this. Many casters use a hotplate to preheat their moulds, I prefer a propane torch. I have a spot on the shelf below my casting pot that is the right height. I place the mould handles on that shelf, put an ingot on the handles so it doesn't tip off, then place the propane torch on the floor, flame directed and the mould bottom, and set at a low flame. In about 60 seconds, the mould is up to good casting temperature.

Smoking a mould only covers up other issues, a squeeky clean mould works best.

If your thermostat is allowing the alloy temperature to vary by 300 degrees, it's defective. But, before you condemn it, think about the large volume of metal involved, and how slowly the temperature changes when you turn the dial. You may be over correcting.

I suggest you set the dial at say....number "4", fill it with alloy, and let it become liquid. Drop your thermometer in and just watch it for 30 minutes or so without touching the thermostat setting. If it swings 300 degrees, it's bad.

The thermometer doesn't have to touch the bottom of the pot. As long as it's submerged an inch or more, it will work. On my Lee Pro-4-20, I added a 90 degree metal tab to the edge (using one of the screws that hold the top ring) that is tall enough to hold my RCBS thermometer about an inch off the bottom. My thermometer came with a clip attached for that very purpose.

[cs86]

Does your Lee 4-20 pot make a loud humming noise when the thermostat kicks on? I have a RCBS thermometer but it only came with a handle for grabbing, no clip for the pot. I might have to rig something up. The next time I cast I will try the testing as you suggested.

[gray wolf]

How cold is it in your casting area ? cold air and chilly wind can effect the Temp inside the closed in housing on the pot. That's the housing for the Bi-metal temp sensor, there is no thermostat inside the pot. If that area gets influenced by cold outside air it will keep telling the pot it needs more heat.
Leave the Thermometer in the pot, no need to remove it. I can keep my bottom pour pot to within 50* I cast at 675 * Watch the temp that the metal becomes fluid at and cast 100*
to 125* over that temp. Ain't gonna get no mo fluid. You control everything after that with casting speed.

[prs]

cs86, my Lee 20# pots are fairly "happy" when I let them settle in at about "7" on the dial an when I begin to cycle the moulds to warm them up to temp I drop the thermostat to "6". Dropping spru back into them from 6 cavity moulds does make the temp fluctuate and as the pot empties the temp seems to climb. The PID took care of all of that. Pot on "7", let it settle, switch to the PID controller set to 670F and put pot on High. Sweeeet. I made holders for the thermometer and PID probe with carpenter's galvanized strapping bands. Its like a perforated metal tape about a half inch wide. Band a strip of it about 7" long into a "P" shape, the leg of the "P" gets fastened with one of the existing pot screws, the probe or thermo goes through two of the holes in the upper "P" section with the holes just far enough out of alignment to pinch the shaft. I place the tip of the probe about an inch above and close to the outlet of the pot. The metal dross you are fluxing back in is oxidized tin and that is the $ part of your alloy. Too much heat makes it a real problem, get under 700F and cover the melt with clay based floor sweep or clay based kitty litter. A layer of the granules even a quarter inch thick will help reduce the oxidation and help protect you from splash and water pops. A little saw dust or dry oatmeal makes a good top flux.

prs

[JonB_in_Glencoe]

Typically the best temp to keep tha alloy at is usually around 100º above Liquidus. That is about 650 for WW alloy. Some molds will tell you they like it hotter or cooler...listen to them :)

I leave the thermometer in the melt for the whole casting session. After I get my alloy melted and fluxed, I leave a layer of dross on top, maybe ½" thick. I will spoon some dross from my dross dump can if there isn't enough to cover the melt that thick...some casters use kitty litter for that...what that does is insulate you HOT molten alloy. Not only does that help hold the temperature more constant, if you choose to dump sprues back in, the dross layer keeps them from sinking into the melt...they will still melt in (and seep through the dross), it does take longer, but who cares??? This keeps the sprues from lowering your temperature of the alloy...and there is also some advantage of less oxide contamination too.
Jon

[RydForLyf]

The Lee pots don't do any temp sensing of the lead. Adjusting the knob only controls how much time the element is on, heating the pot. There's no correlation with pot temperature which means setting the knob at "4" with a full pot is a whole lot different than setting it to "4" with an 1/4 full pot.

A PID will set you free. Otherwise you spend all of your time chasing the temps.

-RFL