2-part question about HEAT

[Marlin Junky]

Has anyone calibrated their hot plate and if so, what temp do you set it on to pre-heat a Lee mold? 'Nuther part... and what did you use to calibrate the hot plate? Would laying a casting thermometer across the hot plate be sufficient to get a decent reading?

The reason for all the questions is that I've decided to give aluminum molds a whirl but typically crank my 750 watt hot plate up to max temp to preheat my favorite RCBS molds (for as long as it takes to bring my Master Caster to approx. 760F). When I cast my first 1-3 casts my boolits are usually heavily frosted but with my relaxed casting rate, the mold temp drops quickly enough and I like a HOT mold for applying Bullplate. Anyway, I'm afraid this routine will wreak havoc on a little Lee mold, so I would like to know how much to back the hot plate off.

Thanks for your input,
MJ

P.S. I think I may also have a 600 watt hot plate if that would be better for an aluminum mold.

[BABore]

Drill a thermometer sized hole in a block of aluminum and set that on the hotplate. I wouldn't set the thermometer diectly on the element.

I don't use a hotplate, but instead dip the corner of my mold in the melt. With my alloy at 725-750 F I look for how long it takes the sprue to solidfy. 10+ seconds is heavily frosted and too hot, but that is where I start at and work the temp down with a cooling fan between casts. When I hit 3-4 seconds freeze time I'm running at the correct temp. Your times will likely vary, but this is a good indicator that's repeatable.

[11B-101ABN]

I use a temp controller from AUBER INSTRUMENTS auberins.com to control my two Lee Pro-4-20 pots, and it stays within 2 degrees of setpoint. The PID controllers are about $40.00 and you can use it as a thermometer also. It worked so well with the Lee pots, I got another one to go on my hotplate. I put a round aluminum 1/2 inch thick and 7 inch diameter plate on the hotplate with a hole drilled in the aluminum the size of the thermocouple. Total dollar outlay for each unit is $40.00 for the controller, $14.00 for the thermocouple and $19.00 for the solid state relay. If you just want it for a digital thermometer, leave off the relay, but it sure is nice to turn it on , set the temp and forget it. You only need basic wiring skills to put it together, and you don't have to play with the knob to get your temp just right anymore.

[selmerfan]

I have a controller on my heat plate, the rheostat that came on it. I run it on max with the molds on it to heat up while the lead is heating. I don't worry about the frosting, it goes away after a few casts. It's easier to cool the mold than heat it up...

[Charlie Two Tracks]

I use an old electric Sunbeam frying pan for my molds. It goes up to 460 deg. and that's what I set it at for heating my LEE molds. Seems to work.

[lwknight]

If you aer talking about setting ther hotplate so that you can just go off and forget the mold and it stay the right temperature , about 1/2 throttle worked for me. You just have to experiment. Its not rocket science.

[gray wolf]

I use an old wood stove thermometer, the one with a spring and magnet on the back,
dial on the front. I don't have a hot plat so I use the electric kitchen stove, same thing.
I found that with it lying flat on the stove element I adjust the heat so it reads 600* and that gets the mold to about 450*. It works for me. Start low, if you need more heat just turn it up a bit. Like it's been said, it's not rocket science.