Lead thermometer

[Gundogx2]

Well I can’t find my lead thermometer after the move it was at least 35 years old dial so what is everyone using these days now I’m in the market


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[Hossfly]

Have a PID on lee 4-20 pot and a dial Lyman for melting wheel weights.

[Beagle333]

Those Big Green Egg smoker thermometers work just fine. (The Tel-Tru brand). Only about 23 bucks.

[BigMoney_NoWhammey]

Second for PID. Just set temp and not have to adjust pot. Have a lyman thermometer I was using before and would buy it again.

[Maven]

Like Beagle 333, I use a Tel Tru, but it didn't come from the Green Egg smoker: Very pleased with it + it is adjustable to a certain extent.

[monadnock#5]

I like a thermocouple. Just my preference though.

[GregLaROCHE]

I’ve never used a thermometer. I just look at how the boolits cast. Maybe having a better idea of exact temperature is a good idea and may improve results or at least help you to get what you want faster with less culls. Thermometers made for casting aren’t cheap. I’ve always reasoned, that instead of spending the money for a thermometer, I might as well get a PID and have complet control of the lead temperature. I hope one day soon, a PID will find its way to the top of my wish list.

[Randy Bohannon]

The Tel Tru’s are as good as they get, USA made in NY. I have a RCBS that has been very good cost more than the Tel Tru’s and made off shore if that matters to you.

[Martin Luber]

Find them free in side of the road junk BBQ units..

[kevin c]

Thermocouple attached to a PID is what I use now.

[Gundogx2]

Thanks good info


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[justindad]

I may decide I am wrong fairly soon, but I intend to use an infrared thermometer.

Get lead very close to its [known alloy] melting point to calibrate the emissivity. Two other points for ballpark emissivity checks are the pot’s MIN & MAX temperatures, which are in my manual (test with pot 1/2 - 3/4 full of lead). Actually, the MIN temp number may not be good if the alloy is not molten at that point. A full pot may not have a constant temperature throughout the material, but a nearly empty pot will have errors from the radiation coming from the walls of the pot. Precision will be there, but not as much accuracy.

I just got my first two molds in the mail today, and they have thermometer taps, which will hopefully compensate for the errors associated with IR in the pot. Now that I think about, the temperature range of the mold thermometers may help calibrate my emissivity value in the IR thermometer.

[Mike W1]

I didn't write the following but have reposted it several times and it does make some sense.

Before I retired from Zeiss, at least 2-3 times a year I had to engineer systems that would measure the exact temperature of machined parts prior to measuring their dimensions. (Engine blocks, heads, etc. in Big 3 auto plants.)

So I've done more than my share of study of temperature measurement methods. Let me say categorically that these non-contact "laser" measurement systems are almost worthless. They measure infrared radiation from the target, and that radiation varies wildly with what is called the "emissivity" of the
surface.

The industrial suppliers of these things claimed that they could tell me a temperature within 2-3 percent of displayed value, IF we sent a large number of samples to them so they could measure the emissivity and calibrate their sensors. Any time a sensor required replacement, they had to go through the whole rigamarole again. Any time the surface finish changed, ditto.

Without calibration, and given unknown surfaces, they wouldn't guarantee accuracy to better than 25% of the displayed value! And that's industrial grade equipment costing thousands of $$. Bottom line, if you calibrate a Harbor Freight instrument against an accurate contact thermometer, you may be within 5% for the exact object you calibrated for. Any other object, you can be wildly off.

BTW the laser has nothing to do with the measurement process. It's just an aiming aid.

Best method is a low-mass thermocouple or RTD device, (thermistor). These are not expensive. Some under-$100 Volt-Ohm-Meters come with a thermocouple probe. I have had two of these, and they worked pretty well. I've never stuck one into melted lead, but there are versions that are encapsulated in ceramic which I would.

[justindad]

I agree with that Mike, and I have also engineered an IR system for an in-process manufacturing check (only once). I did not need such a high level of precision as the guy from Zeiss, which is important.

A bigger & more elusive factor in using IR for casting is understanding heat reflections from other surfaces, which have an additive affect on the measurement.

If errors from using IR are my greatest source of variation in the final boolits, I’ll be happy.

Will the IR errors translate to large boolits errors? It depends

[justindad]

The IR was beyond terrible, due changing oxide content on the surface of the molten lead. I’ll report back if I ever get it working, but most likely I’ll be using a TC.

[high standard 40]

I have a Tel-tru and it reads pretty close to my PID.

[Cast_outlaw]

I bought a Lyman digital thermometer but it gives error messages constantly I think the thermocouple that came with it is no good so I bought and installed a pid on my lee 4-20 it’s great even though it’s in centigrade

[BamaNapper]

I considered one of the IR types for casting ingots in the back yard. Would it work for getting an idea of the temp and avoid hanging a thermocouple in the melt? Maybe monitor the tempo of the pot itself?

That's the thought and question that came to mind when I read this post. What are we looking at? A thermocouple on a PID or voltmeter is a sweet solution on the bench when casting boolits, but might be a nuisance when melting range scrap in the back yard. You'd have a power cord and the thermocouple to deal with. I can see a stick thermometer being handy in that case as you can pick it up, poke it through the trash, take a quick reading, and set it aside. All can be done one-handed, even with a glove on.

[Conditor22]

IR types don't work on reflective surfaces.

monitor the pot. I try to keep the heat down and figure on 15 to 20 minutes for the lead to start melting.
IF it starts melting faster (and is not a hard alloy) I turn down the heat, slower --turn up the heat. you quickly get a feel for what the flame would look like and the setting on your burner.

when the lead has melted you can put a thermometer in and see how hot your flame was set for and adjust for the next time.

[Cosmic_Charlie]

I think mine is an RCBS branded one. Just a simple dial type. Use it in my 4-20 pot. Easy to keep it at 700 deg. which is what I cast at.