I have never used a Casting Thermometer. I can see the use for such and would like to know are there any one better than anyother I might see for purchase. Also give a brief explanation of the their application and what might be learned by their use. Reference a to web article is fine but also in your own words give your reason for using such.
I bought an infrared thermometer from Harbor Freight on sale for under $20. It reads over 900 degrees F so I thought it would be suitable for bullet casting and would have other uses as well. Then I read somewhere that the shiny liquid metal, being too reflective, would cause under reads. But if you measure before you skim the dross, the dull dross covered surface would yield a much more accurate reading.
I got to thinking about this issue. The infrared thermometer measures the surface temp of the metal. Is the metal hotter at the bottom of the pot nearest the flame? Given that heat rises, it it hotter at the top of the pot? Or, is there any significant difference at all?
Could someone with a true casting thermometer answer this question?
Good Casting, like good loading and good shooting is a result of carefull experimentation to see what works. To be able to repeat the results accurately and consistantly requires good notes on the conditions that lead to the favorable results, as well as the proper equipment to recreate the same conditions.
Not all molds cast well at the same temp, and even if they do, the bullet will weigh more or less depending on the casting temp. I have some molds that cast just fine at 750F indicated (on the Lyman thermometer). Others don't produce good bullets until the temp is 800. Reference to my notes allows me to begin casting good, consistant bullets faster and more often.
Another consideration is that as the casting pot empties, depnding on the heat source, temps may begin to climb, resulting in different bullet weights as well as increased oxides forming. My big 100# pot has to monitored closely as I'm casting 525 bullets because it's propane powered, so the gas has to be reduced as the pot empties to maintain the desired temp.
The infrared thermometer is a great tool to verfy the reading of the casting thermometer. Take a surface reading w/infrared and compare to the casting thermometer held to read the surface. Infrared also lets me know that my pre-heat arrangement, a single element hot pad, has the molds at the temp I want, and if wind/air temp is affecting it.
And yes, temp in the pot does vary. That's why I ladle from the middle, take temp reading from the bottom on the Lee bottom pour.
That's my $0.02.
Last edited on Sat Aug 8th, 2009 10:38 am by Dollar Bill
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The most "serious" use is when I am smelting wheel weights. One zinc wheel weight melted in a 100 lb batch of bullet alloy can ruin that alloy for casting. Zinc contaminated alloy will not fill out a mould properly and there is no practical way to remove it from the melt.
However, if you use the thermometer when you are melting wheel weights, and keep the melt at 650 degrees and under (that is hot enough to melt Wheel weights) the zinc weights will float on the top to be skimmed off. Zinc melts at 787 degrees and I prefer a 100+ degree separation to account for possible "hot spots" in the melt. I use a Fish Fryer/Turkey Fryer with a 12" cast iron dutch oven to melt in. It is EASY to regulate the propane to keep the heat where it should be.
Without a thermometer, it would not be possible to accurately determine the temperature.
I also like to use it when casting from one of my RCBS bottom pour pots. Different moulds seem to require a bit different temperature to cast - kind of a "sweet spot". The thermometer allows me to do this with repeatability.
I had a Lyman thermometer and discovered that it was NOT accurate (I have heard that from others, also). I bought my present thermometer from Bill Ferguson (the Antimony Man):
Stephen Perry wrote: I have never used a Casting Thermometer. I can see the use for such and would like to know are there any one better than anyother I might see for purchase. Also give a brief explanation of the their application and what might be learned by their use. Reference a to web article is fine but also in your own words give your reason for using such.
When I do some serious smelting, serious buying of alloy or casting such as smelting WWs, I can carefully watch my temperature using a gas actuated thermometer and weed out the dreaded zinc. Another is I can determine if an alloy is "pure" linotype if it melts around 464 F. Once, a seller told me that his batch was PURE linotype and only to find out, I took a sample and smelted it in my pot only to find out that the sample batch melted at 700+F. However, it casted well!!!
Needless to say, I was able to go back and proved to him that is was NOT linotype and he ended up selling all 1347 lbs for only $200.00 all in 1 lb ingot form.
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I think the guys have said it all, or most of it. I would add that melting pot settings are not all accurate. Lee pots have settings but don't tell you what the temperature is. I have tested three of them and thy were all different. What if you are using a home made pot made from steel pipe heated by bottled gas like propane ? The only way to control temperature is by gas pressure and/or height of pot above flame, but you can't do it without a thermometer.
As others have said, moulds have their own temperature characteristics and two identical moulds can have different temperature preference. In general, though, the bigger the calibre the cooler the alloy needs to be.
Different alloys have different melting temperatures. More antimony = lower melting temp. You don't want alloy temp too much higher than melt temp, 100F i a fair rule of thumb.
I see a member reports an inaccurate Lyman thermometer. Few are dead on, but my Lyman is close. RCBS offers a similar one. Bill Ferguson offers one and there are suppliers of similar thermometers in most cities. Any reputable make should be OK.
I would just like to toss in a recommendation for buying one from Brownells. Mine went bad a number of years ago so wrote asking where to send it for repair. They replaced it free of charge. Don't think warrantys get any better than that!
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