Calibrating a thermometer idea

[oneMOA]

Recently, since I'm a new caster with all kinds of issues the temp of the allow comes into question. I have a Lyman thermometer and I'm not sure how accurate the tool is. A search of the forum didn't turn up a reliable method of calibration so I'm wondering if anyone has tried a digital infrared thermometer. I have one but it doesn't work well on reflective surfaces. I'm think a ladle held down into the alloy to come to full heat and then brought to the surface and immediately read with an infrared thermometer may give a fairly accurate indication of the alloy temp. Comparing this read to the read of the dial temp guage already in the alloy should be pretty close if the guage is correct. Maybe a black iron flat washer held under the surface with the ladle for a bit then released to float where it can be read with the IR Thermometer. What do ya think?

[Garyshome]

I don't worry much about it. I suppose you might stick a piece of steel in your pot, then pull it out and check with the digital.
It's all relative if it's too hot cool it off of it's too cold heat it up, Take note of what the thermo says, when you hit the sweet spot.

[jsizemore]

I took a 2 week course on gauge calibration while in the military. If you don't have the proper equipment it's a useless endeavor.

When you get to melt point of a known substance, mark your gauge. If you push the limit of your gauge then it's ability to repeat readings is compromised over time. The material loses it's flexibility. Ideally whatever your operating point is should be around the midpoint of the gauges capability. For example, if your operating pressure is 40-60psi, you want a gauge that reads 0-100.

[oneMOA]

I may be thinking about this in terms of an amatuer, which I am when it comes to casting. It would seem after reading many post on this forum, that the proper casting temp for Lyman #2 is 710 deg. I know an experienced caster can look at the alloy and tell when it's "Right" but it would seem that a "formula" would be a good thing. If I am to bake a turkey in the oven there is a recipe with a cook time and temp and it comes out right every time. I believe that an accurate measurement of the casting alloy is essential to the effort of casting and for the newbees like myself would make the process more rewarding by eliminating the rejects and frustration in trying to cast good boolits.

I believe that if the correct formula for Lyman #2 is 710 deg alloy and mould temp of 450 deg would produce good boolits, the one variable is the correct alloy temp causing my frustration and many others like myself. Maintaining these temps is for another discussion, but for now just knowing the temperature goal, and how to know when I get there is the question. There have been more than a few posts on this forum about error in the analog thermometer. There have also been suggestions of calibration by a specialized lab, (expensive) some have gone to PID, (expensive).

I may be hung up on this temperature thing, simple because I don't know, as a newbee, where the "Sweet Spot" is, nor can I look at the melt and determine by the color, if any, what the temp is. I know temp is important, just don't know how to accurately measure it and thought someone may be using an IR Thermometer sucessfully for this purpose. I know my Lyman analog may be as much as 200 deg off to the high side and others complain about that much error in the gauge, which would be high enough lead temp to vaporize at over 900 deg.

[dragon813gt]

Buy a known alloy and melt it. This is your only real option when dealing w/ casting temps. You can stick it in a bot of boiling water but this is going to be at the bottom of the range. You won't be vaporizing lead at 900 degrees. It's boiling point is much higher.

[bangerjim]

You ARE overthinking it! Don't worry about being 1 degree off. If you are planning on using one of those HF IR pieces of carp, don't bother. It will be just as much off as your bimetal thermometer.

I have lab quality equipment I use and have cheked the HF IR units against a known accurate IR ($250) unit as well as tracable t/c's and RTD's. There is a significent margin of error!!!!!!!

And what we do is not rocket science. If you are within 30-40 degrees of where you want, you are just fine.

Experience is worth FaaaaaaaaaaaR more than worrying about the cal of your thermometer!

Just get out there melt some lead, cast some boolits, You WILL learn when the temp is right. Use thermometers as a rough guide only. Look, touch, and feel are far more indicative of correct temps.


And heat your molds to CASTING TEMP, not 450F! IF you do that, you will get perfect wrinkle-free boolits from the 1st drop. I do.

I use no controller, thermometer, or IR device when melting or casting......and get perfect boolits.

Just do it. Don't overthink it.

bangerjim

[country gent]

One thing to remeber is even if your thermometer is off. a reading of 700 degrees is always 700 degrees on it so even if off 50 degrees the comparative temp is the same also. So if your alloy casts good at 700* on your thermometer the next time at 700 is the same basic temp. WHat would be an issue is if it vvaries from use to use by any amount. As long as it repeats even if its off its off the same.

[bangerjim]

One thing to remeber is even if your thermometer is off. a reading of 700 degrees is always 700 degrees on it so even if off 50 degrees the comparative temp is the same also. So if your alloy casts good at 700* on your thermometer the next time at 700 is the same basic temp. WHat would be an issue is if it vvaries from use to use by any amount. As long as it repeats even if its off its off the same.

EXACTLY! That is what we call in my business "repeatable error". May not be dead on cal, but it is ALWAYS off the same exact amount! All the time......every time.

"good nuff fer gubmint work". In the old days, we just "bent the needle" to bring a piece of equipment back into what the reading needed to be. Today with everything digital, it is a bit more difficult to fudge it. So you live with the KNOWN repeatable error deviations.

banger

[JonB_in_Glencoe]

another rule of thumb, is to have the alloy at 100ºF above liquidus temp.
SO...
leave your thermometer in the melt, shut the heat off and allow to freeze, watch the temp at that time, then turn on the heat and record the melt temp. Those two should be fairly close, then try casting with the alloy 100ºF hotter than that. It won't matter how from off your thermometer is from Zero.
Good Luck,
Jon

[John Boy]

Just get out there melt some lead, cast some boolits, You WILL learn when the temp is right. Actually one doesn't need a thermometer to cast good filled out, sharp flat base bullets ... bring the pot temperature up and hold it there so when the mold frosts the sprue puddle in about 5 seconds - cut the sprue. That's all there is to it!

[montana_charlie]

If I am to bake a turkey in the oven there is a recipe with a cook time and temp and it comes out right every time.
Somebody, somewhere, had to play around with different temperatures, different turkey weights, and different times to come up with that 'recipe'. It also requires a controlled environment (the oven) to reproduce the predicted results every time, without fail.


I believe that an accurate measurement of the casting alloy is essential to the effort of casting and for the newbees like myself would make the process more rewarding by eliminating the rejects and frustration in trying to cast good boolits.
In my way of thinking, all of the information necessary to cast bullets successfully is posted on this website. If a certain amount of experimentation is needed in order to produce good bullets in 'your' environment, then success in that should be even more 'rewarding' that simply following directions ... and being frustrated when that doesn't produce the desired results.


I believe that if the correct formula for Lyman #2 is 710 deg alloy and mould temp of 450 deg would produce good boolits, the one variable is the correct alloy temp causing my frustration and many others like myself.
If those parameters (710° and 450°) are the elements in your recipe, the alloy 'variable' can be nailed down by timing how long it takes for the sprue to harden on a freshly poured bullet.

The 'environment' (variations in ambient temperature) will play a role in this, but it will be mainly determined by the heat in the alloy ... as long as you control mould temperature.

You are looking for a sprue hardening time of about five seconds.

Good luck ...

CM

[dikman]

I agree with bangerjim, inasmuch as it's not rocket science and if you do enough casting you'll gradually learn what works and what doesn't. If accurate temperature control is so important to you, then a PID controller is the only answer (good luck trying to keep accurate temperature any other way). I guess they're "expensive" to buy (as a made-up unit), but it's all relative, once you've got one you won't worry about the cost due to the ease of control it will give you.
Or you build your own, much cheaper.

[theperfessor]

Boil some water, distilled if possible. It should boil at 212F at sea level, a little lower as you go up above sea level. Get a little pure lead, it should melt/freeze at 621F. If your thermometer is close to this it is accurate enough for casting.

I've NEVER had any good results using an IR thermometer for anything related to casting, YMMV.

I also have a home built PID and wouldn't cast without one anymore.

[oneMOA]

I think I need to explain my goal in boolit casting. First off, I am not interested in casting ordinary boolits for plinking or casual target shooting. For the lead boolits I shoot and the several calibers, I estimate I have on hand 60,000 assorted boolits all made on a production machine and lubed on the same. I am only interested in casting precision boolits which I don't seem to be able to buy, or I would. My userid is "one MOA" and I am on the search for boolits and ammo that will achieve that goal. I will be loading large boolits in the 535 gr range as that is what works best in NRA BPCR competition and I will be casting these large boolits using my own alloy (20-1) or if that fails then certified foundry alloy of 20-1. It is not necessary for me to reinvent the wheel when the winning shooters are using this combination, I'll go with that.

I have no intention of scronging for lead at the local scrap yard, or the local range, again I am searching for precision boolits and the only way to predict the outcome of a casting session is precision alloy, cast at precision temps with the least amount of variables. I have on order a PID, thermocouple, SSR and other components to build a precision controler for my RCBS Pro Melt which will give me precise alloy temps. Again my goal is precision boolits for the NRA BPCR Silhouette game in my rifles and nothing else.

[Maven]

"Boil some water, distilled if possible. It should boil at 212F at sea level, a little lower as you go up above sea level. Get a little pure lead, it should melt/freeze at 621F. If your thermometer is close to this it is accurate enough for casting." ...the perfessor


What Keith said, as it's excellent advice!

[leadman]

oneMOA, to achieve your stated goal with the least fuss a PID controller would be of benefit to you. I too like accurate boolits and have achieved less than 1/2 MOA with several of my rifles.
A PID controller will control the temperature of your alloy within 3 degrees and is repeatable. As long as ambient temperature is the same, you are using the same mold, same alloy, casting at the same speed, same pressure on the poured alloy, and you cut the sprue and refill the mold at the same time you should produce boolits as close as possible.
The above is very difficult to achieve so I weigh the boolits and group them by weight. The spread depends on what I am using them for.
If you want info on a PID PM me.
Good luck in your quest.

[dikman]

oneMOA, I applaud your dedication to your goal. In view of your stated requirements, however, (precision alloy, cast at precision temps with the least amount of variables) I'm surprised at your original post and the suggestion that an infrared thermometer could be used. There have been quite a few posts on here pointing out that they won't work on a molten lead surface, and your idea of using a black washer submerged in the lead (or some such device) is hardly what I would consider "precise". For your needs a PID controller is the only answer, I can think of no other way of being able to control the temperature of the lead with any degree of accuracy and consistency.

My PID keeps my ProMelt within +/- 2 degrees C once it's up and running.

[jsizemore]

That's why the OP was asking cuz he don't know. Search on here is frustrating at times.