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Thread: Something I learned last weekend, about temp

  1. #21
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    Quote Originally Posted by geargnasher View Post
    I see people getting fed the wrong information constantly and know where that road will lead: Frustration and probably giving up the hobby because there is too much "witchcraft" involved with it.
    But, you have to hang around here for years, and slowly build up a reputation for knowing something, before you can state that simple truth and not have the 'experts' blowing fuses in unison.

    A person may 'learn the truth' soon after arriving or may know it when he shows up.
    But if he tells what he knows to soon, he won't be believed when all of the 'frosters' weigh in.

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  2. #22
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    Very nice write-up gear. Sometimes it's not just the information by itself, but how it's presented. You presented the info in such a way as to cause me to actually form a mental picture, a movie in my mind, of me standing at my casting bench performing each action that you described.

    Your literacy is showing through.

    smokeywolf
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  3. #23
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    Gear you cain't have all that information in one head you have got to have two. LOL

  4. #24
    Boolit Man Quiettime's Avatar
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    Quote Originally Posted by leadman View Post
    Since the OP thermometer is reading over 1000 degrees and hard to take a reading as there are no numbers past 1000 it might help to adjust it so it reads within the scale ........ head turns on the probe to adjust the needle. .
    For some reason I didn't think you could do that. I have a habit of breaking things...will try, but I think I'm also going to get another thermometer to double check.

  5. #25
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    Gear,
    That was so useful i copied it and emailed it to myself for future reference...thank you for your meaningful and informational posts

  6. #26
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    The post is now stickied? Stuck? pinned up top.
    [The Montana Gianni] Front sight and squeeze

  7. #27
    Boolit Man Quiettime's Avatar
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    Quote Originally Posted by geargnasher View Post
    "Frosting" is an effect caused by two things in combination: The presence of antimony in the mix, and a very hot mould.

    The temperature of the metal going into the mould has zero to do with whether or not the boolit surfaces will have the "frosted" appearance, that is 100% a function of mould block temperature and cooling rate, or rather the SLOW cooling rate, of the alloy. The more slowly an antimonial alloy cools, the more time the antimony dendrite crystals have to form lattices, and the appearance of a textured surface becomes present.

    For example, I can literally pour 800-degree wheel-weight metal into a 200-degree mould and get shiny, wrinkled boolits with rounded edges. I can also pour 650-degree wheel weight metal into a 450-degree mould and make boolits that are so frosted and undersized that they appear as rough and dull as freshly-broken cast iron, or appear as if they were sand blasted. The difference is the temperature of the MOULD, not the alloy. And, of course, the presence of some antimony in the mix. Tin/lead alloy or pure lead always casts fairly shiny, regardless of mould temperature or alloy temperature.

    The general rule for most of the ternary (lead, antimony, tin) alloys that we scrounge up for making boolits is to run the pot below 750 degrees F., or really about 100-150 degrees hotter than the fully-liquid point, and to preheat the moulds somehow (dip a corner in the melt for a while, set across top of pot for a few minutes, or improvise a "mould oven" using a hot plate and metal box) so they come up to casting temperature faster or start out at casting temperature. THEN, as you cast, maintain a pace that is brisk enough to keep the mould hot enough for good fillout.

    Casting good boolits is all about consistency. Constant pot temperature is important, this is what your thermostat and thermometer are for. Constant mould temperature is even more important, and that is controlled simply by adjusting the timing of the various pouring, waiting for sprue to set, cutting, opening, dumping, closing, and refilling operations. Casting boolits is like driving a car on the highway, you have to constantly make slight corrections to steering, throttle, brake, etc. and watch your mirrors, the road, anticipate hills and valleys to keep the speed consistent and in the "zone" that you want to be.

    You'll have to experiment with timing operations and pouring stream adjustment, technique, sprue puddle size, etc. while watching for frosting, rounded edges, filled bases, air bubbles/voids in the bases, wrinkles, shiny spots, frosted bands/shiny noses, sprue flashover time to give yourself clues about what is working and not working with a particular mould, alloy, and atmospheric condition.



    Here's a quick and dirty method that works every time. Turn on the pot and start melting your alloy. Stir it with a spoon as soon as it starts to get mushy and watch the thermometer. Once the metal thins out like thin porridge, keep a close eye on temperature, it should remain constant as the phase changes. Once the last bits of grainy metal go away, the temperature should start to rise again (the metal is past the phase platau). Record the phase plateau temperature and add, say, 150F to it. Allow the alloy to reach this temperature and adjust the pot to maintain it. Spoon in a layer of pine sawdust on top of the melt and stir the alloy gently to flux and reduce oxides. Skim if you want, or not. Dip a corner of your mould down int he metal and hold it there until the alloy no longer sticks to the blocks when you withdraw it, this could take anywhere from 30 seconds to two minutes. Dip the tip of the sprue plate in the alloy too, for about ten seconds, then close the mould and start casting. The mould should suck the pot temperature down 50 or so degrees depending on the size of the mould. Fill, cut, and dump the first few castings quickly and glance at the boolits. If shiny and wrinkled, keep casting culls as fast as you can until they start to fill out and get an even, satin frost all over. From this point on, you can play with the timing and sprue puddle size to control mould block and sprue plate temperature to keep the mould temperature and boolit quality even from nose to tip.

    This works with any alloy, any pot, any pouring technique, and any mould (except non-antimony alloys won't frost, you just look for sharp edges and good fillout with those) and any weather. Don't forget to glance at the pot temperature once in a while and make sure it stays 100-150 above the fully-liquid point that you recorded first thing. It's all up to mould temperature and technique after that, and trust me, quit dinking around with pot temperature, it is not going to do you any good.

    One more thing, to emphasize what MT Gianni wrote, IF your thermometer is off even 200 degrees, if you do as I described above, it won't matter because you only want to obtain an alloy temperature that is a certain amount above fully liquidus with ANY alloy, and your thermometer is good enough to give you that valuable reference point even if it is not giving you an exactly accurate temperature reading.

    Gear
    Wilco

  8. #28
    Boolit Master Slow Elk 45/70's Avatar
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    YUP, this is a lot of good info in one place, well presented..... if a feller can't read the info and understand what is being said , ......well he may need to read it again, Good job Gear
    Slow Elk 45/70

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  9. #29
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    As for the thermometers it doesn't surprise me in the least that the OP's reads 1000 degrees even though it's doubtful the alloy was that hot. I had a heck of time back before PID's trying to get an accurate thermometer. I placed three of them in the same pot at the same time and couldn't tell within 100 degrees what the melt temp was and couldn't tell within 100 degrees what the alloy temp was when casting. This was my original reason for getting a PID controlled pot.

    Most if not all American made lead thermometers are made by Tru-Tel regardless if it says RCBS or Lyman or whatever. None of the lead thermometers I've had were particularly accurate though most were reasonably repeatable.

    Rick
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  10. #30
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    Here are some excerpts from another thread a while ago addressing this same alloy/mould temperature thing, and I wanted to include it here because some things like the behavior of tin above certain temperatures and the truth about which moulds lose heat fastest that I didn't add to my previous posts here (not really needed to address the OP's topic). Rick and I were trying to point out to folks that the alloy temperature is a set-and-forget thing based on alloy composition and melt point, and boolit quality is obtained through all the things we can do to get the mould up to the right temperature for the conditions.

    Quote Originally Posted by geargnasher View Post
    Quote Originally Posted by peterso View Post
    What is the best tempreature for casting bullets with WW?
    Thanks,
    Owen
    Owen, this is one of the best questions I've seen asked here in a while, and an important one I think.

    Rick pretty much covered it, and the most I can do is reiterate and expound.

    Keep in mind that keeping the mould at ideal casting temp (whatever that is for a given mould, it can vary greatly) is the most important thing temperature-wise in casting. This is often overlooked, and folks who cast at a pace too slow for the mould or don't preheat their moulds somehow unwittingly compensate by turning up the alloy heat, and perpetuate the "Crank the Heat" myth. Overheating the alloy has it's own set of issues, for example tin becomes ineffective as an oxidation barrier and viscosity modifier above 750*. If you're casting with straight wheel weights with (presumably) very low tin concentration, you can run a bit hotter, but as a rule you should focus on keeping the mould hot and the alloy as cool as will reasonably cast.

    How hot is hot enough for the mould? A general rule for most of my moulds is about 5-6 seconds for the sprue puddle to set, and then still cut it with the flick of a gloved finger on two-cavity moulds. This is in the "light frost" range, which is what I generally try to achieve. Opinions vary on frost, some like a little and some think it's the devil, it's mostly personal preference.

    Another rule of thumb on temp, the more tin you add (up to 2% content, you shouldn't ever need more) the lower the melt temp of the alloy, and thus the lower your pot temp needs to be. Lyman recommends 100* over liquidus temp, but as another member pointed out recently in another thread it's hard to tell when all the antimony has melted completely. Your alloy may be at full liquidus at 520* in theory, but you might get best casting results at 680* and a mould at 420*.

    In the end, every casting session is different, and to achieve best results you need to know a little about the physics of what you're doing and the things you can adjust so as to be able to "roll with the punches" as weather, alloy, mould conditions, and the phase of the moon change, rather than just remember "700* with WW alloy*, because it won't always cast best at 700*.

    Hope this helps,

    Gear
    [then a lot of not very helpful posts and guesses, another good post by CBRick:]

    Quote Originally Posted by cbrick View Post
    Quote Originally Posted by sqlbullet View Post
    Keep in mind that the composition of your mold will impact this as well. A mold that is more effecient at conducting heat away from the lead into the air will require a hotter pot to maintain temp. In general Aluminum molds will require a slightly hotter pot than steel, cast or brass molds.

    I run Lee and Mountain Molds in Aluminum. And I run my pot at 700.
    Interesting. Conflicting but interesting.

    Your right to run your pot at 700 degrees but a higher pot temp isn't needed to keep your molds at proper casting temp with iron, brass or aluminum. 700 degree alloy can easily keep any mold hot enough or even too hot.

    As an example, your mold casts well at 450 degrees regardless of what it's made of. At 700 degrees your pot temp is 250 degrees over this proper mold temp and 250 degrees higher than proper mold temp will keep your mold at proper temp easily. No need whatsoever for a higher pot temp to maintain proper mold temp.

    If your pot temp is 700 degrees and your bullets aren't forming well due to not enough heat it is not the fault of the 700 degree pot temp. It is a too cool mold, pre-heat the mold or cast faster to get the mold temp up, 700 degrees is plenty hot enough to do this.

    Rick

    Quote Originally Posted by geargnasher View Post
    It's astonishing to me how many people have been casting for many, many years and never snap to the fact that mould temp is everything. The only criteria for pot temperature are determined by the specific needs of the alloy itself, NOT the mould's needs.

    Mould temperature is reached by preheating (either external heat source like a hot plate or dipping in the pot lead, or by casting a bunch of culls really fast until it comes up to temperature), and maintained by casting rhythm.

    Bottom line with most casting alloys that contain some tin is keep it under 750* due to negating the good effects of tin and creating excessive oxidation rates, and the alloy should be enough above full liquidus to flow well, usually IME 150-200 degrees or so above melt point and at least 100 above liquidus.

    If you have an aluminum or brass mould that has a high thermal conductivity, especially large-caliber moulds which have lower mass than equivalent moulds of smaller caliber, the solution to keeping them hot enough to cast well is to HURRY UP, not TURN IT UP.

    Brass loses heat the fastest by far, aluminum next, then the various iron/steel alloys. This is a big consideration when ordering a mould with a particular design/shape/weight of the cavities.

    If your sprue plate is disproportionate to the blocks, and the blocks lose heat faster than the plate, cast fast enough to keep the blocks at a happy temperature and invert the mould and quench the sprue plate on a towel briefly after the pour like Bruce B. and Goatlips have demonstrated. If the opposite is true, pour a bigger sprue puddle to impart more heat to the sprue plate.

    Running a casting session is just like driving a car through town, a constant state of observation and correction. You just have to pay attention to what the boolits are telling you and know what things you need to adjust for correction, while keeping basic information like oxidation threshold of tin (speed limit and stopping distance, keeping with the driving analogy) as basic rules of function.

    Gear
    There's a three page thread going on here in Castboolits that asks "what temperature do you cast at?", in which the majority of the replies demonstrate that few people are aware of or consciously consider the difference between mould and alloy temperature and how that relates to boolit quality. I tried repeatedly to point out what I've pointed out here, but that was a different crowd I suppose.

    Another good thread with high volumes of hard data about boolit weight variances, mould temperature, and alloy temperature is in here somewhere too, Goodsteel posted all about his experiences with just one mould and proved beyond a doubt that THIS STUFF MATTERS.

    Gear
    Last edited by geargnasher; 03-31-2014 at 02:29 PM.
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  11. #31
    Boolit Master



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    Exactly!

    I'll add to that the sprue plate temperature. It is something that few people seem to consider and yet it is as important as mold temp. The sprue plate doesn't have near the mass that the mold blocks do plus it spends time sticking out in the air cooling it rapidly. It is very difficult to get good boolit bases with a sprue plate that is too cool just as it's difficult to get good driving bands with a mold that's too cool or HP noses with HP spuds that are too cool. Always pour a generous sprue puddle to heat the plate. Don't look at it as pouring lead on the plate, look at it as pouring HEAT.

    Rick
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  12. #32
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    "Pouring heat" is an excellent way to visualize the sprue puddle. I like to run my sprue plates very hot and pour a very large sprue puddle that stays molten longer than the metal in the cavity. This reduces base voids and bubbles/porosity since the cooling/shrinking metal inside the mould has a liquid pool from which to pull rather than pull itself apart inside as it shrinks. If the sprue freezes last, the base will be fully formed and at full density.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  13. #33
    Boolit Master
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    This was an outstandingly good post from one of the true masters in the field. But you should know that gear is a really nice looking red head and she sells longeray at Dillards.
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  14. #34
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    Slightly off topic, but maybe not too much. I seem to remember something in one of the Handloader Bullet Making annuals that used pure lead to calibrate a thermometer. Take the lead up to 700 or more and then turn off the pot and record readings every so many minutes as the lead cools. Should show a plateau in the resulting curve. I don't remember at what temp that plateau should occur but will check the next time I'm in the shop.
    John
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  15. #35
    Boolit Master Driver man's Avatar
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    Well written in plain English .This article should be read by every new caster and most older ones.
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    To fly-and Lo! the bird is on the wing

  16. #36
    Boolit Master DrCaveman's Avatar
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    Great timing here. I just made a few alloy changes and was having some issues
    Couldn't figure much out, all I knew was that fill out was bad
    Heating the mold waaaay more was the only fix I found
    I think you just answered all my questions

    Thanks! Great post

  17. #37
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    Quote Originally Posted by alamogunr View Post
    Slightly off topic, but maybe not too much. I seem to remember something in one of the Handloader Bullet Making annuals that used pure lead to calibrate a thermometer. Take the lead up to 700 or more and then turn off the pot and record readings every so many minutes as the lead cools. Should show a plateau in the resulting curve. I don't remember at what temp that plateau should occur but will check the next time I'm in the shop.
    That would clear up the OP's thermometer concerns for sure. IIRC the melt point of pure lead (key word PURE!) is 621 point sumphin-sumphin degrees F. I think the freeze point is the same, and the temperature should hold steady at that temperature while the phase change completes. That Handloader article is using the same principle as determining the full-liquidus point of the metal, or the very end of the "mush phase" as the alloy melts from a solid. In case I confused anyone who's worked with pure metals or with eutectic or pseudo-eutectic boolit metal like Linotype, I failed to mention earlier that some alloys have no "mush" or "slush" phase, but change phase suddenly at one temperature like a pure metal does. I was speaking in the context of typical ternary boolit metals like wheel weights or similar. It isn't likely that many of us have cast with true eutectic metals, but have probably come close once or twice if we messed around with linotype or Lyman #2 a lot.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  18. #38
    Boolit Master

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    I need to clear something up. The article I referred to used linotype(not pure) to generate a cooling graph. The lino had a plateau at about the melting point of lino, which is 464F.

    Also, plateau is not correct, strictly speaking. A graph generated by cooling linotype will have a descending section as the liquid starts to cool, a flat section as it changes to a solid and a further descending section as it cools to room temperature. I have to emphasize that all this came from the article. I have not done this myself.

    When I mentioned pure lead, I may have been thinking about some information I saved from Bill Ferguson. I have quite a lot of it and it will take me some time to go through it.
    John
    W.TN

  19. #39
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    this is what brings us back day after day great post Gear Please keep us updated and informed
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  20. #40
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    Gear, like others, all I can do is say, ''Thanks.'' It may seem long to you but to alot of us it is short and to the point. We got the info and now to the casting area we go, thanks again, John.

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