mold temp/boolit size

[onesonek]

I'm curious, and just wanted to touch bases on these quotes, so I C&P'd them from the S&S forum. I think it warrents further discussion in the CB forum.


I don't understand your response. Neither frosty nor shiny. You mean satin? I've found that a lightly frosted boolit in .35 caliber almost always is .001" smaller than a bright, shiny one from WW metal. I usually run aluminum moulds hot enough with WW metal to get a light, satin frost that will wipe right off with a dry rag. My point is that if you already cast at this temperature, the mould is a tad bigger than I would like, but if you cast with the mould cool enough for shiny boolits, it will probably cast .359" for me, which is more to my liking. How about pics of mould and boolits? This is a serious inquiry, but if it isn't just what I want I can order a brand-new one made to my specs for a few dollars more.

Gear

I found similar results,,,,I think frosted shrink more. But I'm guessing?????
Although my findings came from a brass mold. So that's a different factor, to a point.



that doesn't make any sense
you are telling me I can change the dimensions of a mold by the temp I cast
I say you are wrong :confused:
maybe one casting but to physically change the internal dimensions ain't gunna happen

Changing mold temp. will change dia. up to a point,,,physics in action!


Your mold metal expands with heat. Of the three metals commonly used, iron brass and aluminum, aluminum expands the most.

When calculating the cavity diameter needed to produce a given bullet diameter with a given alloy, about .002", depending on bullet size, must be subtracted when making a mold from aluminum. Even then, the hotter you keep the mold when casting, the larger the bullet.

While I understand this is physics in action, and can't argue it, I have seen where boolit's from a hotter mold throwing lightly frosted, are smaller than cooler mold (shiney boolits) also. Albeit, in my findings, they came from a Brass mold rather than Alum. It goes against the heat/expansion physics,,,,but is the alloy shrinking more then the expansion properties of mold? Or is it by fluctuations of pot/alloy temp causing this?
I found the same thing as Gear did, same alloy with different casting cadence, making for hotter mold. Although I can't say that I had the alloy the same temp.. It may have had slightly hotter or cooler, but no more than 20 degrees, either side of 670*. Also, there was 20* difference in ambient air temp. for these aircooled results,,,,any effect there?

[geargnasher]

There is indeed no arguing with the laws of physics, only disagreements about observations of them.

Hotter alloy has more VOLUME than cooler alloy, so it shrinks more when cooled. If poured into the same sized cavity, the hotter alloy will produce a lighter and smaller boolit.

Now, for mould temperature. I've found that the frostier the boolit, (hotter the mould), the smaller the boolit. One assumption is that as the mould blocks expand, the cavities become smaller, as air space is displaced by expanding metal, but sometimes the opposite happens. Depends a lot on the mould material and the shape of the cavities. My experience mirrors Tom's, to a point. We can agree that aluminum moulds expand more per given temperature (thermal expansion rate), but even with aluminum you get to a certain point where as the mould gets hotter, the boolits get smaller if the alloy contains a significant amount of antimony, like wheel weight metal, Lyman #2, or some of the type metals. This may not be observed by most people because they never get the mould hot enough to tell, or use low-antimony alloy. The boolits usually will start small at the minimum mould temp, then get larger as the mould continues to expand with heat, but once light frosting starts to happen, the boolits begin to SHRINK. This is a property of the boolit metal, NOT the mould blocks.

Another point of interest here is that while iron, steel, free-machining brass, and most machine or aircraft grades of aluminum alloy have different thermal expansion rates, they do not have the same coefficient of heat. Brass transmits heat about three times better than aluminum, but doesn't expand as much overall for the same BTU uptake.

White Eagle, I have to tell you, before you go stating facts you should really verify them first, because your statement quoted above is very wrong.

Gear

[felix]

Excellent again, Gear! ... felix

[GaryN]

I'm sure glad we have a few guys around here that not only know what they are talking about but are willing to share it with us. I am always learning things on this site. I thought I knew a lot about casting. I have been learned that I don't. Thanks guys. Please keep posting.

[white eagle]

first off you said I made the mold cavs. bigger by cast hot
or what ever temp
I called that bs
your way of thinking is by the time you cast ten times time to junk the mold because its now .010 out of spec .
I agreed from the get go on fluctuations in size maybe you had better be clearer on what it is you are try to say before you ruin my post
and I do believe you trashed the thread with your question

[onesonek]

Thanks Gear,,,That confirms my thoughts, and answers my questions. I personally don't have the experience or depth of knowledge, in cast boolits or metalurgy, and really appreciate those that do, as Gary said. I didn't question Tom's post one bit, just wanted some answers, to what was was happeing. I could have researched it on the net, and eventually found all I wanted. But it sometimes saves tons of time in those searches, by asking here, of those that have been at it longer and or know, or both. And like times before, I appreciate your's and other's patience and time, with me and those like me in answering our questions.

[onesonek]

first off you said I made the mold cavs. bigger by cast hot
or what ever temp
I called that bs
your way of thinking is by the time you cast ten times time to junk the mold because its now .010 out of spec .
I agreed from the get go on fluctuations in size maybe you had better be clearer on what it is you are try to say before you ruin my post
and I do believe you trashed the thread with your question

I didn't take Gear's response's as trashing at all white eagle. I took it as simple questions, more investigative in nature. Wondering more so, at how you are running your mold. I took it as, if you ran it the same as him roughly, and the mold was throwing .360", then the mold would be throwing too large by .001" for his liking is all. He did not say anything that could be construed as ruining the mold, as far as I could see. I see it where you took the offensive here,,,maybe, by not understanding what he was asking???

[Von Gruff]

On subject but with qualifications. But first to diverge to another posting that suguested cool alloy and hot mould and as I had previously been casting with medium hot alloy (no temp guage) and cooler mould and while I got good boolits they always needed a bit of persuasion to leave the mould. I tried the cool alloy and hot mould and got bigger boolits by .0005 noticable on the nose when they were nose sized. They did drop more freely from the mould though so I tried med hot alloy as I previously used and a hot mould and have free droping boolit without the larger dia. Win win for me but it did show me that I can get differing sized boolits from my (Lyman) mould depending on heat of both mould and alloy.

Von Gruff.

[357shooter]

Casting with a hot mould, at least with cavity sizes for 158-180 grain 357's does drop a larger diameter bullet. Having the temp just shy of frosting, and keeping it there works the best.

I get the biggest out of my moulds by also casting with a hot alloy. Preferably over 850 degrees, for the best results. Most of the alloy is soft-binary, about BHN7. However it also works well with WW. For the Keith style and SWC style bullets in the weight range mentioned, cool alloy doesn't work. Not for my bullets.

The bullets in my avatar were cast with a 420 degree aluminum mould and 900 degree binary alloy. I've cast WW using the same temps with the same full-size diameter results.

Regarding moulds with the cavity size mentioned produced these results in the link below:

http://357shooter.blogspot.com/2011/02/extensive-mould-mould-temperature-test.html

[leftiye]

+1 on the hotter mold being bigger. It's like heating a ring of metal, it expands all around and the center diameter gets bigger.

+1 on biggest boolits happening at just before frosting. Hotter than this and the whole boolit shrinks rather than freezing to the mold and then drawing metal in from the sprue. This doesn't happen all at once, the hotter the mold the more this is the case.

[geargnasher]

First off, W.E., Onesonoak understood exactly what I was asking in the other thread, I don't know why you STILL don't, but it's moot. I wasn't "trashing" anything, and in fact took your rude "yaking" comment in stride.

Von Gruff, you and I have similar experiences, it has to do with balancing the heat of the mould and the alloy to get what you want. At a certain point, antimonial alloys start shrinking more upon cooling, while the mould continues to grow in a fairly linear fashion with increasing temps. A graph of mould temp vs. cavity size in many moulds is a sloped line, whereas WW alloy is a curve up and back down again, with the peak being somewhere around the lower end of slight frost, or maybe just above the top end of the shiny spectrum. Notice I said MOULD temp, not ALLOY temp. Hotter alloy shrinks more upon cooling and aids dropout, but it's MOULD temperature that creates frost and the factor of smaller FINAL diameter of COOLED boolits above the beginning of the frosty point.

.357Shooter, if you're casting WW at 900 degrees, all bets are off since you are off the charts. You destroy any positive effect of tin, and I don't really know what antimony does at that temperature. Your mould temperature is more than hot enough to make frosty antimonial boolits regardless of alloy temperature, so you should be getting smaller boolits, but with alloy that hot who knows. Hotter alloy will usually make smaller boolits at ANY given mould temperature, but a hotter mould will make bigger boolits up to a point, then smaller ones if using antimonial alloy. With binary lead/tin alloy, there is no "hump" in the curve, the mould temperature and boolit size increase to the top of the useful casting range. I try to figure what the other person is doing that makes the results different, when differences arise. I think Tom at Accurate moulds is a "shiny" caster, as is Swede Nelson and many others, and this influences greatly the moulds and specs they produce for someone like me who casts a WW type alloy typically and enjoy satin boolits. And I have to say it one more time, "if cooler alloy doesn't work. Not for my bullets" then either your thermometer is out of calibration, or you live on a different planet than I do, because it WILL work. Not saying your should at all, do what works for you with your tools and metals, but don't assume that it's true for the rest of us who use different alloy with different contaminants and different equipment/technique. If the alloy is hot enough to pour, it will make fine boolits if your mould is at the correct temperature and you don't have contaminants like zink or aluminum in there. In my experience, the closer you get to pure lead, the hotter the mould needs to be, and also the alloy, up to the point at which tin becomes impotent to prevent the lead surface from flash-oxidizing and filling poorly, which occurs above 750-ish degrees.

To each their own, with mould temperature and frosty/shiny, I say that a lot, because it really is up to the individual's preference, and the gun usually doesn't care as long as the final product FITS. But if you've never measured a frosty boolit and compared it to a shiny, wrinkled, cull cast from same alloy, same session, same alloy temperature, you're missing something important.

Gear

[357shooter]

Gear: Maybe some day we'll figure out why we get different results.

As far as the tin and antimony goes in WW, I did try to cook it out, on purpose. After a few hours at 900-950 degrees there was no affect. Had to resort to annealing the WW bullets to get them softer.

[geargnasher]

Gear: Maybe some day we'll figure out why we get different results.

As far as the tin and antimony goes in WW, I did try to cook it out, on purpose. After a few hours at 900-950 degrees there was no affect. Had to resort to annealing the WW bullets to get them softer.

If we ever get the chance to get together sometime, I'll buy the coffee! It would be fun to compare thermometer readings and alloys side-by-side. Just removing a portion of the tin won't make a very significant difference in hardness of WW type alloys anyway, so that's probably why you didn't notice any practial difference, and if you're not skimming or disturbing the surface every few minutes the oxidation will stabilize at a certain point. Tin does two things for us: It toughens the alloy slightly by itself, it makes really tough alloy when combined with antimony to make the intermetallic Sb/Sn, and it provides an oxide shield to the surface of molten lead which makes the lead flow better, or "wetter" to use a soldering term. The effect of lost tin on boolit fillout quality is realized at much lower temperatures than you've been casting, like around 650-700 degrees. Above 750-800 degrees it's difficult to tell from looking or casting quality whether there is any tin in there or not.

Gear

[RobS]

Another good thread.

Gear:

I have a particular 4 cavity HP mold that needs hot alloy because I simply can't run enough cycles through it to keep it up to temp any other way. Huge HP pins, heavy HP pin hardware and the combination of a square lube groove are contributors. Keeping the mold up to temp can be very difficult to say the least and boolits can become a real PITA to drop when the mold is too cool which makes the entire problem worse as it takes longer to get the mold to drop boolits.

Partly because I’m a cheap caster, this mold I use for my 45 ACP and 454 Casull varmit loads usually sees 50/50 WW to lead or maybe a touch more lead in the mix for a softer alloy. Because of the hot temps I have to cast at (900 degrees) with this mold air cooled WW/Pb is a good alloy for the HP configuration. Burning off tin really isn't a big concern since there is only about a 1/2 percent or possibly even less depending on the amount of Pb added to the WW alloy. A very thin layer forms on the top while casting but I don't skim it. This small amount of dross doesn't seem to affect the outcome of the boolits (weight/diameter) whether they are from the start of the pot or from the end. I can't tell you what will happen to the alloy if I left it for hours but it doesn't take me very long to run a 20 pound pot with a 4 cavity mold.

If I do decide on a lead/tin binary alloy then I dump on the saw dust a good 3/4-1" thick to cut down on oxidation. When I run toward the bottom of the pot there is only ash left on top of the 1/2" lead left in the bottom. Doing this I've kept consistency from the first boolit to the last.

Elements can oxidize out of an alloy at higher temps but pot run-out time, if kept reasonable or not longer than necessary, helps it would seem and using an oxygen buffer/barrier can help a great deal as well. If I was going to cast at a high temp regardless of alloy I mentioned with a small caliber 2 cavity mold then I would layer on the sawdust, especially if a lead-tin alloy, or only make half pots of alloy to shorten the time the alloy is in the pot.

[geargnasher]

Exactly, Rob. I made these points a while back on 357Shooter's alloy temp thread. I cast HPs with very similar alloy, 50/50 WW/pure, no added tin, and high pot temps. Layer of sawdust smoldering on top keeps the alloy consistent, but the only reason I care about the tin at hight temps is that there is enough there to blend a little with the antimony. I really like that alloy for HP pistol boolits, outstanding expansion even well under 1000 fps.

Gear

[357shooter]

Gear: I'm up for the coffee. The three measures I use to determine that there's no negative impact from casting soft lead, or WW hot are:

1) No difference in the hardness tester (it can't tell a difference)
2) No difference in how they shoot (the gun can't tell)
3) No difference in the target (it can't tell either, the results are equal)

Beyond that, any changes in the alloy makes no difference to me.

You are right on the money in that I don't flux often and don't skim often. No more than 2 times per 15lbs, when casting bullets. I use paraffin for a light flux when casting.

Now smelting, that's another story. The lead gets crazy-fluxed with sawdust.

TTYL

[milprileb]

Gear,

I got to post a new thread on temps and ask your input . Don;t want to divert focus of this thread

[Mal Paso]

I think Aluminum Molds are very different from Brass and Iron. I think Aluminum will expand enough to change boolit size. I did the math once on Iron and there isn't enough expansion to consider.

The bottom pour 20# Lee is a different critter too. How it heats and how much the spout/lead stream cools the Alloy. My first casting sessions it was all I could do to keep the spout from freezing at the temperatures I was given. It says 760 on my Lyman Lead thermometer when all is right with the world. 95/3/2, Lee 20# bottom pour.

I run 2 Brass 4 cavity molds now. My perfect boolit is Just Frosty. The shiny ones are under size and will often have defects. The molds are preheated and are returned to the hot plate whenever there is a pause. I water drop.

I have only cast 1 boolit, the 429421, but I've cast well over 20,000 of them. I started with 1 then 2 Lyman molds but as I changed from Lyman#2 to WW Alloy the boolits went from small to TOO Small. I snagged one of the NOE Group Buy molds and finally had a boolit that fit. I diamond lapped one of the Lyman's and for a while I was running that Lyman alongside the NOE. Of the two the Aluminum NOE was much more forgiving than the Lyman Iron mold so the Lyman set the pace. Now that I think of it there was a comparatively large variation in size in those NOE Boolits but since I was oversize I wasn't concerned. However from Lead Spring Back/Sizer Die Expansion there was a greater variation in finished size. Then I got one of Miha's Group Buy H&G 503s, cast it a couple times, realized how stupid I was, and bought a second mold. Two molds gives me a better boolit and it's much easier on the mold. That 250 grain boolit needs a certain amount of mold time or I get dings, separations, or lead smears and buildup.

Great discussion and I've gotten a few New ideas for my next casting session.

Oh, and thanks for All the Help:castmine:

[geargnasher]

You are correct, Mal Paso, aluminum has a MUCH greater coefficient of thermal expansion than does brass or iron-ish moulds, but brass and iron will start to drop smaller boolits the hotter they get above the end of the shiny phase with antimonial alloys usually with a touch of arsenic, does this matter???), and while I don't fully understand why this happens, I know it does, and figure it has something to do with the metallic grain structure as the alloy cools.

Anybody ever notice that an alloy with any significant amount of grain refiner in it like arsenic or copper casts smaller boolits from a hottter mould compared to, say, linotype, certified Lyman #2, or binary lead/tin alloy?

On the subject of casting temp, I cast a run of Lee 312-180-rn's the other day from certified 93.75Pb, 4Sb, 2Sn, .25As and ran my Pro 4-20 at 635 on my PID controller. Zero freeze-ups, and I have peened my spout and redrilled for a smaller hole. I don't know what the difference is between our situations, unless it was especially cool where you live or you had a fan blowing on your pot. Casting at four pours a minute the boolits were lightly frosted and perfectly filled, only about two percent culls from the water bucket (mostly band dings). I must have the best Lee pot ever made, because once I learned how to keep it clean and tuned-up, it doesn't drip, freeze, or give me problems at all.

Gear

[gray wolf]

I must have the best Lee pot ever made, because once I learned how to keep it clean and tuned-up, it doesn't drip, freeze, or give me problems at all.

My Lee pot ( 20# B/P ) is relatively new, 6 Mo. old--I use nothing but saw dust for flux,
wooden stick and an old spoon to stir. It didn't leak at the start and does not leak or drip now. I oil everything that moves and keep it as clean as possible.
My alloy is basically WW Range scrap mix. Slush at 450-475* Fluid at 550*
I have been able to cast very nice bullets at 625*---675* depending on the mold.
My spout will freeze at 600* I can get it to flow with a little help from my torch and it is fine after 620* or so.
If I get tired and slow down a little I can pour a little bigger sprue or go up 50* in temp.
I don't see how someone can have a mold up to temp--do 4 pours a min. with supper heated alloy. If I tried that I would have to Waite forever for my sprue to solidify.
I guess I should say: this is with all the other variables staying within an acceptable range.
I am always willing to try different things, I am not the type of person that will say,
I always did it that way--so why change.
BUT--to avoid the fiery slings and arrows I have to say it it works for you--fine--
My problem ( yes I do have them ) seems to come up when a mold is made to a specific alloy with critical dimensions.
I don't mind a .001 or so over sized, I like .002 over if I can get it.
I can't afford Lino or tin, so if it won't work with WW--or WW/pure or range scrap I have serious problems, which in turn causes the level of drama to increase as I cast.

[ColColt]

I can't afford Lino or tin, so if it won't work with WW--or WW/pure or range scrap I have serious problems, which in turn causes the level of drama to increase as I cast.

Time was when LT was a decent price. The last I bought was .25/lb(or less) but that was long ago. I bought enough that I still have about 40 pounds even though the original purchase was around 1972.

If you want to try a mix using LT, ebay has it fairly cheap considering today's prices-when you can find it. You don't know how many times it's been used/melted and fluxed but some of it looks a lot like what I bought decades ago. My next batch of LT when I run out will probably be from RotoMetals. That way I'll know it's fresh and not worked to death.

[ddixie884]

Has anyone had the experience of having WW alloy bullets cast very hot, becoming brittle, to the point of actually breaking at the grooves?

[nanuk]

this site is on the edge of New Thinking all the time.

old myths and wives tales and being debunked routinely.

Casting Technology is increasing in complexity, but also in effectiveness.

Here is a thought that some of you experienced, and well set up casters may consider. and Perhaps get published on Castpics:
Now that MouldMaker/Sponsors and others are making different materials available for moulds,
and alloys are being developed that are pretty consistant, or tested (Rotometals)
And thermometer technology has advanced to the point where one can have a consistant mould temp, and a PID controlled pot can give consistant alloy temps......

some so set up, could TEST with accuracy, and repeatabilitiy, this very subject. Change mould temps, change alloy temps, change alloys, change mould material.... Test the effects on/with each and post a summary.

I would volunteer, but I don't have ANY of that stuff.
I just really enjoy Reading about it. and if I can, I will incorporate what I can into my casting

[smilie=p:

:CastBoolitsisbest:

:coffeecom

[geargnasher]

Nanuk, boolit casting isn't any more complex than it ever was, except the science of metallurgy and alloys gives us greater options as far as manipulating hardness, toughness, malleability, strength, resiliency, elastic limit, and most importantly, grain structure (which is the controlling factor in all of the above). It's still all about melt lead, pour lead, cut sprue, dump boolits, close sprue plate, repeat. The how varies a great deal. Understanding that "how" is a bigger challenge.

The more I learn about this, the more I learn it is extremely difficult to quantify things exactly, because there are so many variables to each caster's knowlege, methods, and equipment. Even the weather is a factor. We have arguments here about whether boolits even change size based upon mould or alloy temp, or alloy composition, because it really is a matter of belief and lack of scientific testing. If you don't believe it makes a difference, and you're only measuring things to the nearest thousandth anyway, then you might never see what I'm talking about. But it DOES matter how big your boolits cast when you're fitting the nose of a bore-rider to about .0002" and another tenth makes it really hard to chamber.

Gear

[Von Gruff]

Here is a way arround bore riders that I have posted before but it may bear a repeat screaning. It is simply an unused sizing die that I have had altered to except Wilson and Redding neck sizing bushes. For my purpose the one I selected in this instance allows me size enough on the nose for interference fit in the bore to seat long (two drive bands held in the neck sized portion of the cartridge) The boolit drops from the mould with the nose .ooo5 over bore size and by sizing just enough of the length I can chamber with nose introduced into bore for accuracy. If I dont get the heat of the alloy and mould right there is too much sizing of the nose and accuracy deteriates. You can just see the minimal sizing indicated by the small screwdriver in the pic.

http://i667.photobucket.com/albums/vv39/VonGruff/002-1.jpg

Von Gruff.

[geargnasher]

Neat trick with the neck-sizer bushings, Von Gruff. Not having any precision machining equipment at my disposal has had me rumaging through boxes of spare parts and dies trying to find "the" part that will work or can be modified to work for sizing noses, if necessary. I made a nose-sizer out of a modified Swedish Mauser sizing die for my .30-06, post sizing about .002" after loading and crimping. A Lee .44 Magnum carbide sizing die and brass rod (for an ejector) works great for uniforming the noses of the 500-grain 458" Lyman boolit in my Shiloh 45-2.4, the Cruise Missile can benefit from a nose-first sizing to the second band in a Lyman H&I set, the list goes on. I'm glad that Yankee ingenuity isn't confined to my continent!

Gear

[Dannix]

Looks like the mould temp sweet spot is very nailed down and quantified. What about for brass moulds though?


Now I know the perfect temperature for a 358-429 aluminum mould
http://357shooter.blogspot.com/2011/02/extensive-mould-mould-temperature-test.html

Cast until I got complete fill out, very shiny bullets and noted the temperature – 315 to 320 deg.
Bullets started to get frosty at 390 and is well on its way at 410deg.
http://castboolits.gunloads.com/showthread.php?t=97835