MOLDS AND HEAT

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  • Last Post 05 December 2007
CB posted this 28 August 2007

Molds and Heat

I made a picture of how I think the alloy/bullet and mold heat and cool in the casting cycle, while casting “good” bullets.

The alloy in the pot is hot, the mold is empty and cooling.

The pour starts, the alloy in the mold cools as the mold heats up. At some point the bullet and sprue are solid, at some point the mold and the spout are separated. Either can be first.

The bullet in the mold and the mold cool.

The mold is opened, the bullet comes out of the mold.

The mold continues to cool.

The alloy in the pot is hot, the mold is empty and cooling.

And so on.

I'll try to attach the picture.

We go through a lot of gyrations casting bullets.

Sometimes we cool the mold or sprue plate on a wet surface between castings, a la Bruce B or Dick Howes or A.C. Gould. 

Sometimes we cool the mold, empty or full, with a fan.

Sometimes we wait a long time for the mold to cool before opening the sprue plate.

Sometimes we heat the mold on a hot plate.

Sometimes we put the mold in the alloy to heat it up, while casting.

Some of us say the old “Every mold is different, only trial and error will teach you how to cast with a given mold.” The old “there are too many variables to ever understand how it works” business.

I think that there are only two things we can vary in bullet casting, the temperature of the pot and time. Temperature is easy, but time has several components.

Time the spout is in contact with the sprue plate or is keeping a molten puddle of alloy on the sprue plate.

Time between moving the mold from the spout and opening the sprue plate.

Time between removing the bullet and closing the sprue plate and starting the next pour.

Aside from the temperature and time variations are the wet sponge, fan, hot plate businesses.

Time has some value to us, even to old retired guys like me. I'd like to cast good bullets faster, that's what most of the gyrations are about.

The gyrations are necessary because there's an imbalance between the alloy freezing temperature and the mold dimensions.

If the mold is too small, it has to be cooled down.

If the mold is too big, it has to be heated up.

A small mold example is my Ohaus 45-405 mold that casts 45 caliber 433 grain bullets. It is 1” X 1.25” X 1.4” high with a sprue plate 1” tapering to .5” X 1.5".

This mold needs a lot of cooling time.

A big mold example is my custom made 30 caliber mold casting a 185 grain bullet. It is 1.38” X 1.25” X 1.6” high with a sprue plate 1.25” tapering to 1” X 1.86” long. A heavy mold with a big thick sprue plate, it needs the pot running wide open and dipping in the alloy every 2-3 bullets to cast good bullets.

Another big example is the Eagan 58 grain 22 caliber mold, that took a lot opf heat and a lot of time to cast good bullets.

During the casting process molds cool off more than I'd ever expected, from ~500-550F to ~250-350F between solidification and re-pouring. Molds are excellent heat dispersers. Heat dispersion with molds of a given material, iron or brass or aluminum in still air, at room temperature is a function of the total heat in the mold and the surface area of the mold.

If the mold is going to cast a great big bullet, the mold needs to be big.

If the mold is going to cast a small bullet, the mold needs to be small.

Mold size, for maximum casting speed, is a function of  bullet weight, and maybe dimension ratios, but certainly of bullet weight.

This relationship is easily understood, I think, and easy to define.

What's the practical application, you (Pat) ask? If we understand the relationship, we can devise ways to build molds of the proper size, modify existing mold sizes, and/or insulate or enhance surface heat transfer.

I think that a too-big mold can be made smaller with an increase in casting speed.

I think that a too-small mold can be increased in surface area with an increase in casting speed.

Is this wrong? Or, is it time for some experiments?

joe brennan  

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RicinYakima posted this 28 August 2007

Joe,

Here are some thoughts on this subject:

Lyman single cavity moulds seem most efficient with a bullet weight between 170 and 200 grains. Lyman double cavity moulds seem best with a total of 300 to 450 grains of bullets.

You could calculate the total cast iron volume of the mould under water and compare it to the total volume of lead it takes to fill the cavity (..ies). Consider using the volume of the mould handles that touch the mould also.

You would have to do this for each metal that moulds are made of as each has a specific heat to raise or lower one degree, F. Then calculate the BTU's each quantity of lead per bullet yields to the mould and how much that raises the temperature.

You can increase the rate of heat dissipation by painting the outside of the mould body with flat black lacquer (bar-b-que black).

 Ric

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CB posted this 29 August 2007

Joe Brennan wrote: What's the practical application, you (Pat) ask? If we understand the relationship, we can devise ways to build molds of the proper size, modify existing mold sizes, and/or insulate or enhance .

Joe,

Who's the we in “ we can devise ways to build molds of the proper size, modify existing mold sizes, and/or insulate or enhance surface heat transfer"?

 Good luck getting a commercial or custom mould maker to cut caliber specific mould blocks unless you're willing to spend a bushel basket of rubles for a mould. I think changing the outside dimensions of an existing mould would encompass a lot more than just sticking it in a mill and hacking away. Do you have a plan devised for insulating a mould, I'm all ears?

You said.

"Some of us say the old “Every mold is different, only trial and error will teach you how to cast with a given mold.” The old “there are too many variables to ever understand how it works” business."

"A small mold example is my Ohaus 45-405 mold that casts 45 caliber 433 grain bullets. It is 1” X 1.25” X 1.4” high with a sprue plate 1” tapering to .5” X 1.5". This mold needs a lot of cooling time."

"A big mold example is my custom made 30 caliber mold casting a 185 grain bullet. It is 1.38” X 1.25” X 1.6” high with a sprue plate 1.25” tapering to 1” X 1.86” long. A heavy mold with a big thick sprue plate, it needs the pot running wide open and dipping in the alloy every 2-3 bullets to cast good bullets."

"Another big example is the Eagan 58 grain 22 caliber mold, that took a lot of  heat and a lot of time to cast good bullets."

----------------------------

It seems that by trial and error, how much effort is really involved here, you found out how to make all three moulds cast good bullets. It ain't about too many variables to ever be able to understand how it works all I want is for the mould to drop a good bullet and if I have to go through the extra labor of turning the temp control dial up a smidgen or wait the extra second I'll grit my teeth and do the twisting and waiting. What we're doing here is pouring melted lead into a cavity, just like casting tin soldiers but a lot less complicated. What you suggest probably does make some sense but if you're going to start looking for a definite relationship between a moulds physical dimensions and caliber size to use with a set temperature and casting  cadence you better turn off the computer and crack out the lawn mower because you're gonna need the extra dough.

Since it sounds like you have a few moulds that'd be perfect candidates for the milling machine or insulation test once you get the results from casting with a 1/2 x 1/2 inch .22 cal. mould or a mould wrapped in asbestos let me know how well it worked . Me, I'll just stick to turning the heat up a bit or spending the extra 200 seconds it'd take to get 100 good bullets.

I have to say Joe, you're one of, if not the most, intense cast bullet shooters I've ever seen or heard of. You must open your eyes every morning thinking of this stuff to keep the topics coming. You better take a break and get involved in one of the plinking topics before your head explodes or your calculator burns out. :)

Heard anything about your pistol?

Pat

 

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CB posted this 29 August 2007

pat i. wrote: Joe Brennan wrote: What's the practical application, you (Pat) ask? If we understand the relationship, we can devise ways to build molds of the proper size, modify existing mold sizes, and/or insulate or enhance .

Joe,

Who's the we in “ we can devise ways to build molds of the proper size, modify existing mold sizes, and/or insulate or enhance surface heat transfer"?

 Good luck getting a commercial or custom mould maker to cut caliber specific mould blocks unless you're willing to spend a bushel basket of rubles for a mould. I think changing the outside dimensions of an existing mould would encompass a lot more than just sticking it in a mill and hacking away. Do you have a plan devised for insulating a mould, I'm all ears?

You said.

"Some of us say the old “Every mold is different, only trial and error will teach you how to cast with a given mold.” The old “there are too many variables to ever understand how it works” business."

"A small mold example is my Ohaus 45-405 mold that casts 45 caliber 433 grain bullets. It is 1” X 1.25” X 1.4” high with a sprue plate 1” tapering to .5” X 1.5". This mold needs a lot of cooling time."

"A big mold example is my custom made 30 caliber mold casting a 185 grain bullet. It is 1.38” X 1.25” X 1.6” high with a sprue plate 1.25” tapering to 1” X 1.86” long. A heavy mold with a big thick sprue plate, it needs the pot running wide open and dipping in the alloy every 2-3 bullets to cast good bullets."

"Another big example is the Eagan 58 grain 22 caliber mold, that took a lot of  heat and a lot of time to cast good bullets."

----------------------------

It seems that by trial and error, how much effort is really involved here, you found out how to make all three moulds cast good bullets. It ain't about too many variables to ever be able to understand how it works all I want is for the mould to drop a good bullet and if I have to go through the extra labor of turning the temp control dial up a smidgen or wait the extra second I'll grit my teeth and do the twisting and waiting. What we're doing here is pouring melted lead into a cavity, just like casting tin soldiers but a lot less complicated. What you suggest probably does make some sense but if you're going to start looking for a definite relationship between a moulds physical dimensions and caliber size to use with a set temperature and casting  cadence you better turn off the computer and crack out the lawn mower because you're gonna need the extra dough.

Since it sounds like you have a few moulds that'd be perfect candidates for the milling machine or insulation test once you get the results from casting with a 1/2 x 1/2 inch .22 cal. mould or a mould wrapped in asbestos let me know how well it worked . Me, I'll just stick to turning the heat up a bit or spending the extra 200 seconds it'd take to get 100 good bullets.

I have to say Joe, you're one of, if not the most, intense cast bullet shooters I've ever seen or heard of. You must open your eyes every morning thinking of this stuff to keep the topics coming. You better take a break and get involved in one of the plinking topics before your head explodes or your calculator burns out. :)

Heard anything about your pistol?

Pat

 

I'm counting on you to do much of the work on the molds. Perhaps contribute a lot of money to the effort. Immerse yourself in the mold/heat business. Get into it.

I'm still reading responses here and on Cast Boolits. I think, maybe, we can learn something we don't know now about molds and sizes and temperatures.

I ordered the pistol the last Monday in July, delivery to be in 10 weeks. The $100 deposit check has been cashed. I think next Monday is 5 weeks, I'm hoping Thanksgiving and thinking Christmas. I hate to order brass and mold and sizing die and powder and ... this early, but I need to get going and cast bullets, load them in cases and send them off.

I'll be back. Remember those words to guide your life-Molds and Heat!!!

joe brennan  

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CB posted this 30 August 2007

Joe Brennan wrote: pat i. wrote: Joe Brennan wrote:

I'm counting on you to do much of the work on the molds. Perhaps contribute a lot of money to the effort. Immerse yourself in the mold/heat business. Get into it.

Joe,

Being a union man for the majority of my working life I can see you were either a politician, bureaucrat, or middle manager with a lot of ideas but no practical knowledge or intentions of getting your hands dirty in your past life. :)

Pat

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CB posted this 01 September 2007

Hey Joe; Your experiments and the results are welcomed by other casters who may be as anal as yorself. My experience goes back over 45 years and I am learning something every day. Trimming one tenth of an inch off a group when the group is five inches, is easy. Taking a tenth off my group is very tedious and I appreciate any help I can get. Thanks for your information, I expect to investigate how to take advantage of this education. When you come to the Daytona area, come as my guest and shoot Lawnsteel with us. Roy

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CB posted this 02 September 2007

Some molds are “hot", they require some cooling off between pours. We wait for the cooling of, or have a fan blowing on the mold, or use the Bruce B, Dick Howes, A. C. Gould method of cooling the mold on a wet sponge or pad. These molds are too hot. An example is the Ohaus 45-405, a 45 caliber 433 grain SC mold..

Some molds are just right, normal unhurried and un-slowed cycling through the casting operation gives us good bullets, fast.

Some molds are “cold", they require quick casting or dipping the mold in the lead or heating on a hot plate or operating at a high pot temperature or a combination of these or other “fixes". If you stop for a bit you get wrinkled bullets. These molds are too cold. An example is the custom #78-185, a 185 grain 30 caliber SC mold.

I took a sample of molds, only iron/steel molds because I don't want to deal with brass or aluminum now. No Hoch molds because the geometry is so different from Lyman/RCBS/NEI/Ohaus molds.

I measured the length, width and height of the molds.

Sprue plates all covered the mold top, and then hung over some amount. I traced the overhang onto graph paper and used that to estimate the overhang area.

I measured the bullet length, estimated a representative bullet weight, put it all in a spreadsheet, and calculated the mold surface area.

Then calculated bullet grains per square inch of mold surface area.

Then calculated the mold plus overhang surface area; and bullet grains per square inch of that surface area.

The Ohaus mold had the largest number of grains of bullet weight per square inch of mold or mold/sprue area, at 49.71 and 42.65 grains per square inch.

The #78-185 mold had the smallest number of grains of bullet weight per square inch of mold or mold/sprue area, at 15.56 and 12.73 grains per square inch.

The Ohaus mold is too hot because it has too much lead going into too small a mold.

The #78-185 mold is too cold because it has too much surface area on the mold and sprue plate for the size of the bullet.

I've attached the WORD copy of this with the table. I'm looking for data on iron molds for both smaller and larger than 30 calibers. Or any caliber, including light 30s.

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RicinYakima posted this 02 September 2007

How fortuitously timed Joe!

I was casting some bullets for a new 45/70 today, and used probably the largest bullet made in the Ideal small blocks..

Ideal 457191: blocks were 1.1 x 1.19 x 1.36 inches, with an area of 8.3876 in sq.

Bullet is 292 grains when made from 25/1 lead to tin alloy and the bullet is 0.790 inches long.

Grains per in sq. would be 34.8133

With sprue cutter area would 33.4955 grains per in sq.

Normally I cast in the winter with a shop temperature of about 35 degrees F. I can rest the moulds on a plate of Al while the sprue hardens and cast at 670 degrees at my normal pace.

Today it was 85 degrees in the shop (very unpleasant!) and cast at the lowest possible temperature, 655 degrees. I had to put four thicknesses of toweling, damp, on the Al plate and cast at about 2/3 my normal rate to keep from over heating the mould.

Hope this is some use to you.

Ric

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CB posted this 03 September 2007

RicinYakima wrote: How fortuitously timed Joe!

I was casting some bullets for a new 45/70 today, and used probably the largest bullet made in the Ideal small blocks..

Ideal 457191: blocks were 1.1 x 1.19 x 1.36 inches, with an area of 8.3876 in sq.

Bullet is 292 grains when made from 25/1 lead to tin alloy and the bullet is 0.790 inches long.

Grains per in sq. would be 34.8133

With sprue cutter area would 33.4955 grains per in sq.

Normally I cast in the winter with a shop temperature of about 35 degrees F. I can rest the moulds on a plate of Al while the sprue hardens and cast at 670 degrees at my normal pace.

Today it was 85 degrees in the shop (very unpleasant!) and cast at the lowest possible temperature, 655 degrees. I had to put four thicknesses of toweling, damp, on the Al plate and cast at about 2/3 my normal rate to keep from over heating the mould.

Hope this is some use to you.

Ric

Ric;

First, I'm surprised at the 1.1” length, parallel to the handles. My Lyman molds measure ~1” long SC and ~1.23” long DC. Would you check that please?

Then, without the sprue plate I get 33 grains per square inch, on the high side. I just made a forecast on Cast Boolits at 34, that the mold will cycle slower than you want, but won't be as horrible as my 45-405 at ~50. From your description, that's about where you are. This is a hot mold.

This thing is a lot easier than I ever thought. I do love them stats!! Here's he updated .XLS file.

joe brennan

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CB posted this 03 September 2007

Lyman molds are about 1” long SC and 1.23” long DC, parallel to the handles; 1.2” wide SC and 1.385” wide DC, and 1.37” high SC and 1.48” high DC.

The 314299 mold, sort of new, has a .182” thick sprue plate, all others 1/8” thick. This is a hot mold, at ~ 37 grains per square inch.

All Lyman sprue plates cover the mold top and then have an overhang. This overhang size and shape is the same for SC and DC molds, of widely varying vintages. The SC overhang is ~.75", the DC overhang is ~.1".

Does anyone have different measurements?

Need measurements and comments on RCBS molds.

Thanks;

joe brennan

 

 

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CB posted this 03 September 2007

gunarea wrote: Hey Joe; Your experiments and the results are welcomed by other casters who may be as anal as yorself. My experience goes back over 45 years and I am learning something every day. Trimming one tenth of an inch off a group when the group is five inches, is easy. Taking a tenth off my group is very tedious and I appreciate any help I can get. Thanks for your information, I expect to investigate how to take advantage of this education. When you come to the Daytona area, come as my guest and shoot Lawnsteel with us. Roy Thanks, Roy. I knew that those other guys were just kidding. Even if they're wrong.

Whenever we go to the Orlando area, I'll send you a message.

joe brennan

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RicinYakima posted this 03 September 2007

Joe,

I read the first measurements off a scale (which I must have not done well!). Here they are with a dial micometer: width is 1.189 inches, depth is 0.980 and height is 1.355. Hope it didn't mess up your data base. Humbly, Ric  :?

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CB posted this 04 September 2007

RicinYakima wrote: Joe,

I read the first measurements off a scale (which I must have not done well!). Here they are with a dial micometer: width is 1.189 inches, depth is 0.980 and height is 1.355. Hope it didn't mess up your data base. Humbly, Ric  :? Ric; These are the standard SC Lyman dimensions. I'm assuming that the sprue plate overhangs ~.75", and updated the spreadsheet.

Do you have any RCBS mold dimensions?

Thanks;

joe brennan

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RicinYakima posted this 04 September 2007

Joe,

I have a lot of moulds, Cramer, Lachmiller, Hensley & Gibs, Ohaus and RCBS in iron. Do you want a list of them all? I also have casting notes on most of them. I'm pretty well booked this week, but could get them the coming weekend.

Ric

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CB posted this 04 September 2007

Ric;

Yes, I'd like all the data I can get. Dimensions of the molds less the sprue plate, bullet weight, and about the sprue size.

Specially looking for small = 22 or 24 caliber molds, and big = 40 0r 44 or 45 caliber molds.

A few to start would be appreciated, don't go to a lot of trouble.

If you want, let me be Kreskin. You tell me the dimensions of the mold and the bullet weight, and I'll tell you if the mold is “hot” or “cold".

or

You tell me about a “hot” or “cold” mold, and I'll tell you the square inches of mold surface.

Is this possible? I think so, even with the small sample I've got so far.

Thanks;

joe brennan

 

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RicinYakima posted this 07 September 2007

More mould dimensions you requested.

1. SAECO, three cavity for 158 grain 38 SWC's. Width 1.32/depth 1.77/ height 1.50. Plate is .20 thick and has 0.942 in squared knockoff lever.

2 Hensley and Gibbs two cavity for 170 grains 30 cal flat nose. Width is 1.25/depth 1.58/height is 1.52. Plate is 0.19 thick and has 0.48 in squared knockoff lever.

3 NEI (iron), one cavity 30 caliber 188 grains round nose. Width is 1.23/depth is 1.75/height is 1.50. Plate is 0.19 thick and has 1.09 in squared knockoff lever.

4 Cramer, 2 cavity 44 caliber 250 grain SWC. Width is 1.31/ depth is 1.75/height is 1.50. Plate is .20 thick and has 0.940 in squared of knockoff lever.

I checked them with a dial caliper this time. They are correct.  Ric

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John Boy posted this 07 September 2007

Why hasn't there been any mention in this thread of The 8-Phase Casting Cycle? http://www.longrangebpcr.com/Part1.htm>http://www.longrangebpcr.com/Part1.htm

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billwnr posted this 07 September 2007

John Boy wrote: Why hasn't there been any mention in this thread of The 8-Phase Casting Cycle? http://www.longrangebpcr.com/Part1.htm>http://www.longrangebpcr.com/Part1.htm Hmmmm... this article says the hotter the mould the heavier the bullet.

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RicinYakima posted this 08 September 2007

However, this is intended for lead / tin alloys. These are true solutions. There is no discussion of bi-metallic tin / antimony and free antimony crystal alloys that are the basis of WW alloys that most of us use. I don't think there is any disagreement that lead / tin alloys will make bigger and heavier bullets the hotter the mould. Ric

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billwnr posted this 08 September 2007

I must have read one of the earlier posts wrong. I thought it was stated the hotter the mould the lighter the bullet as the expansion of the mould gave less area for the alloy to fill.

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CB posted this 08 September 2007

RicinYakima wrote: However, this is intended for lead / tin alloys. These are true solutions. There is no discussion of bi-metallic tin / antimony and free antimony crystal alloys that are the basis of WW alloys that most of us use. I don't think there is any disagreement that lead / tin alloys will make bigger and heavier bullets the hotter the mould. Ric I disagree. Any alloy freezes at a certain temperature, no matter what temperature the pot of alloy is at, no matter what temperature the mold is at. (We're talking about while casting good bullets.)

Then I see the pour, the mold heat up as the alloy gives heat to the mold, mold and alloy reaching the freeze or begin-to-be-slushy point, and so on. Thus, I think neither mold nor alloy temp affects bullet size or weight, for any given alloy.

I think.

joe brennan

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