Casting round balls, how to get the air out?

[David R. Pennington]

Tried running some .595 round balls with new bag mould and can't seem to get them without air pockets. Only about one out of 10 comes out full weight. I can see a tiny air hole in the sprue of most of them. What am I doing wrong? I don't have an electric pot just an old cast iron pot and ladle. Am I too hot or too cold or too fast or too slow? I'm lost. I never had this much trouble pouring smaller size round balls. Most of my .490s come out ok with only a small percentage of culls to go back in pot.

[volatpluvia]

I had the same problem with .590s and a bag mold.  I don't have any idea if the bag mold had anything to do with it, but maybe the size of the ball.  I never cast any other size so I can't say but it seems reasonable that it might be harder to get a bigger ball to cast as well as a smaller ball.  If I kept pouring after the mold was full it seemed to help, in that I got balls without airholes.  I was never into extreme accuracy, and they shot well enough for what I wanted to do so I shot them airholes and all.  They make silhouette go down no matter where you hit it or what the yardage is.
volatpluvia

[smylee grouch]

Could that bag mould be cooling off too quickly? As the last post did, keep pouring after the mold is full and it wont cool off quite as quickly. Just a thought.   Smylee

[David R. Pennington]

That is possible there is not much meat around those molds like a block mold but I don't know how I would keep it any hotter. I was pouring directly over the pot just above the surface of the molten lead, unless my lead was too cold to start with?

[Daryl]

Improper venting from the bag mould. Try pouring only through only one side of the sprue hole, leaving 1/2 the hole open, so the swirrling lead into the mould allows the air to vent as it fills.
The other method is to use a fine file (or if you're dextrous wiht a light hammer and a sharp knife, file or cut very small, narrow air passage lines or grooves on the side of the mould blocks to allow air out as the lead fills the mould.

Either method will work. Look at a modern mould and see the vent lines. The Tanner moulds don't have vent lines, but do have a generous sprue hole, that allows air out as the lead fills the mould.

Lyman, RCBS, Rapine and all other well made moulds have vent lines to allow trapped air out for perfect casts.

I stopped weighing balls for perfect weights many years ago. I preheat my mould blocks, get the lead to proper casting heat and then the first through 100th or 200th balls cast, are perfect. 

[Dave R]

Dave R

I believe Volatpluvia and Smylee hit on something! I learned years ago you must keep pouring the lead after the mold is full with an air gap between the mold and the laddle thus forcing the air out of the mold before the lead hardens!

Dave R

[Kermit]

I've got an old Dixie brass bag mold in .595 and have no trouble. I got pointers from an older and more experienced caster about 4 decades back. He showed me how, with a bottom pour pot or an Ideal dipper (kind that looks like 3/4 of a ball with a little spout on the side), to keep the mold in contact with the ladle or open spout while the ball cools and contracts. As it contracts it continues to pull lead into the mold instead of air. I VERY rarely have trouble casting anything using this method.

[Chris Treichel]

I think your mold might not be hot enough... I usually dip a corner of the mold into the molen lead for a 10 second count (per the instructions that came with the mould) then immediately pour the lead and keep making balls at a good pace to keep the mould hot.  My steel bag mould (.530) works well this way but my Lee mold (.60) with the attached sprue cutter and aluminium block does not work as well when the sprue cutter is closed... so I leave it open and cut off the sprue with wire snip for those balls. I also do my casting when I am out at camp over a fire. andken the inside of the mold with candle soot before starting casting.

[David R. Pennington]

I had thought about opening up the size of the sprue hole a little since it seems very small. It is hard to get the lead in a small enough trickle to not fill all the space in the hole while pouring. I'm not sure I understand about where the "ventlines" should be. Would these be small v slots filed into the side of the sprue hole? I am intrigued about the technique to keep the ladle in contact and let the cooling mold pull lead out of the ladle.
Thanks for the input.  I will try again.

[doug]

   pure lead shrinks tremendously as it cools and becomes solid.  If the amount of lead contained in the sprue and the puddle above it is too small, that shrinkage means that a cavity will be sucked into the ball itself.  My electric lead pot has a deep cavity in it when it cools.   

    I think you have two options; one is to find a way of leaving more lead on top of the bag mold, to accomodate the shrinkage or alternately add a small amount of alloy to the pure lead, which greatly reduces the shrinkage

cheers Doug

[Daryl]

David - look at the touching sides of a normal iron block mould - you will see vent lines running from the cavity to the outside of the blocks- on both halves.  Some guys merely scratch the surface of the bag-mould blocks (sides) across where they fit together. It's easy to get too big a slot with filing if you aren't careful. Air doesn't need much spaces to escape and several tiny grooves on each side of the mould might be all that's necessary.  It's a pain to cast and have to re-melt those balls and try again.  It's best to do it right the first time. I know having a bag mould is the 'in' thing to do, but I prefer quality moulds and balls  and that means a Lee mould at least and usually iron blocks - RCBS, Rapine or Lyman, or Tanner.

Doug's suggestion on the addition of an alloy (antimony or tin, preferrable tin) will work fine as long as the ball is undersized enough to your bore size.

If the lead shrinks down into the ball as it cools, you need to keep the ladle close to add lead to the shrinking puddle on the top surface of the blocks.

[doug]

Doug's suggestion on the addition of an alloy (antimony or tin, preferrable tin) will work fine as long as the ball is undersized enough to your bore size.

    It would not surprise me if you found balls cast with 5% antimony or tin or a mixture of the same, were .002 or .003" larger than those of pure lead

cheers Doug

[David R. Pennington]

Well again it wasn't the brushes fault it was the painter. I tried again this evening and got perfect casts almost every pour. I think I only had 2 culls out 75 balls. Part of my problem was I was pouring too hot. I tried a lower temp. Canted the mold a little and poured very slowly and held the ladle at the mold for a while as the mold cooled and allowed it to syphon more lead in as it cooled. I gave the mold about 3 seconds to cool before opening and that did it. I didn't realize how much thes big diameter balls shrink as they cool.
Thanks for all the input. Problem solved!

[heelerau]

Dave R

I believe Volatpluvia and Smylee hit on something! I learned years ago you must keep pouring the lead after the mold is full with an air gap between the mold and the laddle thus forcing the air out of the mold before the lead hardens!

Dave R 


 I have found the same, keep some lead running over the mould for a few moments longer than you would normally.  With cast block moulds with the flat sprue plate I allways leave a puddle of lead so when it cools you don't see a well appear down the sprue, also make sure the moulds are really hot, awkward with a bag mould but I use a heavy leather glove on the rare occasion I use one of mine.

Cheers

Gordon 
Ps I cast 1/2 lb cannon shot from an aluminium mould with no vents and it works fine when the lead and mould are hot enough.

[Harnic]

Well again it wasn't the brushes fault it was the painter. I tried again this evening and got perfect casts almost every pour. I think I only had 2 culls out 75 balls. Part of my problem was I was pouring too hot. I tried a lower temp. Canted the mold a little and poured very slowly and held the ladle at the mold for a while as the mold cooled and allowed it to syphon more lead in as it cooled. I gave the mold about 3 seconds to cool before opening and that did it. I didn't realize how much thes big diameter balls shrink as they cool.
Thanks for all the input. Problem solved!

There ya go David!  It happens to all of us, more frequently that most would admit! You just held your mouth wrong the first time!

[docone]

I am wondering on how pure the alloy is. It sounds like #2 alloy.
At any rate,
Make sure the mold is hot! As the metal cools, it shrinks. People will tell you to add tin, or make vent lines, nah.
Heat will do it.
Keep a metal column over the casting. That keeps the shrinkage under control. As the mold metal cools, it pulls down the sprue column.
If you got a bubble, you need to heat your mold. If it is crystalline at the cut off, that is almost normal. Put the sprue on top as you load it and ramming will fix the crystalline at the cut off.
Heat is your friend.

[dagner]

 the bevels did several articles over the years in muzzle blast  on how to cast balls with no viods  read them you used to be able to down load them  from nmrla web site
dag

[Southron]

A little, little bit of pure TIN in your lead pot will make your round balls come out almost perfect. In addition, they will be shiny like silver.

I generally just go down to the local hardware store and get a spool of 50/50 Lead & Tin Solder Wire. Don't get the Acid Core wire-just the regular wire solder. You can precisely control the amount of Tin in your pot by measuring the length of the 50/50 solder wire you put into the pot. Experiment with different lengths to find the optimum amount.

GOOD LUCK!!!

[dagner]

 southtron   go to recycle yards they are all over   check for the 5 lb plumber blocks  they come in blocks of 6 but you usualy just see a single one cut off    pure lead we get them for around  1.00 a lb  pure virgin soft lead  and would be suprised how many are at recycler
dag