multiple large cavities

[peerlesscowboy]

I encounter a casting problem occasionally, wondering if others do as well and if so, how you deal with it?
We have a double cavity mould for rather large caliber bullets, let's say .44 or .45, the mould blox are small enuf' so there really isn't a whole lot of metal between the cavities (Lyman moulds are worse than RCBS because the blox are smaller but I've had it happen with both). When you get the mould up to heat so you're getting good fillout you start getting heavy frosting and shrinkage on the side of the bullets next to the other cavity. Seems to help when that starts happening to just start filling one cavity and leave the other empty but I'm thinking..........why don't they just make the darn thing in single cavity in the first place :evil:
Is there another way to deal with this while continuing to fill both cavities? Like I'm thinking maybe......run the alloy hotter and then allow the mould more time to cool between fills?

John C. Saubak

[Artful]

frosting is caused by overheating - if you either slow down or do multiple mold blocks so they don't overheat that should solve your problem. (oh and it's best to run similar bullet sizes not .22 or .24 with .44 or .45)

[NHlever]

I cast using at least two molds. I pour about 20 boolits, and switch, or just switch at every pour. Works great to keep the mold temperatures in line. I was casting the Lyman 452460 200 gr. semi wadcutter the other day, and made some Lee 30 caliber 170 gr flatnosed cast bullets at the same time.

[peerlesscowboy]

Yes, I'm aware that frost is a sign of something is beginning to get too hot. The problem I'm having here is one side of the bullet is getting way too hot but if I try to slow the pace to let the mould cool the other side of the bullet starts showing "too cold" signs. Seems like the thin iron between the two cavities is running hotter than the rest of the mould? I've never encountered this problem with double cavity .30 or .38 caliber moulds (more iron between the cavities?)

John C. Saubak

[btroj]

I have had the problem in some moulds for big bullets but not in others. I have a 6 cav Lee 460420 mould that gives good fill out even when frosting to the max. I have had the opposite happen with my Lee 2 cav 45 Ranch Dog moulds. They both give poor fill out on the side that gets too hot.
It comes down to the individual mould I suspect. I use the same technique for both yet get very different results.

If you have trouble try using just one cavity of the mould. You have to think of it as being Siamese twin one cavity moulds!

Brad

[frankenfab]

I also go to casting with multiple molds when I encounter this problem. Another thing I do is place a box fan blowing across my knees and open the mold and hold it in front of the fan for a few seconds.

One of the best explanations of temperature control I have ever heard is that we are trying to maintain a "temperature window". I think it's a very accurate statement, and it applies to casting, smelting, and lubrisizers. Different equipment requires a different temperature window. The better you get at maintaining it, the more better boolits you make!:cbpour:

[beagle]

Yes, that happens and when you reach normal casting temp, you start to get incomplete fillout. The obvious solution is to surpass this point to where frosting and damage to bullets occur when dropping them from the mould.

Walt Melander at NIE had this figured out and had a computer model that allowed him to compute a GO/NO GO bullet combination with his common size blocks. Alas, he's gone and I have no idea. I know he made me a DC .375 mould in meehanite blocks with a 300 and a 320 grain cavity after much arguing. He said they won't throw good, filled out bullets like that. I said go ahead as I'd use them one cavity at a time. When I got the mould, he was right and ever since, I've been using it one cavity at a time.

It's all about block size versus cavity capacity and sufficient heat dissipation./beagle

[prs]

I only get that off kelter frosting with my iron blocks such as 454190. Have not noticed it with aluminum blocks and figured that was because they conduct heat better than iron.

prs

[cajun shooter]

I use brass moulds from Accurate moulds and both are 3 cavity. I have a single burner hotplate that I preheat the moulds on before pouring. I switch moulds every pour and keep them on the hot plate at about 5. I have no problems with this method of casting and if you do have a few frosted bullets they present no problems when fired. The use of two moulds will save your equipment and speed up your production.

[rintinglen]

I have a 4 cavity 457-192 and a 457-191 2 cavity. I have on occasion had some trouble as you describe, but by varying my melt temperature (as the mold gets hotter I turn down the lee pot) I have been able to cruise right on through. The 4 cavity is very tricky-1400 odd grains of lead plus sprue heats the mold up darned quickly, so the pot setting starts going lower from the third or 4th cast. The 300 grain 2 cavity seldom gives trouble, and I have never had any problems at all with my RCBS 45-325U. Casts easy and shoots great.

[Dale53]

You must exercise temperature control. My method of handling is with the use of a small manicurist's fan. They only cost about $7.00 (from Target or Walmart in the fan department). They are quiet, blow gently, and help greatly to maintain temperature. I fill the mould then slide it under the fan and the sprue sets in 2-3 seconds before I open the sprue plate. At the same time, the mould blocks themselves are cooling just enough to keep them from overheating. Here is my set up:

http://i269.photobucket.com/albums/jj80/Dale53/Castingfan-3723.jpg

Dale53

[686]

i bought a 45-70 mold in alum. 3 cav. cut in a 4 cav block. it was a 325br bullet. i had the same problume. very few times could i get good fill out on all 3 bullets with out over heating in the middle. i started casting onlt with the 2 out side cav. leaving the center cav. empty. this works good. i cast with other 4-6 cav molds 44 & 45 cal and they work good. just one of those things.

[beagle]

Yeah, a fan does help and we even experimented with bolting aluminum "cooling fins" to the handle attaching screws. That worked but made the mould handles so cumbersome that it was hard to cast with./beagle

[XWrench3]

have you tried touching the blocks to a good wet rag? or spraying it with water with a spray bottle. either of those would let you control where most of the water goes, so you could concentrate most of the heat removal to one section of the mold. the entire mold will drop some temp, but the spot that touches the water will drop the most. just make certain it quits sizzleing before you add more lead!

[btroj]

I have noticed that this seems to be a bigger problem with iron blocks that with aluminum ones. Seems the iron holds the hear better making this problem rear it's ugly head easier?
Anyone else notice and difference based upon block material?

Brad

[Dale53]

I have mould blocks of aluminum, brass, and iron with four to six cavities. It is not generally a problem with any. However, there ARE differences in how some moulds react to a particular amount of heat. You just need to learn the characteristics of each mould. Some keep good records and record the differences. I have depended on memory and experience to guide me.

I notice that when I am casting a lot (once or twice a week, regularly) I am a better caster. Fewer aggravations rear their head. However, now that I am old and have a memory that is less than perfect, I sometimes wish I had kept records.

However, I am still a BIG fan of the little manicurists fan to maintain temperature of the mould. It works better than anything I have tried in the past (including various methods of water cooling).

Dale53

[btroj]

I may have to get one of those fans. The price is right and if it allows me better control over mould temp it should be a good thing.

[peerlesscowboy]

up

John C. Saubak