question about mold temps

[hornetguy]

I was curious... with all the techie guys, and gadget guys we have here... I wonder if anyone has done any research to see just what the actual temperature of the boolit mold is during casting?
I'm assuming it will not ever be the same temp as the melted metal, but just how close is it?
And, what would be the ideal temp to have the mold blocks to ensure a "perfect" pour, temp-wise?
I'm thinking about trying to work out a way to "park" the mold, if necessary, keeping it at the optimum temp, and then pick it back up and continue with perfect boolits....not losing any boolits to the re-warming of the mold.
This should be especially helpful in molding the little boolits... .22 to .25 caliber, I think. Bigger cavities seem to heat up faster and stay more constant than the little ones.
any ideas?

[Springfield]

Get an infra red temp gauge and do some testing. I'm sure it varies greatly between moulds.

[Dye]

Hornetguy
The cavity of the mould will be from 300 to340 degrees . If the cavity gets over 350 the sprue will smear. This is 1 and 2 cavity moulds and not cooling the sprue with a damp rag and cutting the sprue with a gloved hand .

Be carefull Dye

[44man]

I pre-heat my molds to 500 degrees and the first boolit will be perfect. But by the time the sprue hardens the temp will of course, be lower. If the mold was as hot as the lead, you would never cast many boolits, you would spend all of your time waiting for the sprue to set.

[leftiye]

44- Or cleaning soldered on lead off of the mold.

[beagle]

There was an article in one of the old Handloader cast bullet annuals that stated that 400 degrees was the optimum for bullet casting. This was obtained by drilling a hole between cavities of an RCBS mould and inserting a thermometer.

Now, I've found that it varies a bit between moulds. One will drop bullets better a little hotter and some want the temp cooler.

Each mould is a study unto itself as to what it likes./beagle

[AZ-Stew]

Dye,

I'm not doubting your numbers, I'm just curious as to how you collected your data. IR thermometer, or something else?

Regards,

Stew

[hornetguy]

Dye,

I'm not doubting your numbers, I'm just curious as to how you collected your data. IR thermometer, or something else?

Regards,

Stew

yes.. me, too.... I do lots of things with thermocouples at work, and was thinking about testing it, but if someone had already DONE it, then why re-invent the wheel?
I was thinking that the mold would have to be in the 350-400 range, perhaps a little hotter... I don't remember where lead starts to melt... somewhere around 450? Guess I could google it... I know that alloys will change all that, but I'm thinking worst case scenario, pure lead.

[hornetguy]

I pre-heat my molds to 500 degrees and the first boolit will be perfect. But by the time the sprue hardens the temp will of course, be lower. If the mold was as hot as the lead, you would never cast many boolits, you would spend all of your time waiting for the sprue to set.


This might be the best way to start up.... might get some slightly frosty at first, but it should stabilize at optimum pretty quickly.
Now to figure out how to build a "parking space".... for minimal investment, of course.

[lurch]

I've taken to putting the mold on a cheap hot plate as described elsewhere on this board and probably will never go back to doing it by just pouring lead till the mold heats up. About the only way I would, is if I warped a set of blocks. I was, at Dale53's suggestion, dipping the corner of the mold in the melt for a couple of minutes with the 2 cavity Lymans I have but that does not work with the 4 cavity ones - especially with the old style handles that have the hinge on the end. I don't know what temperature exactly I'm preheating to, but after the first couple of casts, they start dropping just fine. I don't get frost, just incomplete fill out to start with so the mold is getting hotter after those first couple of tries. There is an IR probe at the office that I use to warn me before I let the magic smoke out of power semiconductors on new designs that I may "borrow" next time I sit down for a session and see how hot the molds really are.

[Dale53]

I am now using a hot plate near my casting pot to preheat large moulds (4-8 cavity). I still stick the single or double cavity moulds in the molten alloy to pre-heat (30 seconds for an aluminum mould and two minutes with an iron mould). The large gang moulds are too big to work this way. The hot plate is really nice. I just set the pre-determined temperature (about medium on most hot plates should work) set the mould on it so the handles are protected, fill the lead pot and come back in thirty minutes or so. The metal is up to temp and the mould is ready to go. Couldn't be simpler.

My hot plate has a solid burner. If yours is a calrod unit, you may want to place a piece of sheet metal on top to normalize the temperature, then set the mould on that. I would be wary of placing a mould directly on a hot calrod unit because of temperature differential between the coils.

Dale53

[lurch]

Good advice on the sheet metal for the coil type hot plates. Next addition to the casting setup...

[trk]

A few years back I measured the cavity temperature using a type K thermocouple. From what I remember, the iron moulds (.358 and .45 diameters) were up around 440dF when casting well. That was from putting the thermocouple directly into the cavities right after dropping the bullets.

Someday I'll drill a number of my moulds and permanently install the thermocouples.

Until then, I'm satisfied in knowing that I don't NEED to know the temperature - just establish a routine that works and keep doing it.

I'm sure that the working mould temperature is one of those variables that will change with alloy mixture and temperature.

[Sundogg1911]

I've found that the optimum temp. for one mold isn't the same for another. the same with alloy temp. I have a Lyman .358 Keith style mold that refuses to give me a good projectile if the alloy is below 900F. most of my other molds seem to like the alloy at about 850F. it doesnt make sense to me, but I gave up trying to figure it out. I have almost the same mold in an RCBS two cavity (The Lyman is a 4) and It is not so picky. It doesnt seem to matter what alloy, or the amount of Tin. It's just a picky mold.