Using hotplate to preheat mould

[texasmac]

Using a digital thermometer & thermocouple probe placed in the bullet cavity & with the mould setting on a hotplate, I’ve determined that the ideal starting temperature for my BACO 409400M4 .40 caliber single cavity cast iron mould should be around 575 degrees F. At that temp the 1st bullet that drops out of the mould is within 0.5gr of all the rest. At 500 degrees it requires 4 or 5 bullets to bring the mould up to the correct temperature, at 450 degrees 10 to 15 bullets is required. Of course a cold mould would require more.

BTW, I’m casting the 400gr bullet at 765 degrees with 16:1 alloy & using a PID controller. I do not monitor the mould temp while casting.

Wayne

[rfd]

i used to hotplate the moulds but gave that up for just leaving the mould on the edge of the lead pot. love my BACO JIM bpcr moulds.

[texasmac]

Guys,

I’m revising the hotplate mould temperature I posted earlier. Due to a response from an experienced caster that monitors his mould temp, I just checked the calibration of my digital thermometer setup. Apparently the thermocouple probe I was using is bad. After switching to another probe and checking the calibration, the correct hotplate mould temp is around 465 degrees F. Interesting, it’s been my experience that when a thermocouple fails it typically reads less than the actual temp rather than more.

My technique was to over-heat the mould then cast until the bullets lost their frosty appearance, at which point the mould temp was measured by inserting the probe into the bullet cavity. From experience I know that as soon as the bullets lose their frosty appearance the weight is within +/- 0.5gr of their average weight.

See the photo below for my initial setup. You'll note the digital thermometer reads 465.0 degrees and the PID in the background reads the casting alloy temp of 766 degrees (1 degree over the setting of 765 degrees).

Wayne

[Tom Herman]

Wayne,

I agree with preheating moulds on a stove or hot plate to bring them up to casting temperature.
Before doing this, it took forever for the moulds to come up to temperture and produce good boolits.
I put my moulds on the electric stove handles up (moulds on end), on a medium heat, and this about dials them in so that I'm either instantly casting good boolits, or within one or two fillings at most.
Gone are the days when I had to run out about an inch of lead from my pot just to bring the moulds up to temperature!
I haven't gotten fancy with the use of a thermocouple yet, but probably will...

[texasmac]

Tom,

Once you figure out the correct starting hotplate mould temp - sounds like you have using a stove, there's no need for a thermocouple unless a PID is used to controll the alloy temp., which requires a thermocouple in the pot. Some high volume casters attach a thermocouple to their mould and monitor the mould temp while casting. I doubt I'll ever get to that level of sophistication. At worse case my bullets drop out to within +/- 0.5gr, usually a little better. I'm convince that my bullets & loading process do not have a significant affect on my silhouette scores. It's my shooting ability and reading the wind that I need to work on.

Wayne

[RCE1]

Nice looking setup. Some will scoff, but I've found that such tight controls are very helpful in casting BPCR competitive bullets. It's really kind of a fringy thing, shooting cast bullets at 1000 meters. Having 425gr bullets that drop from the mould within a couple tenths of a grain is a real confidence builder.

[Hick]

Pretty neat stuff. If I had the space I'd try it. Don't have the space-- but what I have works . I put the mold on the pancake griddle and turn it up half way, then turn on the bottom pour pot to "7". When the nozzle starts to drip everything is ready-- and I rarely have more than a few bad bullets before everything smooths out.

[Hardcast416taylor]

I have an old 2 burner hotplate that I use to preheat molds on. I got a 1/4" thick by 7" square piece of steel and placed a piece on each burner. The medium temp. setting gets to about 575 degrees according to my thermometer. I once put an ingot of WW on the plate and set the control to high to preheat it, it got hot enough to start the ingot melting.Robert

[greenjoytj]

Guys,

See the photo below for my initial setup.
Wayne

Tell us about that little hot plate the mold is preheating on. I’ve never seen such a small hot plate. Anything I’ve seen has a single coiled burner big as a sauce pan.

[RCE1]

It's a student's model laboratory hot plate.

[texasmac]

I don't know about it being a "student's" laboratory hot plate, but it certainly is a laboratory hot plate. They are available as used on eBay.


There are several more. Do a search for "Thermolyne" & be sure it goes to at least 500 degrees.

Wayne

[RCE1]

https://www.flinnsci.com/hot-plate-s...rature/ap9162/

That's just what they are called. I have two of them.

[downwind]

Just purchased one on flea bay for $29.95 shipped

Looks like the same model as texasmac
Model 2300 (i think) with dial and goes to 700 degrees

Thanks for the introduction

[texasmac]

Just purchased one on flea bay for $29.95 shipped

Looks like the same model as texasmac
Model 2300 (i think) with dial and goes to 700 degrees

Thanks for the introduction

downwind,

When you use it make sure the bottom of the mould sits nice & flat on the top of the hotplate for good transfer of heat. If you looked closely of my photo there's a wood shim between the mould handle & the brick to ensure the mould is in full contact with the hotplate.

Wayne

[bangerjim]

I use the "sizzle method". If the boolits drop in the water a make a sharp sizzle, they and the mold are at the correct temp. Works ever time for years for me. I have numerous lab grade t/c's and digital readout and do not even use them! No need. It's all up to the sight and sound AND the experience of the caster.