Using hotplate to preheat mould

Discussion on Bullets and Bullet Lubes, Casting, Swaging, Paper Patching, and Lube Cookies.
TexasMac
PostsCOLON 993
JoinedCOLON Sun Nov 20, 2005 6:08 pm
LocationCOLON Central Texas
CONTACTCOLON

Using hotplate to preheat mould

Post by TexasMac » Fri Dec 15, 2017 3:32 pm

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
NRA Life (President's Council) Member, TSRA Life Member, NSSF Member
Click on http://www.texas-mac.com/index.html to my home page containing information on my Browning/Winchester BPCR book & associated articles.

TexasMac
PostsCOLON 993
JoinedCOLON Sun Nov 20, 2005 6:08 pm
LocationCOLON Central Texas
CONTACTCOLON

Re: Using hotplate to preheat mould

Post by TexasMac » Fri Dec 15, 2017 9:49 pm

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

Image
NRA Life (President's Council) Member, TSRA Life Member, NSSF Member
Click on http://www.texas-mac.com/index.html to my home page containing information on my Browning/Winchester BPCR book & associated articles.

Arnie
PostsCOLON 316
JoinedCOLON Sun Nov 20, 2005 6:25 pm
LocationCOLON Lodi,Ca.

Re: Using hotplate to preheat mould

Post by Arnie » Sun Dec 17, 2017 6:09 pm

I found at 450 degrees with a laser temp gun works for me using a hot plate . I also made a metal cover from an electrical box and set it over the mould and a piece of ply wood over that to hold the heat in . My lead pot is 90 pounds ,so lots of time to let the mould warm up while the lead is getting to 750 degrees .

TexasMac
PostsCOLON 993
JoinedCOLON Sun Nov 20, 2005 6:08 pm
LocationCOLON Central Texas
CONTACTCOLON

Re: Using hotplate to preheat mould

Post by TexasMac » Mon Dec 18, 2017 12:23 am

Arnie wroteCOLON
Sun Dec 17, 2017 6:09 pm
I found at 450 degrees with a laser temp gun works for me using a hot plate . I also made a metal cover from an electrical box and set it over the mould and a piece of ply wood over that to hold the heat in . My lead pot is 90 pounds ,so lots of time to let the mould warm up while the lead is getting to 750 degrees .
Arnie,

450 degrees may be a little better number since at 465 degrees the 1st 1 or 2 bullets tend to be a little "frosty".

Wayne
NRA Life (President's Council) Member, TSRA Life Member, NSSF Member
Click on http://www.texas-mac.com/index.html to my home page containing information on my Browning/Winchester BPCR book & associated articles.

jonp
PostsCOLON 3
JoinedCOLON Sun Sep 20, 2015 6:07 am

Re: Using hotplate to preheat mould

Post by jonp » Sat Dec 23, 2017 7:27 pm

I havn't found that the temperature to preheat a mold needs to be that precise. I generally preheat the mold on a hotplate, test cast a few bullets then rest the mold on the plate when I'm adding lead to the pot or fiddling around some.

bruce moulds
PostsCOLON 85
JoinedCOLON Mon May 04, 2015 11:47 pm

Re: Using hotplate to preheat mould

Post by bruce moulds » Sat Dec 23, 2017 11:28 pm

using the hotplate is certainly a great timesaver.
without a temp measuring device for the mould, this is what i have found.
i put the mould on the hotplate on setting 3 ( of 4) when i light the gas.
when the alloy is up to temp, the mould will cast perfect looking bullets.
however it was noticed that the early bullets were up to 1 gn lighter than later ones when things had become stable.
all my moulds are base pour, and it turned out that the early bullets were a little smaller in diameter at the base end.
the nose end of the mould, which was on the plate, was initially hotter than the base end.
putting a saucepan over the mould on the plate reduced this tendancy.
however it pays to be aware of this issue.
keep safe,
bruce.

Brent
PostsCOLON 1587
JoinedCOLON Sun Nov 20, 2005 9:12 pm
LocationCOLON the most boring real estate west of Illinois

Re: Using hotplate to preheat mould

Post by Brent » Sun Dec 24, 2017 8:46 am

like jonp, I don't find a need for super precision in mould temperature. Frankly, I find the need for precision temperature control of mould or lead to be much exagerated on the net. I put the mould on the hotplate with my ladle so that the mould will get as much surface contact as possible with the plate. I crank the heat setting to about 3/4 and call it good. It can be set TOO hot, but it 3/4s on my unit is about right. I put a bit of aluminum foil around them to make a bit of a tent to hold the heat in. Good to by the time the alloy is ready.
I'm not from here, I just live here.

bruce moulds
PostsCOLON 85
JoinedCOLON Mon May 04, 2015 11:47 pm

Re: Using hotplate to preheat mould

Post by bruce moulds » Sun Dec 24, 2017 4:35 pm

the foil tent idea is a good one brent thank you.
keep safe,
bruce.

Premod70
PostsCOLON 87
JoinedCOLON Fri Dec 18, 2015 8:25 am

Re: Using hotplate to preheat mould

Post by Premod70 » Mon Dec 25, 2017 3:43 pm

Hey Wayne/TexasMac, I noticed in you picture that you have a RCBS furnace. Do you use this to ladle or bottom pour?

TexasMac
PostsCOLON 993
JoinedCOLON Sun Nov 20, 2005 6:08 pm
LocationCOLON Central Texas
CONTACTCOLON

Re: Using hotplate to preheat mould

Post by TexasMac » Mon Dec 25, 2017 8:41 pm

Premod70 wroteCOLON
Mon Dec 25, 2017 3:43 pm
Hey Wayne/TexasMac, I noticed in you picture that you have a RCBS furnace. Do you use this to ladle or bottom pour?
I use a dip/ladle for BPCR & bottom pour for handgun bullets. There’s no way to get the consistency I require for BPCR using the bottom pour. Also the bottom pour sure makes it easy to empty the pot into ingot moulds when changing alloys or working up a bunch of alloy for future use.

Wayne
NRA Life (President's Council) Member, TSRA Life Member, NSSF Member
Click on http://www.texas-mac.com/index.html to my home page containing information on my Browning/Winchester BPCR book & associated articles.

BUTTON_POST_REPLY