Pre-heating Mould With Hot Plate

[insanelupus]

For those of you who pre-heat the mould with a hot plate, how hot do you run the hot plate? If you are planning to use other moulds that casting session, do you keep moulds on the plate so they are ready to go?

Can you damage a mould on a hot plate? In theory a pair of blocks could warp, but I've never known anyone this happened to. Anyone have any experiences with this?

[hammerhead357]

insane, I use a hot plate but on top of the hot plate I set a square of 5/8 in thick steel plate that is about 6in x 6in. Then set the moulds on that plate.
I set the control knob about half way between med. and high. I set a boolit on the plate and if it melts I turn the controller down just a little until the boolit won't melt. Sometimes I will run it hot enough to melt the boolit but not usually.
I don't think one could damage a set of moulds this way but I could be wrong. I do keep other moulds on the pre-heater that I am going to use and if I need to stop casting for just a bit the moulds that I am using go back on the pre-heater also....Wes

[dubber123]

insane, I use a hot plate but on top of the hot plate I set a square of 5/8 in thick steel plate that is about 6in x 6in. Then set the moulds on that plate.
I set the control knob about half way between med. and high. I set a boolit on the plate and if it melts I turn the controller down just a little until the boolit won't melt. Sometimes I will run it hot enough to melt the boolit but not usually.
I don't think one could damage a set of moulds this way but I could be wrong. I do keep other moulds on the pre-heater that I am going to use and if I need to stop casting for just a bit the moulds that I am using go back on the pre-heater also....Wes

Exactly the way I use mine. I wish I knew this trick years ago. :roll:

[13Echo]

I folded a piece of sheet steel to hold the mould off the coils about a3/8" and made a little box of the same steel with some pop rivits to go over the hot plate and enclose the mould to hold in the heat. With a barbecue thermometer mounted on the box I can monitor the heat in the box. I try for about 450 to 500 deg F. While the lead is melting I degrease the mould and put it in the box. By the time the lead is ready the mould is evenly up to heat and, usually, the first bullet is a keeper. I think this works better than just putting the mould on the coils as it much more evenly heat soaks the mould.

Jerry Liles

[timkelley]

My hot plate has a solid cooking top so I just turn it up to about 3/4 put on the mold or moulds.

[Matt_G]

Hammerhead357 nailed it.
I don't have any plate steel to set on the top of the coils, so I just use a worn out plywood saw blade.

[Dale53]

I have long used a hot plate to pre-heat all of my moulds (aluminum, brass, and steel). My hot plate has a solid steel cooking service. If mine had a Calrod unit (exposed coils) I would definitely use a piece of steel sheet metal on top of the coils to rest my mould on. Differential heating with the mould on the coils would not be good for the mould.

Yes, you CAN damage a mould by heating it too hot. Aluminum melts at 1200 degrees and if you set it on top of a red hot coil it could reach that point. There is NO reason to heat it hotter than 450 degrees. I set my hot plate just slightly hotter than "medium". Your hot plate may be hotter or cooler than mine. Just start a bit low, and heat it until you have to make a couple of casts before they start running well. In other words, use the hot metal of the bullet alloy to bring the mould up to final heat. That way, there is no danger of overheating a mould. After you determine the best temperature, then you can hit it on the nose.

The hot plate was a real "break through" for me. The other is the little manicure fan I use to cool the sprue plate and mould to keep it at a perfect casting temperature for the entire session. The sprue hardens in TWO seconds under the fan and it keeps the entire mould at the proper temperature for continuous casting. Of course, the fan is terribly expensive (cost all of $7.49 at the local Target store - Walmart has a similar fan at slightly less cost). You will find them at the "fan section" NOT the manicure section. They are 4"-6" in size.

Dale53

[HeavyMetal]

I just started using a hot plate to keep my molds up to temp.

Using Lee aluminum molds I'll start the pot and set the molds on it while it's melting the alloy.

As it gets to the "squishy: stage I turn on the hot plate and set it for medium. I have two 1/4 inch plates I use for this. When I'm ready to start casting I'll dip the plate in the alloy on three corners until the lead doesn't stick to it.

Once it's pre heated the medium setting works great. If I used thicker steel I'd need more heat for sure.

I then set my molds on it in rotation, fill dump cycle, and I've found much better consistancy in my castings.

As to the other steel plate? I have several inch long rods with holes drilled specifically for my HP mold pins welded to it. Once heated as descriped the pins stay plenty hot and I have no fillout problem with the HP nose.

Wish I had thought of that sooner as well.

[denul]

Does anyone know if a 20 amp circuit will handle the hot plate and an RCBS bottom pour pot?

[jsizemore]

Divide wattage by voltage for each item you plan to plug into the circuit. For long time use it should total no more then 80% of the circuit capacity.

80% x 20amps= 16amps
800watts/ 110volts= 7.27amps
If the hot plat and the RCBS pro-melt have the same wattage rating then the total current draw would be 7.27amps x2= 14.54amps
For long term use your 20 amp circuit should be fine.