Heating Molds on a hot plate

[SSGOldfart]

I put an old skill saw blade on top of an electric element hotplate.



I keep ingots on the hot plate as well, to pre-warm them. Linotype ingots go slushy sooner (at a lower temp) than WW or pure lead ingots on an overly warm hotplate - ask me how I know this.

Despite over warming moulds to the point of melting ingots on the skill saw blade next to them, I have yet to warp an aluminum or steel mould using a hot plate. I also use the hot plate to heat cycle brand new moulds a few times, before casting with them.

I use a coffee can lid (mold oven) on top of the hot plate if it's cold, or very windy outside



When I add the lid, it often requires that I turn down the heat some. (or else ingots melt) The lid really helps contain the heat on a windy day.



- Bullwolf

mine is not as fancy as this one but a cheap pot from the dollar store works great in place of the coffee can

[Retumbo]

What he said. I will take a picture tonight of my set up and use my Infra red thermometer to read the temp of it.

What the check is that? Looks like a useful idea.

That is a strip heater... meant to be mounted to a flat plate, so if you mount it under a piece of aluminum plate, you have a 'hot plate'... lol

[1911KY]

I use a solid surface hot plate set on Medium, anything higher and ingots begin melting...learned this the hard way! I always make sure my blocks are closed securely before sitting them down and haven't had any warping issues so far.

My hot plate gets hot enough to melt lead on the highest setting but will not sustain that temp as it continually kicks on and off. It does a fine job melting pewter though.

[Oreo]

Can anyone here testify of actually themselves warping a mold on a hot plate? Have been watching for maybe 5yrs now. This subject comes up occasionally as some kind of folklore but I've never found a person who has actually done it.

I've come up with my own theory that the heat from a normal kitchen electric hot plate isn't enough to warp a mold by itself. If it happens at all I say there's something else going on.

[bangerjim]

Warping could (remotely possible) happen if you put a very cold mold on a very hot surface and the heat did not transfer fast enough. Al is an excellent heat conductor and should heat up fairly rapidly and evenly.

Still, there are those "tales of woe" out there that talk about warpage. I have never seen it on any of the 35 Al molds I have. My HP is usually set to around 670F and the molds are in intimate contact with the flat surface.

Just don't put a frozen mold on a 1000F hotplate or you may just find out.

Just my thoughts from an engineering background.

banger-j

[country gent]

ANother reason why warppage isnt as big an issue is most manufacturers are using low stress alloies or stress relieving the material before machining the molds. Internal stress can cause materials to walk and move when heated or being machined. Stress relieved helps to lower this problem alot as does the way blocks are machined. Slowly heating to temp and bringing mould to temp in steps helps alot also.

[Shooter6br]

Here is what i use

[dragon813gt]

Every mold is different but I don't go above the halfway setting. I'd rather have it take a few pours to bring it to casting temp then warp a mold. Ask me how I know

[Iron Mike Golf]

Air temp where you cast makes a big difference, if it varies during the year. I cast in the garage and run my hotplate at 1/2 in the summer, 3/4 (or higher) in the winter.

[h8dirt]

I bring up my furnace temp' first and get a pot full of clean melt ready to cast with the temperature stabilized. Then I start heating my mold blocks and handles. I heat the blocks on a hot plate flipping them occasionally to ensure that they heat evenly. I keep a vigilant check with a 400F temp' stick. Once they reach 400F, they are ready to go. I preheat my handles to 400F separately with a small propane torch before I attach aluminum mold blocks. I hope this helps.

[Cherokee]

I preheat my handles to 400F separately with a small propane torch before I attach aluminum mold blocks. I hope this helps.

Doesn't that make it a little hard to attach hot handles to a hot mold ? I just heat everything on the hot plate - works for me...

[montana_charlie]

If I recall correctly, aluminum molds can warp from too high heat.

I think it's more likely that a mould might warp if a cold one is placed on a high-temperature surface ... or plied with a torch.
If the hotplate is cold when the mould is positioned, and they warm up together ... I believe you are safe.

Another mould oven ...

[OuchHot!]

Now that is plain genius, Montana!
I saw another mold oven where a fellow took a thrift store electric skillet with lid and put a hole in the side.

[Cloudwraith]

Anyone know of a good low-cost k-type thermocouple that is flat and sits on the surface of a hotplate? Mine is solid (ceramic? CI?) not the the coil type. I did some searching and saw some flat disk type TC's but they were $80. I think I might like to hook a PID up to my hotplate as I too have fallen victim to leaving the lead on the plate at too high of a temp. Luckily when it cooled I just pried the mess off the flat surface.

[rbertalotto]

Warping mold?....I put a very heavy elastic band around the handles to hold the two halves tightly together. I've never warped a mold.....I also put the elastic band around the handles when I let the mold cool down so the mating surfaces don't warp.

[montana_charlie]

I did some searching and saw some flat disk type TC's but they were $80.

May not fit the definition of 'low cost', but there are some here for about sixty bucks ...
http://www.ebay.com/sch/i.html?_odkw...Text=&_sacat=0

[bangerjim]

Amazing........this simple trick of using a simple hotplate to heat a chunk of metal is now turning into rocket science. OMG!


JUST DO IT! And keep on casting.

banger-j

[longbow]

I'm really simple and really cheap. I pre-heat until the sprue plate oil (or left over oil on the mould blocks) just starts to smoke. That is slightly too hot, so once I start casting the first few boolits take a few extra seconds for the sprue puddle to harden but that settles in very quickly and off I go.

Cheap easy and it works. No, I have never warped a mould in 45 years or so of casting.

Longbow

[ascast]

Temperature - I use a bi-metal thermocouple, magnetic and just lay it on the burner. Any good hardware or building / farm supply should have them- about $10.
They are commonly used to monitor stove pipe temp in wood burning country; about 3" in diameter and just stick on your stove pipe a foot or two from stove.
Temp range is up to 1000 degrees F. They are not accurate, but plenty close enough for the job and durable and repeatable result.

[ascast]

search for this on fleabay and you will see what I mean

"Wood Stove Temperature Gauge"

that is too much money, but you get the idea