causes of a forge cracking

[Ken G]

I'd like to know what the thoughts are on the causes of a forge cracking? Is it heating up to fast? Cooling off to fast? Not linning? Do they still crack with some sort of lining in them?

I figure someone here has had one crack on them at one time or another.

Cheers,
Ken

[Ridgewayforge]

If you quickly cool a hot piece of cast iron, it will crack. too much water poured on a hot forge will cause it to crack.

[Frosty]

What kind of forge? If it's a cast iron forge pan that has "clay before using" it's probably heat checked. Pouring water in the center of a HOT cast iron disk is going to cause huge stresses as the center shrinks more than the outside. There are a couple opinions about claying a forge. First a couple inches of clay packed into the pan will soften and spread the heat to the pan so it's less stressed. The down side is clay can trap water against the pan accelerating corrosion, not to mention sulfur in the coal making sulfuric acid when mixed with water.

Take it easy with wetting the fire no matter what you decide.

Frosty The Lucky.

[Ken G]

I always clay my forge and I recon I will continue. The forge stays inside so rust is not a hge concern. Any water I put on is around the edges from a sprinkle can. The ones I have seen that were cracked looked to be some sort of cast metal.
Just curious.

Ken

[clinton]

I use a ''WATER MOP'' as shown by Brian Brazeal and Alfred Habermann, it does not put out too much water. Too much water is what causes most fire pots to crack.

[ThomasPowers]

I had a cast iron forge crack the first fire after it stood outside all of a cold winter. Temperature stresses.

[David Einhorn]

About 22 years ago I talked to the owner of a shop in Baltimore Maryland that was selling his equipment and going out of business. He said that his two long-time employees broke so many firepots by dumping water on them while hot that he had special firepots cast for him that were employee proof. The firepots were reportedly twice as thick as a normal firepot. Sadly none of his sons and none of his employees wanted to continue the business. He had samples of shovels and other items in his display room that were made for the Federal U.S. army during the American Civil War, so his business had been there for at least several generations.

[Ten Hammers]

I once purchased 2 forges from a fella ( Canedy Otto forges, round pots). NIETHER (pot nor forge) was really very thick but in pretty good shape. I set the first one up in the shop and used it for I guess 6 months. Far side from the pot to the edge cracked one morning ( bloody cold morning ). Sounded like a shotgun. Much louder than a gas backup explosion.

If I do anything wet, I wet the coal before I put it in the forge. this may or may not have been the case in this issue, I can't recall. Regardless, I drilled some holes and bolted a piece of angle under the broken part for the time being.

Of course the forge was replaced. This would be the time I built the 7 ga table with a Roger Lorrance pot. ( and the other Otto forge is still in the shed). I still use the forge I built.

Thomas may have had the same issue. Thermal shock I am suspecting. As noted. castings (stoves etc) will crack from time to time when they are subject to heat /cold. I have recently been asked to repair a (likely 150 year old) dinner bell that is cracked.