My shear mounts to the top of one of my anvils. I had only used it on upto 10mm rods but on Monday actually put it through some hot 12mm x 15mm hot spring steel. I didn't expect it to go through but it sliced it like cutting a carrot.

And what about the temper on the blades if you are going to use it for hot stuff?

The shear strength of steel drops dramatically with heat. Have you ever tried cutting bar over the edge of the anvil with a set hammer?

I used the same temper for the jaws as I use for hardies and they seem to work OK.