I do probably equal parts blacksmithing and bladesmithing and I don't always want to use a grinder to cut steel. It has its place, but not all the time.

Would a run-of-the-mill bench shear handle annealed high carbon steels in thinner sections? Say, 3mm (1/8") or less?

I may still get one anyway, for mild steel, but I don't want to buy one and start trying high carbon in it and destroy the blades straight away.

Any advice is greatly appreciated.

Cheers,

Jono.

A Beverly B3 shear can handle up to 7 gauge (3/16”) mild steel and 10 gauge (~1/8”) stainless steel. If you anneal your metal dead soft, you might be able to get away with it. 

That said, you might have success cutting your blades hot. I wouldn’t do it on a $1500 Beverly, but here’s a video of a smith (in China, maybe?) trimming a blade with a pair of shopmade shears mounted in his anvil’s hardy hole. 

https://www.facebook.com/share/r/16KegNxXJZ/?mibextid=wwXIfr

 And here’s a cropped screenshot:

Thanks, JHCC. That is another option I'm considering. I may just end up getting both, long term. What's that principle? "Anything that claims to do multiple things will be sub-optimal at all of them."

I think I will enjoy the challenge of making my own hot shear. I occasionally daydream of making my own bench shear, but I don't know if I would 1. engineering it sufficiently or 2. execute it effectively.

I learned that principle from my old woodworking teacher (a total nutcase named Mark, who was also a highly skilled ballet dancer) as "Any machine that's designed to do two things will do them both badly." Boils down to the same thing.

How many things can a hammer do? 

I suppose you could make your own blades for hot cutting in a commercial shear.  That would be a lot easier than making a shear, and you could set the factory blades aside for cold work. 

I think my mind is a bit different when it comes to "easy" and "hard". Making a shear would definitely be a difficult challenge but it would be enjoyable in a "problem solving and sense of achievement" kind of way that would then lead to easier work in the future. Making a set of blades for a commercial shear would be a little bit like this, but the future effort of swapping the blades back and forth for hot and cold would be the kind of "hard" in terms of tedium that would bug me.

Plus, if I make a separate hot shear, I end up with 2 tools instead of 1!