I have a new-to-me anvil with a strange hardy. The hardy is pretty close to 1" square, but at 1" deep it becomes a round hole the same size as the pritchel. 

This is a bit tough to take a picture of, but I think you can see it in the photo below. I included a picture of the exit of the two holes to show how they both come out of the bottom round. I.E. there isn't just a piece of scrap jammed into the Hardy.

In the process of trying to fit a hardy tool into the hole, it has become apparent it is somewhat tapered too. 

So. Practical question is what are your suggestions for using this hardy? My first thought is to just fit the bottom 1" of my hot cut to the hole and let the rest project out over the top of the anvil. My second thought is to forge the bottom of the hardy down to fit in the round hole, leaving just the top inch square. 

My issue with the first idea is it sounds like it could produce a lot of stress on the anvil face around the hardy. This is not how the tools were designed to be used, so I would expect problems.

Issue with the second plan is it's a fair piece of work for each and every hardy tool I make / buy. I'm not afraid of work, but my forge time is limited and the more I spend reworking tools, the less I spend making the stuff I want to make.

I guess a third idea is to cut the hardy shank off at 1". I'm not sure if that is much better than the first idea.

 

Next up is the curiosity question. What's the deal with this? Was this a normal practice? I haven't been able to find anything in the google about it. Admittedly searching for "round hardy hole" is tricky given that most of the internet doesn't know the difference between hardy and pritchel.

Anyway. I look forward to everyone's ideas.

Interesting. Can we get a picture of the entire anvil for context?

absotively. i drug out the drop light for a better picture. It is 176 pounds. Marked in CWT. I can't read any sort of name on the side. The guy I bought it from collects big anvils and got this one as crate filler. He didn't have any additional info on it other than he imported it from england.

One other thing I noted is the edges of the Hardy appear to be dented with a radius similar to the round hole. Could it have been used with a hold fast the way woodworkers use holdfasts? I'm going to go look at pictures of how anvil holdfasts work.

Yeah. Sorry. That's a bit of a red herring and distracts from the questions at hand. Anvil holdfasts work exactly the same as wooodworking workbench holdfasts do. I was confusing holdfast and hold down when I had that question. 

Back to the interesting questions. What's the best way to get hardy tools to fit and function in this funky hardy hole? And why is it funky?

Well you could rework the hardy hole to be square all the way through with parallel sides.  The changeover should be below the hardened zone and so drill to the same size and then chisel or file or grind or a combination of them to final shape.

I do like my hardy tooling to extend under the anvil so if it gets jammed through heavy use I can pop it out tapping on the bottom; but your anvil is VERY THICK in that area so a round punch would work for that.

The sq hole looks quite long enough to hold a hardy; I would probably just make hardy tooling to fit that part and ignore the rest.

In my mind, a joint where the depth = the width|length seems "wobbly". If the depth was 1-1/2 it might seem more stable. I'm thinking about an offset shape like a small bik. With a short fuller or hot cut, no big deal most of that energy is going straight down.

Does anyone have any ideas on why this might have been made this way?

Why not baby powder the inside of the hole and then pack it with modeling clay. .The powder will act as a release agent and not harm the anvil. Remove the clay to see the exact size and shape of the hole

It may have been a second pritchel hole that got chiseled out square. Common method is drill the hole to remove the bulk, then chisel the corners. That often leaves the partial rounding on the sides that you mentioned earlier.

If you want it deeper, chisel it out some more.