So I torched and ground this Drillhammer into to shape. 

Does anyone have experience with hardy tools made from HSS steel? I made this thinking that a hard and high thermo-plasticity would make it a superior hot cut? (Of course in combination with an anealed hammer) I have also made a plate to keep the HSS from touching the anvil face (contact surface was a bit to small for my taste)

We call those "Jack hammer bits,"  this side of the pond. That would be a "spade bit". They make fine hardies.

Frosty The Lucky.

Grant had a career resharpening those types of bits here in the USA and he said they were almost always 1050.  Cheap was a controlling factor over "better"!

Spark test will clearly indicate the difference between HSS and plan carbon steel.  What did it spark like when you ground it?

Mine was definitely 1050 and won't mark a hard hammer face---lots easier to touch up the grind on the hardy than to reface a hammer! I've been using it for over 20 years so far

It created long and darker sparks that did not fork. 
To clarify a bit more on its origins, it was used as a part in the cement industrie, not in a more conventional/portable tool.

Does sound like HSS or high alloy steel; maybe S series like S5 or S7.

Mine was used with a portable tool---(weighed about 90 pounds) and was used to tear up streets and was powered off a large engine powered screw compressor.

On 16/04/2018 at 8:13 PM, Frosty said:

We call those "Jack hammer bits,"  this side of the pond. That would be a "spade bit". They make fine hardies.

Interesting terminology, this side of the pond we know those pneumatic/hydraulic hammer (or jack hammer) bits as 'tarmac cutters', what we refer to as 'spade bits' are curved like a spit and used on clay or compacted stone agrigates. All the same metalurgically though so all good for hardy toolling.