Industrial Shaft

It is an arbor for a buffing wheel. You could either put a coupler on it and extend a arbor for a grinder or buffer which is why there is a key slot. Or likely a machinist mounted it in his lathe chuck for buffing operations. It was machinist made and is not a production item. HSS stands for High Speed Steel. SLH-8 Likely stands for Standard Left Hand 8 threads per inch. HRR baffles me, my just be his initials. This is very large buffers that have shafts this thick cost thousands of dollars. I could also have been made to be mounted on pillow blocks and run a belt sheave with with the keyway. The link should give you a better idea.

References:

https://www.google.com/search?q=industrial+buffer+arbor&rlz=1C1JPGB_enUS691US...

Reason:
Could you provide a reference link to the actual item?

In short, NO. No website for this actual item will exist. The fact that the material (HSS) and thread pitch (SLH8) is hand written on it clarifies that it was custom made. As a machinist one of the most difficult things to do is identify unknown steel alloys. Even with many shop tests the actual steel alloy can only be identified with an educated guess. The only way to truly know what kind of steel it would be, is by foundry records or scientific analysis. Since this is marked then it was manufactured by the person that hand wrote on it. HSS or M2 is a special steel and quite expensive and difficult to manufacture. No company would use it, they would use High Carbon Steel and case harden it. Thinking more about this there is not enough space for a buffing wheel. So I would change my opinion and say it goes to an industrial circular saw. On this link, about 1/4 of the way down you will see "arbor components" that is what this is. Like I said though this is custom made. you will not find a website for this item, unless the machinist has one for his shop, which is unlikely though because machinist take pride in there work and would have a permanent mark to advertise their quality.

References:

http://www.sawcenter.com/unisawparts.htm

Reason:
I understand what you mean. But the examples you provide are a lot smaller than this item. I'm going to take another picture while holding the shaft to reveal how large it is and hopefully that will help get it identified.