I was wondering if anyone had a reference for the different grades of HSS. I have some T-1 HSS planer knives and was wondering if this was a decent grade of High Speed Steel.

"Decent grade"? Might be a decent grade for planer knives.
From Wikipedia:

Types

High speed steels belong to the Fe-C-X multi-component alloy system where X represents chromium, tungsten, molybdenum, vanadium, or cobalt. Generally, the X component is present in excess of 7%, along with more than 0.60% carbon. (However, their alloying element percentages do not alone bestow the hardness-retaining properties; they also require appropriate high-temperature heat treatment in order to become true HSS; see History below.)
The grade type T-1 with 18% tungsten has not changed its composition since 1910 and was the main type used up to 1940, when substitution by molybdenum took place. Nowadays, only 5-10% of the HSS in Europe and only 2% in the United States is of this type.[citation needed]
The addition of about 10% of tungsten and molybdenum in total maximises efficiently the hardness and toughness of high speed steels and maintains these properties at the high temperatures generated when cutting metals.

[edit]M35
M35 is similar to M2, but with 5% cobalt added. The addition of cobalt increases heat resistance.
[edit]M42
M42 is a high speed steel alloy made up of roughly 8% cobalt. It is widely used in metal manufacturing because of its ability to resist wear over conventional high speed steels, allowing for shorter cycle times in production environments due to higher cutting speeds or from the increase in time between tool changes. M42 is also less prone to chipping when used for interrupted cuts and cost less when compared to the same tool made of carbide. Tools made from high speed steel and cobalt can often be identified by the letters HSS-Co.

Edited July 1, 200916 yr by nakedanvil

T-1 is a decent grade for making lathe bits, drill bits, or end mills. Might make decent chisels or punches IF you can heat treat it properly. (Needs to be around 2350, plus or minus a bit, for a few minutes minimum.)

Yes, T-1 is a decent grade for making lathe bits, I agree with "nakedanvil" opinion, hehe~