First time using a grinder

I have been scrapping computers for a while now never needed to grind metal but on my 18 year anniversary my lovely wife bought my a grinder and a shop vice.
At the end of March this year we celebrated our 20 year anniversary. I wanted the grinder so I can cut a propane tank to make a smelter. (Wussed out. Didn't want to blow myself up.) Fast forward to today. I cut the top off a helium tank AND IT WAS AWESOME!!!!
The end

Collin at the farm gave me a few 6 inch zip disks made by Walter, I asked if they would fit a four inch grinder and all he said was watch your fingers. I laughed and told him thats alright as grinder cuts cauterize immediately.

The six inch zips fit my four inch grinder with just a bit of room left for the guard. The Walter disks have a built in cooling system to keep em cool, I love these disks.

Inhaling helium make you sound like Donald Duck.

I like grinding so much I took out an old bed frame and chopped it all up so I can weld (When I get my welder) pieces together and make a mold for all the metal I'm going to be melting. Ok the real reason is because I like all the sparks, and now I have a cursive capital E branded on my arm. GREAT!
P.s. Metal gets hot.

Oh My God!!!!!

Never, that's 'NEVER' use a larger disc in a grinder than what the grinder was designed for.

There's huge centrifugal forces involved and accidents with grinders never go well, or heal well either.
And always use the proper guard and safety glasses/earmuffs. You can shut your eyes, but you cannot shut your ears.

I have used angle grinders for decades and following these basic rules have only had one accident where I put a slit in the outside of one right finger knuckle.

If you want to use a big disc, get a 9inch angle grinder, and a 7 inch, and a 5 inch....

Discs and stones are made to work at specific surface speeds, go too fast or too slow and you wear the disc or grinder out.
So use a 9inch disc in a 9 inch grinder untill its a 7 inch disc, then put it in the 7 inch grinder untill its a 5 inch disc.

The grinders motor offsets the gyroscopic forces in the disc too. If you use a disc that's too big, it can take off and bite you.

There's a whole bunch of rules. I posted them in some of my earliest posts when I started.
Where to have the guard and how to hold the grinder and such.