We all know that Grindcore's origins come from Punk music, to the point that some people call Grindcore as "Punk on steroids".
But what are the things that separate one genre from the other? Or when do they work together?

There are so many factors that separate the two and i really have a hard time seeing Grindcore as punk on steroids. Extreme Noise Terror was and is considered Crustcore and I get that but I don't see them having anything in common with Misery. Yes there are bands that bridged the gap like Naplam Death in their early years playing a more Anarcho Punk style before losing that lineup and having the Scum era stuff happen.
Also where does Pig destroyer fit into the punk sound? I never heard it and same goes for many others.

Crustcore is such a stupid term. Not to bag on you for using it. I just don't care for it. Now back to your regularly scheduled program. I'm not sure I want to touch this grindcore topic.

I agree the term is lame i only used it since it has been used go describe them

Sure, the line is with blastbeats and the riffs. Muscially, Grindcore is closer to Death Metal than it is to punk.

Yeah, I really think grindcore is a combination of heavier punk styles like hardcore, fastcore/thrashcore, crust/d-beat with death metal.

I've talked with people about this before and while it's generally said that punk was originally a punk sub-genre more than a metal one, I feel that at this point it's a sub-genre of both and also just a fusion genre.

I belong to one or 2 grindcore groups on facebook and there are some really annoying people on there who insist on "keeping grindcore punk" and that it's not metal and was never meant to be metal and I just roll my eyes at them.

They'll bring up some REALLY obscure early noisecore related type grind bands like 7 Minutes of Nausea, Patareni, or slightly more well known ones like Fear of God, Septic Death and Sore Throat (I do very much like the latter 2 bands) to try to make some kind of a point that grindcore isn't related to metal, but lets be real, you have to go back to the late 80s or early 90s at the absolute latest to truly find a lot of non-metal influenced grind and even then most of it is influenced by metal.

I personally feel like if there's less of a metal influence then it's powerviolence or maybe fastcore/thrashcore or some type of crust punk, and in general they say that powerviolence was a reaction to grindcore becoming too metal for the punk crowd, and i can hear that because PV really does have fewer metal riffs, but at this point grindcore IMO owes every bit as much to death metal and extreme metal as it does to punk.

I also really like those heavier styles of punk, but I can hear how some of them aren't as much metal, but even a lot of those bands have been influenced by metal. It's always seemed to me like metalheads are more willing to admit punk influence in their music while punks tend to be more dismissive of any metal influence in theirs, and I really don't get why.

First blastbeat band ever (1982)

They had classic punk screaming instead of the later growling , otherwise feels like they had all elements in place for what could be considered "grindcore"?

That Asocial recording was made in 84, after "Det Bittra Slutet"

Assuck. AntiCapital is grindcore from the hardcore/punk perspective. Misery Index is grindcore from the death metal perspective. Though, if you were privileged to see the Misery Index tracks live at the time, they were from the hardcore/punk perspective.