How do I remove this particular cassette?
 

I have this Shimano Exage hub and 6 speed cassette on it. I want to remove the cassette and soak / clean it for obvious reasons. How is this thing held on? There is no lock ring. Looks like an actual freehub on there so I doubt this is a freewheel. There is a tab on the freehub to whack it off counterclockwise but will that remove the whole freehub?

Look up: uniglide vs hyperglide

You need two chain whips. Simply unscrew the outer sprocket, and the rest will come off.

Also looks like a 6 speed cassette on a 7 speed freehub. Not that that's necessarily a problem, but if you want to go up another cog, you've got the room to do so.

What does the outer sprocket screw into? It's already sitting over the hub splines. I tried the 2 chain whip thing and broke one of my chain whips and whacked my elbow. Ouch. I believe Sheldon's article did mention something about the emergency room. Anywho, I may have to go to the LBS, Howard at Action Bikes on Pat Booker will probably remove it for free.

Aren't the hub splines threaded?

Addendum....I fixed my chain tool with a nail and went at it again. Success! Thank you for all the advice.

The splines are threaded at the outer end, as you can see by the parts that are exposed.

This job responds much better to steady torque than to hammering on chain whip handles.
My favorite way is to arrange the whips so the handles are roughly 180° apart, lay the wheel on a bench, braced against my belly, and pull the chips towards me.

Or you can clamp one whip in a vise, with the business end hanging out the side. Then set up the wheel and use the other to try to turn it.

Looks like a 6 sp on a 7 sp spline, so whoever put this thing on probably went all the way to the bottom of the threads....and just kept going, making it difficult to remove.

I stand the wheel on the ground, position the chain whips 180° apart, and use my body weight to provide torque.

I do that but only up to a limit. However, I don't suggest it to strangers because some over commit and when the sprocket pops loose end up falling on their heads.