[jeffnc]

Do you always use a metal bead for inside corners? I have been doing a few just by filling it with mud. Or will it crack?

I'm trying to figure out how you ended up with those 2 options. I would never use metal bead for inside corners, and I would never just fill with mud - it will crack. Use paper tape on inside corners.

 

[jeffnc]

Sorry, this still makes no sense. Maybe a picture. There is no corner bead on ceilings either, only paper tape in corners. No, you can't use only mud.

 

[jeffnc]

OK, I guess that makes some sense I would normally recommend using an inside corner knife regardless. Even though many pros discount them, they work very well, especially if you don't do taping for a living. Personally I don't think the corner bead above would save much time because you still have to embed the tape the same way and you still have to use the corner knife the same way. Really the drywall itself should be straight, and the above isn't much different from just a piece of paper tape. But whatever floats your boat!

 

[jeffnc]

You need the corner knife for the same reason with corner bead as with paper tape. Paper tape forms the same 90 degree angle. What the corner knife does is allow you to mud both sides at the same time. If you use the straight knife, they do the left side one day, and the right side the next day. This would be the same with corner bead, because the issue is that the knife disturbs the mud on the other side.

I'm talking about the corner bead you showed above.

I think there is other corner bead that doesn't need to have mud in the middle of it at all, so straight knives are fine because the strokes won't overlap in the middle. (Strait Flex?)