How large should the space between carpet tack and metal edge for tile be?

Tackless (carpet tack strip) is not usually put in door ways ot areas that are walked on.

The padding is cut back about 1'' from tile and the carpet is folded into this void and stapled down with an upholstery staple gun. The metal binder bar is installed over the joint.

If edge of tile is clean and carpet is tight to it, it can be left as is.

Chuck