You can't win :)
A new base with all the junk to set up a proper forge, smelter, etc requires... a fair chunk of metal bars hauled over to rebuild all the forge stuff. Or hauling the ore back home ... either way, you can't really portal it.
That leaves you options, all of which have pros and cons.

- make a new base, full or partial, with a full forge and bench setup.
pros: proper repair station, handy while working ore nearby, access point to a region, etc
cons: can be raided when you are working, splits your metal supply, extra materials to build the needed stuff, etc

- haul the ore to your main base:
pros: a lot less setup and rebuilding. Can be very fast if you can find mining spots near shore and not that far from your home.
cons: even as a one-way trip (portal over, collect ore, boat back) its annoying and possibly risky at sea.

- find a new mining site that is easier to get to:
pros: much less hassle all around
cons: maybe none exist, some maps are awful esp for iron, and exploring takes time.

- relocate entirely:
pros: if your new site has access to all biomes, its mighty handy to get what you need efficiently. If you were going to rebuild anyway (stonework, etc?) may as well do it now.
cons: its a lot of work and you 'lose' the home you probably sank a lot of time into(?)

side note: iron is critical for the whole game esp if you build a lot. Handy access to it is therefore also critical.
Personally, having played several maps ... I would explore first, see if you missed a better mining spot. It is rare for bonemass's place to not have some crypts. While looking for a better spot, consider alternate main base locations I guess?