As couple of points to clear up some ambiguities and an educated 'guess' to take things a bit further forward.
1. Ford Forge is the name of a place, and not just of a forge. It's just down the hill, on the banks of the River Till, about a mile from Ford village in Northumberland.
2. Many of the Black family are buried in the cemetery of the old church just outside Ford village, on the slope down to Ford Forge. Some of the graves are monumental.
3. The muddle over occupations seems to me to be explainable as follows: John Ebenezer Black was recorded mainly as a miller, and the mill at Ford Forge is just opposite the smithy, separated from it only by the river. The mill was water powered and is open today as a working museum.
The Wait(e) family into whom John Ebenezer married were occupied with spade making, - hence the association with the smithy.
William Wait, the father of John's two wives, it seems (they were sisters or half-sisters?) is recorded as a spāde-maker in Main street, Spittal, Tweedmouth.
Spade-making was an important activity in the local economy.
It seems too that the religious connections of the two families, Black and Wait, were strongly Presbyterian.
Hope this helps those interested.
John