On one trip to the US of A we had the good fortune to be taken on a guided tour of 'Larry's Machine Shop' just outside Perry OK.
They had a horizontal drill there with a capacity of drilling 25 ft.
I asked him "What's your margin of error at the far end?"
" + 25 thou."
Crikey!
"But this is the small one. Over there," (pointing.) "is the large one. Fifty feet."
Crikey again!
Fifty ft is a looonng way!
It seems they came from a naval shipyard, and were used to drill gun barrels for warships.

The owner of Ditch Witch had come through Larry's not long before us, and had told him "Larry: if you get a larger drill you're going to have to take into account the curvature of the earth before you set it up."


Are you heading down the same path Robert?