0-4" yeah would cost you to much, the rings for the air gaging I think are under $200, but the column are $2,000 to I think around $5,000. Keyence is around $7,000 for the small ø to $15,000 all tricked out. Laser would be the best for grinding. My last company we had 2 laser mikes, they work great but are to big and not designed for shop floor, the keyence are smaller and are sopposed to be robust enough for the shop floor. I also think mitotoya also has lasers like the keyence systems.