Complex sentence: Until the early 17th century there were workmen called Slitters who cut up iron bars to a suitable size for Nailers to work on, but in 1590 the slitting mill was introduced to England, providing a mechanical means of producing rods of uniform cross-section.
Split into simpler sentences: Until the early 17th century there were workmen called Slitters who cut up iron bars to a suitable size for Nailers to work on. In 1590 the slitting mill was introduced to England, providing a mechanical means of producing rods of uniform cross-section.