a small grub screw locks the gearbox axle into place, spinning it. it readily works itself loose and must be tightened with a hex wrench, included in the gearbox kit.

How would the previous sentence be correctly capitalized?
A small grub screw locks the gearbox axle into place, spinning it. It readily works itself loose and must be tightened with a hex wrench, included in the gearbox kit.