2 adjectives to describe thresher

Kurt, mounted on the seat of one of the combine threshers, surveyed with rapid and anxious gaze all the points around him, and it lingered over the magnificent sweep of golden wheat.

He long continued to have his crops threshed by hand, saying that if it were done by machines his darkies would have no winter work; but when eventually he instituted mechanical threshers, no one could discern an increase of leisure.

2 adjectives to describe  thresher