It also depends on what you are grinding. If it is a small piece, say 1x1", doing it manually is not such a big deal compared to cranking back and forth on work that fills the 6x18" work surface. Even on small parts, the automatic machines shine, there is a hand lever where you can reverse the power feed manually, and effortlessly, just by gently switching it back and forth as the grinder clears the work, leaving the other hand to control the down feed and the cross feed. Even with the power feeds a finish pass might be done by hand.