Dusty Man Stabs Woman in Shed with Round Blade

I watched part of this creepy movie on TV in the late 70's, maybe the early 80's, in Southern California as part of an afternoon horror movie marathon.

A dusty old man kills a woman in a shed by repeatedly stabbing her with a round blade. I think it was a tool he found in the shed. Later in the movie he pulls a women into an open grave. They don't show what he does, you just hear her scream.

Anyone know this movie?