Plasmech,
As mentioned, he's trying to demonstrate a style of a relief cut on the compression side of a branch that is theoretically under tension, that is to say, imagine that when that tree fell, the skinny end of the branch got pushed up hard against the trunk of another tree out of camera view. (Unfortunately, his chosen example is a poor one, it's not tensioned that badly, but imagine that it is.)
If you were to cut the branch in one go from the tension side, all that pressure is released in an uncontrolled fashion and the butt end of the branch will jump violently as the spring is released, possibly hitting you where you would prefer not to be hit. So you want to release some of that springs potential. Dig it so far? Knew you would.
Now, if you cut straight in from the compression side, your saw might get pinched as the kerf of the cut closes, often quickly and to your great embarrassment. So what our farmer is trying to show is paring away at the compression side bit by bit, but he hardly does enough to really call that a relief cut.
Another critique I have of this really quite poor demonstration video, and one that I think is important for a new saw operator such as yourself Plasmech: watch really carefully at the end of his relief cut, it's hard to see, but just as he cuts in past that little twig, he flicks the saw sideways to cut free the tiny wedge he's made. This is a recipe for derailing the chain off the bar, or "throwing the chain".
Granted, he was properly using the tip of the bar to do this, and granted, it's a valid technique in the portfolio of chainsaw carving artists.
But for new operators like Plasmech, let's get back to some basic high school physics: Though your chain seems to run in a channel on the bar, at speed the rotating mass of the chain is trying to describe a circle, limited to an ellipse by two points, the drive sprocket and the bar tip. Any application of sufficient sideways force between these points attempts to derail the chain.
Hope this helps.
RedlineIt
