I'm trying to wrap my head around why a jointer alone doesn't give you S4S (surfaced four sides) lumber. I get that a table saw and a planer make the process easier and more precise. From what I've read, a jointer can only create flat surfaces at 90 degrees to each other, but it can't make opposing faces parallel. I understand the general workflow involves jointing one face, then using that as a reference to joint an edge, followed by planing and sawing the other edge to be parallel. My question is, why can't I use the same method for both edges by flipping the board? Also, I've seen mentions of compounding errors when using a jointer—how does that play into all of this when moving to a table saw?
1 Answer
A jointer creates flat surfaces but won’t align edges to be parallel. For example, if you joint one side of a board that's thinner on one end, you’ll just have a flat but not uniformly wide piece afterwards. The table saw fixes this by using the straightened edge against a fence, ensuring both edges are the same width.