Jointer and planer

They do different jobs, and the order matters

A jointer makes one face flat and one edge square to it. A planer makes the second face parallel to the first. Neither can do the other's job: a planer's rollers press a cupped board flat against the bed, plane the top parallel to the bottom, and let it spring back cupped when it comes out the far side — thinner, and still cupped.

So the order is fixed. Face on the jointer, edge on the jointer, then the opposite face on the planer, then rip and crosscut to width and length. Skipping the first step is the single most common reason milled stock comes out of a planer no flatter than it went in.

You buy more than you finish

Milling removes material, and rough stock has more to remove — saw marks, cup, twist and wane are all things you pay for and then turn into shavings. The board foot calculator carries a waste allowance for exactly this, and it varies by how far the mill has already taken the board.

The practical consequence is that a project needing twenty board feet of finished parts is not a twenty board foot order at the yard.

The same four shelves, bought two ways

Four shelves 30" long, 6" wide and 3/4" thick finished. Bought rough, the order is meaningfully larger than bought surfaced on four sides — and rough is usually still the cheaper way to buy, because the price per board foot is lower and you keep the thickness you mill to.

Mill it, then leave it alone for a day

Wood holds internal stress, and removing material from one face releases it. A board that comes off the planer dead flat can be visibly bowed the next morning, particularly if it was milled in one pass from rough.

The working answer is to take it close over two sessions rather than one: mill to roughly a sixteenth over, sticker it with air on all sides overnight, then take the last sixteenth the next day. Parts that go straight from the planer into a glue-up are the ones that surprise you.

What this page does not tell you

• —The waste percentages are the allowances this site's board foot calculator uses, and they are rules of thumb rather than a guarantee about your particular stack. A board with a lot of twist can eat far more.
• —Thickness is where rough stock pays: 4/4 is a full inch off the saw and dresses to about 13/16", so a finished 3/4" part is most of an inch of purchased wood however you buy it.
• —This page says nothing about which machine to buy. A lunchbox planer and a jointer plane will mill stock perfectly well; so will a hand plane and patience.