Jointer and Planer: Flat, Square, and to Thickness

The milling sequence

Rough lumber is cupped, bowed, twisted, and uneven. The goal is a board with two flat, parallel faces and two straight, parallel edges at right angles - the same goal as hand planing in the Hand Tools module. The order is the same too:

1. Face-joint one face flat on the jointer.
2. Edge-joint one edge square to that face, with the flat face against the jointer fence.
3. Plane the opposite face parallel to the first in the thickness planer, to final thickness.
4. Rip the second edge parallel on the table saw or bandsaw, then joint off the saw marks.
5. Crosscut to length.

A planer can’t flatten a board by itself: its feed rollers press a cupped board flat while it cuts, and the board springs back afterward. It only makes the second face parallel to the first. The jointer (or a hand plane) does the flattening.

Mill parts slightly oversize, let them rest a day or two to release stress, then take them to final size.

The jointer

A jointer has two tables with a cutterhead between them. The outfeed table is set level with the top of the knife arc; the infeed table sits lower by the depth of cut. As the board passes over, the cutterhead removes material until the face is flat.

Technique:

• Put the concave (cupped) face down so the board rests on its two edges, and the bowed face down so it rests on its ends; it won’t rock.
• Feed with the grain (the same rule as hand planing) to avoid tearout.
• Take light passes - 1/32 to 1/16 inch.
• Transfer pressure to the outfeed side as the board crosses the cutterhead; that side is now flat and becomes the reference.
• Check with a straightedge and winding sticks; stop when the face is fully cut and flat.

Jointer safety

OSHA’s rules for jointers ¹:

• Keep the spring-loaded guard over the cutterhead; it should expose only the part cutting the board.
• Use hold-down push blocks for stock narrower than 3 inches, and in practice for all face jointing; hands never pass directly over the cutterhead.
• Never joint pieces shorter than four times the width of the bed opening - a short piece can tip into the gap.
• Avoid deep cuts, which increase kickback.
• Turn off and unplug before checking or changing knives.

The planer

A thickness planer feeds the board under a cutterhead on rollers at a set height.

• Feed the flat (jointed) face down.
• Feed with the grain, and plane alternate faces to equalize stress if removing a lot.
• Take light passes, about 1/32 inch on wide hardwood.
• Snipe is a dip at the ends, where only one roller holds the board. Support long boards level on infeed and outfeed, lift slightly at the start and end, and plane parts long so snipe is trimmed off.
• Don’t plane boards shorter than the machine’s minimum (usually 12 inches or so), and never stand directly behind the board’s path ².
• Check for nails, staples, and grit, which chip knives. A metal detector is cheap insurance with reclaimed wood.

Hand or machine?

Jointers and planers do in minutes what takes an hour by hand, and many hand-tool woodworkers keep them for stock prep and do everything else by hand. The reverse is also common: a portable planer for thicknessing plus a jointer plane for faces. Either way, the sequence is the same: one flat face, a square edge, then parallel.

What to take from this

Joint one face flat, joint an edge square to it, plane the opposite face parallel, then rip and crosscut. The planer can’t flatten - only the jointer or a hand plane can. On the jointer, keep the guard on, use push blocks, take light cuts, and never joint pieces shorter than four times the bed opening. On the planer, feed the flat face down with the grain, support long boards against snipe, and keep metal out.