A jointer is a workshop machine used to make one face of a board flat and one edge straight. It is essential for preparing rough lumber before thickness planing, ripping, or gluing panels. By creating a true reference surface, the jointer helps every later cut become more accurate.
Good jointer technique improves safety, fit, and final build quality in woodworking projects.
The machine works by passing wood over a rotating cutterhead set between an infeed table and an outfeed table. The infeed table is slightly lower than the outfeed table, so the cutter removes a controlled amount of material as the board moves forward. The fence supports the board at a chosen angle, usually 90 degrees for square edges.
A guard covers the exposed cutterhead and should move only as much as needed while the stock passes through.
Key Facts
- Depth of cut = outfeed table height - infeed table height, measured as a small positive removal amount.
- A jointer flattens a face or straightens an edge, while a planer makes the opposite face parallel and controls thickness.
- The outfeed table should be level with the highest point of the cutter knives or inserts.
- For edge jointing, the fence is commonly set to 90 degrees so the edge becomes square to the reference face.
- Longer jointer beds help straighten longer boards because they provide more support before and after the cutterhead.
- Safe hand position rule: keep hands above the tables and away from the cutterhead, using push blocks for short, narrow, or thin stock.
Vocabulary
- Infeed table
- The adjustable table before the cutterhead that supports the board and controls the depth of cut.
- Outfeed table
- The table after the cutterhead that supports the freshly cut surface as the board leaves the knives.
- Cutterhead
- The rotating cylinder with knives or carbide inserts that removes wood from the board.
- Fence
- The vertical guide that supports the board during edge jointing and sets the cutting angle.
- Guard
- The spring-loaded cover that shields the cutterhead except where the wood is passing through.
Common Mistakes to Avoid
- Trying to use a jointer to make a board a final thickness is wrong because a jointer creates flat reference surfaces but does not make opposite faces parallel.
- Pressing down hard near the cutterhead is wrong because it can bend a warped board flat during the cut and allow it to spring back afterward.
- Setting the outfeed table too low or too high is wrong because it can cause snipe, taper, rough cuts, or the board to catch as it exits the cutterhead.
- Removing too much material in one pass is wrong because it increases kickback risk, strains the motor, and can leave a rougher surface.
Practice Questions
- 1 A jointer is set so the infeed table is 1.5 mm lower than the outfeed table. If a board makes 4 full passes, what is the ideal total thickness removed from the jointed face?
- 2 A 1.2 m board has a bowed edge that is 6 mm high at the center relative to the ends. If each jointer pass removes about 1 mm from the high spots, about how many passes are needed to remove the bow, assuming careful technique?
- 3 Explain why a woodworker should joint one face flat before using a thickness planer on the opposite face.