When buying wood, remember that it came from a once living tree, and continues to act 'alive' even after being cut up. In the face of moisture and humidity wood can swell, shrink, twist and warp in all directions. Everything from reclaimed junkyard wood to the most expensive tropical hardwood can develop the same common defects that get in the way of woodworking projects.
I'll start by talking about the general process of face jointing, edge jointing and planing wood, then I'll talk about how to identify and fix specific types of wood defects, and finally I'll talk about how to treat and store freshly milled wood.
Examine the wood
Before touching the jointer and planer, the first step is to examine the wood, looking for twists, cups, bows, crooked edges and checks. Most boards will have some type of warping or defect, and any given board can suffer from one, two, three, or all of these problems. The best defense is to choose quality boards from the lumberyard to avoid extra work or wasted wood. But even severely warped boards can often be salvaged.
Twists, cups, bows and crooked sides can be fixed on the jointer and planer. The last problem, checks, cannot be fixed. To deal with checks you can either cut away the ends of the board with cracks in them, or choose to fill them with something like wood putty, colored glue or epoxy.
Right now I'm going to give a general overview of using the jointer and planer, then later on I'll address how to identify and fix each type of defect.
- Check the fence - the jointer fence should be adjusted so that it's 90 degrees to the jointer table, has enough room to fit the wood being worked, and is locked down so it doesn't move during operation
- Set the cut depth for very shallow cuts - I usually take 1/32" - 1/16" cuts. Jointing is very fast, there's no need to hurry by taking deep cuts. Save the deep cuts on the jointer for other tasks, such as shaping bevels or tapers and cutting rabbets.
- Place the wood on the jointer so that the grain is facing the same direction as the cut (closeup diagram). There is a saying to remember this - "pet the cat". Think of petting an animal, they are happy when you pet the same direction their fut naturally grows, but get angry when you pet them backwards.
- Cutting a board against the grain doesn't make it angry, but it can cause dangerous kickback and tear out chunks of wood.
- Some types of wood (curly wood, burls) don't have one grain direction. For these types of wood, just take very shallow and careful cuts.
- Turn on the machine and let up come up to full speed
- Keep steady pressure on the front and back of the board throughout the cut, it's nice to use a push stick (pictured) that can both hold the board down and push it forward at the same time. But keep your hands away from the cutters - imagine a small bubble just over the cutters themselves and don't touch that space.
- Continue to cut just one face until it's flat, then move onto edge jointing
Tips & Safety
- Why use a jointer + planer, why not joint both faces? - Jointing both faces would make both of them flat, but not parallel. If both faces aren't exactly parallel to start with, then jointing both of them will only reinforce the existing defect. Jointing one face gives you a flat reference to use for the planer - the planer will cut the second face parallel to the first.
- Don't joint wood shorter than 12" or thinner than 3/8" without special methods for workholding
- Keep hands away from the cutters - imagine a ~3" bubble all around the cutters, and avoid that area. If using push sticks for downward pressure, lift up the push sticks as they pass over the cutters.
- If material gets stuck, don't push it - stop the machine, extract the material and try again - perhaps with a smaller cut
- If your planer has a power-feed, be careful when feeding the board into the planer. Sometimes the power rollers can snap the board down against the table very hard - don't keep your fingers under the board.