There are many ways to get wood flat, straight and square - but for this instructable I'm going to stick to using the power jointer, power planer and table saw. I'm fortunate to have access to all these tools at Techshop, San Francisco, so I take full advantage of them. I'll start with an overview of the general process of jointing and planing, then I'll show how to use the jointer and planer to fix specific defects that commonly occur in rough cut wood.
For those without the money to buy all these tools, or the shop space to house them, there are other ways. My favorite woodworking podcaster, The Wood Whisperer, has a great episode about this topic - Episode #6 - The Jointer's Jumpin. He not only talks about the method I will show here, but also demonstrates how to use some other power-tools, including handheld routers, router tables, and the table saws by themselves. You can also use hand planes to clean up wood very effectively, but I'm not yet familiar enough with that technique to write about it.
As always, I'm still a relative newcomer to woodworking - if anyone has any corrections or additional information, please share it in the comments. Just keep the criticism constructive.
Step 1: Face Jointing
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.
Step 2: Edge Jointing
- Keep the jointer set for shallow cuts - 1/32" - 1/16"
- Examine the edges and choose the flattest one for jointing
- Press the just-jointed face against the fence - it will act as a flat reference to make sure the edge is cut 90 degrees square to the face. Double check the fence with a square if you have any doubts about the angle.
- Turn on the machine, let it come up to full speed
- Feed the edge through the planer, keeping it flat against the fence and jointer table
- Continue the process until one edge is straight and flat
- Take the board with one jointed edge to the table saw and place the freshly jointed edge against the table saw fence
- Use the table saw to make a rip cut, slicing off the un-jointed edge to make it flat
Tips & safety
- Examine the edges before jointing - if one or both are severely crooked, it's best to cut them roughly before jointing. I discuss this more later.
- If you prefer, you can go directly from the jointer to the planer, and save the table saw step for last
- For thin boards, it's safe to feed them through with just your hands. For very thick boards (3" or more) you may need to use push sticks.
Step 3: Planing
Planing has several purposes.
- It cleans up the other rough face of the workpiece
- It makes the two faces parallel to each other.
- It reduces the thickness of a board very precisely
To use the planer
- Place the freshly jointed face of the board down on the planer table, with the un-jointed face upwards towards the cutters
- Set the depth of cut based on the type and quality of wood being cut. Soft woods can accept deeper cuts than very hard, dense woods. Though in general, it's best to keep all cuts below 1/16". In general, shallow cuts result in better finishes.
- If your planer has the option, adjust the feed rate. In general, faster speeds will allow faster work, but risks damaging the wood. Slower speeds will generally result in a nicer finish.
- Turn on the machine and let it come up to full speed
- Push the board through the planer. If you planer has power feed, then only push until the power feed takes over then take your hand away and let the planer do the work.
- Keep feeding the same face through the machine until it is flattened
- Once one face is flat, if you want to remove more material, start flipping the board after each pass to plane both sides. Planing both sides helps both sides absorb moisture equally, so they don't warp again after milling.
Tips & Safety
- Snipe - Sometimes when planing a board, the power rollers and cutters can grab the board incorrectly, cutting the very front and back of the board slightly deeper than the rest of the board. To avoid snipe...
- Push the board into the planer until grabbed by the power rollers
- Feed multiple boards of the same thickness back-to-back so the rollers never lose grip
- Feed the wood with the grain, snipe occurs more often when cutting against the grain
Step 4: Fix Twisted Boards
What is a twist?
Just like it sounds, imagine the board being twisted like a rope, with opposite diagonal corners being high or low. There also may be a high spot running diagonally along the middle of the board. Of all the problems, a twist can cause the most trouble, because it affects all parts of the board, including face grain, edge grain and end grain. Even a slightly twisted board can drive you crazy when trying to make precise wood joints, so it's best to fix a board's twist before fixing other defects.
How to tell
An easy way to spot a severely twisted board is to place the board on a known flat surface, for example the cast metal table of the jointer or table saw. Try rocking the piece back and forth - if the board see-saws on opposite diagonal corners, then it's twisted.
A more accurate way to detect even very small twists is to use "winding sticks." These are small pieces of wood that are milled perfectly flat, with a contrasting color mark along one edge. For my winding sticks, I used two pieces of pine marked with a sharpie. My winding sticks measure 1" thick X 2" wide X 24" long. I've included several pictures of the winding sticks, including before and after milling.
- Place the winding sticks on opposite ends of the board, and put your eye level with one of the sticks.
- Move your head until the far stick starts to stick above the closer stick.
- If both sticks look flat, and the far stick sits neatly behind the closer stick, then the board is flat. However, if one end of the far stick is raised above the closer stick, even with your eyes looking level at both, then the board is twisted.
- After several passes on the jointer, you can go back and use winding sticks to check for remaining twist. Put the winding sticks anywhere on different parts of the board to detect small twists along the length of the board
How to fix it
Slight twists can be fixed entirely on the jointer and planer. If a board is severely twisted, it's best to cut it into smaller sections before milling - each section will still be twisted, but they won't be as severe. Milling a severely twisted board whole will waste a lot of wood, because most of the board will have to be cut away to reach the straight section in the center.
If you try to fix a twist on the jointer by simply cutting the whole face of the board at once, you may end up just cutting away a layer of material without fixing the actual twist in the board. The right way is to focus on the "high" corner on each end of the board - cutting these away before planing the rest of the board.
- Before jointing the board, I like to scribble with a pencil on the face to be jointed. This helps me visualize where I'm cutting. The areas that are cut will be clean, and un-cut areas will still be marked with pencil.
- Start by applying pressure to the high corner on the front of the board as it passes over the jointer.
- If the board is twisted along its entire length, keep pressure on the high spots along the board. This will usually be a diagonal line running between the two opposite high corners.
- At the end of the cut, put pressure on the opposite high corner to finish the cut
- Repeat this process until the high spots are all cut away - then joint the whole face of the board as normal until it's flat.
After this step, the un-jointed face will still show the twist - but that's okay, as it will be cleaned up later when using the planer.
Step 5: Fix Cupped & Bowed Boards
What are cups ?
Cupping is when the faces of a board are curved along its length, with one face being convex and the other concave. Cupping happens when a board has uneven moisture absorption - the dry side of the board becomes shrinks and becomes concave while the moist side expands and becomes convex.
How to tell
Severed cups are easy to spot. Place the board on a known flat surface, such as a cast tool top. The concave side will be balanced on two edges with a gap in the middle. The convex side will be balanced in the center of the board, rocking back and forth on both sides.
How to fix it
Cupped boards are relatively easy to fix. Slight cupping can be fixed quickly on the jointer and planer - severe cupping can also be fixed, but doing so may waste a lot of wood. For severe cupping, you can cut get the most wood by ripping the board in half to make two narrow boards, both of which will be less cupped.
When jointing a cup, or any type of curve, remember to place the concave side down. There's a saying to remember this "frowns go down." This is because the concave side has two points of support resting on the table, which makes it more stable than the convex side which only has one point of support in the middle.
As with twists, I like to mark my board to clearly show my progress. And as before, do not try to press the entire board flat against the jointer. On the first few passes only the high edges will be cut, leaving a valley down the center of the board. But each pass will take away more material from the face until the entire face if jointed flat.
The convex hump side will remain on the top of the board, but this can be fixed on the planer.
Step 6: Fix Bowed Boards
What are bows?A board is bowed when the whole board is curved into a C shape on its face. Unfortunately I don't have a visibly bowed board at the moment, so I've just shown a diagram.
How to tellJust like a cup, place the board on a known flat surface and look at it. The convex side will rest on a point in the center and rock back and forth end-to-end, while the concave side will rest on the ends of the board with a visible hump in the center. On a long board a bow will also be very apparent if you hold the board at length in front of you and look down the edge - it will be visibly curved to one side.
How to fix it
Bowed boards are only a big problem if you want to use a long board whole. Using long bowed boards on projects will stress edge joints and deform a project, and trying to joint a severely bowed board flat will waste a lot of wood. In this cast it's best to cut a long bowed board into short sections, each of which will only have a slight bow.
The same rule for cups applies to bowed boards, frowns go down - place the concave side down.It's tempting to press down in the center of the board and plane the whole length of the board - don't do this. Pressing the whole board flat over the jointer will only take away material while reinforcing the bow. Just like jointing a twist or bow, you want to just plane down the high ends, and work your way down to the middle of the board.
The front end of a very bowed board will sometimes catch and stall when going through the jointer. If this happens, lift the front of the board over the cutters and complete the cut on the other end of the board. Eventually this should lower the overall bow enough to let the front end move through the cutters.
Push the board through the jointer with only minimal pressure on the middle of the board. At first just the ends will be cut, but each pass will cut away more of the face until the whole face is jointed flat.
At the end, there may still be a hump in the center of the board. This will be fixed on the planer.
Step 7: Fixing Crooked Boards
What is a crooked board ?
A crook is a lot like a bow, but along the edge of a board instead of its face. Unfortunately I don't have any visibly crooked boards at the moment, but I've tried to demonstrate with a diagram.
How to tell
To identify a crooked board, place the edge of the board on a known flat surface - one edge should be concave and the other edge convex. The concave size will be supported by two points on the ends, while the convex side will rock back and forth on-edge in the center of the board. You can also see a crooked board by holding it at length away from you and looking down one face, it will curve to one side.
How to fix it
It's theoretically possible to fix a crooked board by edge jointing, but severely crooked boards are likely to catch on the cutters and may even cause kickback. For severely crooked boards t's usually safer and cleaner to just cut away the problem areas and be left with a narrower, but straight, board.
- Using a ruler or straight-edge, find a straight line across both edges of the board. Draw a line that cuts off the convex and concave parts of the board, leaving only a narrower board in the middle
- Using a saw, cut away the outside portions of the board. I prefer the bandsaw for safe, fast rough cuts, but you can also use a variety of handheld saws or even the table saw - but be careful of kickback!
- The edge doesn't need to be clean or perfectly straight after sawing, just roughly straight. Once you have roughly straight edges, proceed to edge-joint as normal.
Step 8: Storage & Stickering
Truth be told, I don't always follow all this advice myself - sometimes I'm just itching to get working on my projects. But this is a list of best practices that I've heard from other woodworkers and pros, and a couple of these tips have helped me a lot.
Give it a restWhen you get the lumber home from the lumberyard, let it sit for a while. This lets it get accustomed to the 'climate' of your shop. This rest time could be anything from a couple days to a few weeks - the difference really depends on how different your workshop's temperature and humidity are from the source of the wood.
If you just can't wait to get started, you can also try another tactic...
Two step milling - rough & finish
Don't mill your wood to final dimensions on the first try - leave the wood a little oversized (~1/8" on all sides), this is your rough milling. Then let the fresh milled wood rest for a few days. Afterward, examine the wood again for further warping - even well stored wood can warp slightly again after milling. Now do another round of milling until the wood is the exact size you want, and use it for your project right away.
The best way to store freshly milled wood, if you're not working on it right away, is by "stickering" it inside, in a steady environment. Stickering is a method of storing wood that involves stacking boards horizontally, and placing thin spacers between each board (last picture). This is one tip that's made a big difference for me - I'm currently resawing and planing a lot of wood very thin (less than 1/2") and every time my boards were curling up like potato chips - as soon as I started stickering most of those problems went away.
Horizontal storage is better for boards, because the forces of gravity aren't working to bend boards into a bowed or crooked shapes. And stacking the boards also helps fight twisting and bowing - as the boards dry they are kept in line. Finally, the thin spacers help ensure even air circulation around all the boards. Uneven water gain or water loss is the prime cause of cupping - if one side of a board is covered while the other is open, the open side will move based on weather while the other side stays still.
No matter how you store your wood, humidity is the biggest thing to worry about. It's best to store wood inside, ideally in your actual workshop or a very similar room. If wood is stored outside or in the open air, it should be protected from the elements.
Also, if your local weather changes suddenly, your wood can also be subject to TEMPORARY warping. For example, if you live in a very dry area but experience a sudden rainstorm, there may be a lot of excess humidity that causes the wood to warp. If you leave the wood to rest a few days, it may return to its original flat and square shape.