Remember that all power tools are potentially dangerous. Always wear eye and ear protection when using woodworking tools. Read and understand the manuals and instructions provided with your tools, and never use a tool in a way that endangers you or those around you.
Fine furniture and cabinetry require lumber milled four-square, meaning that the sides and edges are flat and true. Don't expect to be able to buy lumber milled correctly. One reason is that only the best lumber dealers with on-site facilities will be able to do a decent job. And even properly milled lumber will move and distort with time as weather and humidity change. You may have to do some or all of the milling to get boards satisfactory for your project. This can make good economic sense when you consider that you are paying 30¢ to 50¢ a board foot to have your lumber milled at the yard.
To do you own milling you need three tools: a tablesaw (see Dr. Wood article here), a jointer, and a thickness planer. I will discuss the process of milling a board in companion article. We will be discussing the use of power machinery, but remember that all these processes can be performed with hand tools such as the plane and cabinet scraper. If you want to fully understand and appreciate the intricacies of milling and what modern machinery can do for you I highly recommend that you become proficient at hand tool approaches to woodworking. There is no more satisfying sensation than planing a board with a bench plane: The sound of the plane cutting the wood, the curl rising up out of the throat as it is cut, the smell of fresh wood, the feel of the tool in your hand.
A jointer is a very simple tool used to obtain a flat surface and an edge that is square to it. The job that the modern jointer does was handled in earlier times by the bench plane. Jointers are sized by the length of their cutter knives. Thus, the standard 6" jointer has knives (and thus a cutting capacity) of 6". The jointer has a large flat bed or table that the wood rides on. This bed is split into the in-feed and out-feed tables. Between these tables is the cutter head, which holds the cutter knives. During use the in-feed table is adjusted to the amount of wood we want to remove, and the work is passed over the cutter head from the in-feed to the out-feed tables. A fence is also positioned spanning the in-feed and out-feed tables to provide support for perpendicular faces during the jointing process.
When looking for a new or used jointer, look for a tool with a long bed to support larger boards. While some smaller table top models are available, they are really only useful if you are making models of other small projects. If you want to make furniture or cabinets invest in a full-sized 6" or 8" jointer. Make sure the bed and the other critical components are made of cast iron. Jointers made with plastic, aluminum or sheet metal are prone to vibration and uneven cutting. The only reason to have a jointer is for a clean, precise cut that is difficult to obtain with lighter machines. Other features to look for when purchasing a jointer are independent in-feed and out-feed table adjustments, dove-tailed ways (the track that the tables move in) for table height adjustment, a long sturdy (preferably cast) fence with robust locking mechanism, and a built-in dust chute. This last item is important because jointers produce a large amount of shavings that can make working difficult if not dealt with at the source of production.
Setting jointer knives can be a real headache. Most jointers have three knives in the cutter head, and these must be removed and sharpened periodically. While honing stones are available to touch-up a dull knife, there is no substitute for a properly sharpened tool. The headache comes when it is time to reinstall the knives because they must all be straight and at the same height as the out-feed table. This process can be simplified using one of the knife setting jigs currently available. These jigs magnetically hold the knives in the proper orientation so that you can tighten the chip breaker bar and secure the knives.
A thickness planer is a wonderful tool to have in your shop. Until a few years ago only the larger commercial shops could afford the large planers then available, but with the advent of the portable planer this tool is within reach of the home hobbyist and small cabinet shop. After one face of the board is flattened with the jointer, the wood is passed through the planer to obtain a smooth flat surface on the other face. The lumber is then passed several more times through the planer to finish-surface the two faces and bring the wood to its final thickness. The thickness planer alone can not mill a board flat. Planing a twisted or cupped board will yield a thinner board with the same defect.
For woodworkers without a bandsaw to resaw lumber the planer is the only way to get lumber thinner than 3/4". Even if you have a bandsaw to resaw your lumber you will want a planer to finish the sawn faces and machine the boards to a uniform thickness ready to use in your project. Although it is wasteful, repeated planing of a board is an easy way to obtain wood in thicknesses of 5/8", 1/2" and 3/8" necessary for many projects such as drawer sides, decorative boxes, and table tops.
When shopping for a portable thickness planer I suggest you take a hard look at the knives and the bed. Most portable units have a 12" to 13" wide cutting capacity, an induction-type universal motor rated at 2 HP (beware: these motors are LOUD), and all use rubber in-feed and out-feed rollers to push the wood through the machine.
The best machines use full-sized high-speed steel knives just like those found on the jointer, but some companies have begun using smaller reversible or disposable knives. The disposable knives found on some tools are downright flimsy and I would stay away from them. The problem with reversible knives is that they are smaller than full-sized knives and need to be flipped over and/or sharpened more often. Sharpening services charge by the inch, so reversible knives cost twice as much each time you take them in. In addition, the headache of setting knives in a planer is in many ways worse than that of setting jointer knives, so the drawback of reversible knives becomes more apparent. Many manufacturers are now offering Quick set knives for both their jointers and planers that overcome some of the hassels associated with knife changing.
Milling:
If you want to produce fine pieces of furniture or cabinetry you must begin with properly prepared lumber. Using boards with defects such as warp, bow, twist or cup will leave you frustrated during the execution of the project and disappointed with the results. Don't expect to be able to walk into a lumber yard and purchase boards ready to be assembled into your project. The skilled woodworker recognizes that his/her influence in a piece must start with the selection and preparation of the lumber and end with the application of the final finish. Any step left to others will usually result in less than satisfactory work.
It also makes good economic sense to purchase rough-hewn lumber for your projects. If you have a jointer and a planer you can save 30¢ to 50¢ per board foot of lumber by milling it yourself, and you will know it was prepared properly. If you purchase your wood from a quality lumber dealer with on-site facilities to mill your boards you will still need to contend with the movement of the wood after you take it home. Kiln-dried lumber has a case-hardened surface that restricts the movement of water in and out of the board. When the board is surfaced or edged on a jointer , or even when it is ripped or cross-cut on the table saw, new surfaces will be exposed. The wood will immediately begin to take up or give off water vapor, depending on the climatic conditions in your shop. Changes in water content will result in wood movement as the wood fibers swell or shrink.
After the boards for your project have been selected it will be necessary to mill them four-square, meaning to cut them to the proper width and length, and remove any dimensional defects in the boards. To do this we will use the jointer, thickness planer and tablesaw. In addition, it is useful to have a bandsaw for cutting badly twisted boards, and you will need a good trysquare to set up your machinery and check the finished pieces for square. Rough lumber is sized by the quarter inch, so a full 1" thick board is termed 4/4 (four-quarter), a 1-1/2" board is 6/4 ( six-quarter) and a 2" board is 8/4 (eight-quarter). After milling you can expect a 4/4 board to finish out between 13/16 and 3/4 inches thick, depending on the amount of material lost during removal of defects.
The first step in milling is to inspect the boards for defects and mark them on the board in pencil. These defects (warp, twist, etc.) may affect your choice of placement for the individual project pieces. For instance, an 8' long board with an inch of bow along it's length would be better cut into several shorter pieces rather than trying to mill it straight for a longer piece you may need. After you have set out where each piece will come from in your boards it is time to rough cut the boards to length. By rough length I mean one or two inches longer than the finished piece will need to be. This extra length gives you some flexibility during milling and will frequently mean the difference between a usable board and starting over if you make any mistakes in the milling process.
Begin by inspecting the end of the board for splits or checks, and cross cut the board behind these cracks. If you still see checking keep cutting until no more are evident. One good way to be sure no invisible checking is present is to cut off a small piece and bang it on the table. If it breaks a small crack was present and it will be necessary to keep cutting until the cut-off stays together. Then use a tape measure or folding rule to mark out the rough length of your pieces and use the trysquare to mark your line across the board. When making this cut it is wise to remember the old woodworker's adage "measure twice and cut once".
If the board is considerably wider than the pieces you need you may choose to rip the board to approximate width, either before or after cross-cutting to length. Be aware that ripping a bowed or twisted board on the table saw can be dangerous and result in kick-back. If the rough board displays severe defects I would recommend ripping it with the bandsaw or jointing an edge before ripping to give you a good edge against the rip fence. If you choose to rip a cupped board on the table saw put the convex side down. During any table saw cut be sure to have push sticks readily available and use them to push the wood past the blade.
After the component boards have been cut to rough size it is time to flatten one face with the jointer. Make sure your jointer knives are sharp and the fence is square to the table. Set the fence to expose a width of cutterhead slightly greater than your board width, and set the infeed table to remove no more than 1/16" of wood. If the board has any cup, I would joint the convex face because it is more stable on the table. Choose the direction of feed based on the grain in the wood, and pass the wood over the knives so they will be cutting with the grain. If your board is wider than you jointer's capacity it will be necessary to rip it in half and mill the two pieces individually. Afterward you can glue them back together and power plane the board to final thickness.
When pushing a board across the jointer always use push blocks and a push stick to keep your hands far away from the cutters. Feed the board across the cutter head keeping the edge of the board against the fence and the face held down against the infeed table. As the board moves across the cutter switch your pressure to the outfeed table. Be sure to use a push stick on the end of the board to keep your fingers away from the knives as the end passes over them. Repeat this process until a flat 'footprint' has been obtained, that is until all of the board is supported on the table. This doesn't mean that you have to joint the face completely flat, that will be accomplished with the planer.
The next operation is to flatten an edge square to the face. Do this by passing the edge over the jointer with the surfaced face held flat against the fence. If the board has a severe bend in it pass each end over the cutters until you 'lose the cut' (the knives are not touching the wood) and repeat until a long continuous cut is obtained. Use a push stick if the board is small or there is any danger of your fingers coming near the cutter knives. Check that the edge is square to the face using the trysquare.
It is now time to surface plane the other face and complete surfacing the first jointed face. If your board had severe cupping or twisting you may choose to do this step before jointing the edge. It is important to remember that neither the jointer nor the planer alone can give you two parallel faces free from defects. The jointer will remove the defects from one face but can't surface the other face parallel, while the planer can give parallel faces but can't remove cup or twist.
To plane the second face pass the board through the planer with the jointed face down. Take light passes (1/16" to 1/32") and choose your feed direction to plane with the grain. If your board is highly figured or you are having trouble with tear-out, feed the board at a slight angle to the cutters. Plane both faces alternately until the faces are fully planed and the desired thickness has been obtained.
It is now time to rip the board to final width. You may want to re-joint the first edge to make sure it is square to your faces, and then put this edge against the table saw rip fence to rip the other side to width and parallel to the other edge. Be sure that your blade is square to the table or you won't get a straight cut. If you desire you can rip the board 1/32" wider than your finished piece and joint the cut edge to size.
Finally, cross-cut one end square to the edge and cut the other end to length. If you have a motorized miterbox or chopsaw this operation can be done quickly and accurately. If you are using a tablesaw install an auxiliary fence on the miter gauge to give you a longer surface against which to support your board. Make sure the miter gauge is square to the blade and make the cut. Never use the rip fence as a stop block for cross-cutting because the board can bind between the fence and blade, leading to kick-back. After cutting the first end check it for square and then mark and cut the other end to the proper length.
Congratulations! You have milled your board square and cut it to size. Repeat this process for the other component boards in your project and you are ready to begin construction.
© 2006 Stephen LeGrue
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