Judy Randall Jointers August 17th, 2018 - 09:26:42
Jointer size is most commonly determined by the full width of the knives (knives). A 6" jointer makes a maximum 6"-wide cut. An 8" jointer makes a maximum 8" cut and so on. It would be rare to use the entire width of even a 6" knife set at once, so the real advantage of wide knives is that you can move the fence to use a sharper place on the knife when the knife becomes dull. The wider your knives, the more use you will get out of them before it is time to re-sharpen. I usually start with a sharp knife set and the fence all the way to the right end of the cutter head and move the fence, in increments, a bit wider than the maximum board thicknesses, to the left until the knives are all used up.
Start up the woodworking jointer and let it reach its full speed before jointing any wood. Never allow your body to be to the right of the cutter knives. Always remain to the left. Hold your wood against the fence firmly, using a push block whenever the stock you are using is too small so that you can keep your hands safely away from the blades.
Depending on the price of a jointer, woodworkers and woodworking companies often consider buying it used. In most cases, smaller, lower capacity jointers are affordable to purchase new. Purchasing a lower capacity jointer new is also a good idea because, unlike industrial grade jointers, lower capacity jointers typically aren't designed to stand up to commercial level use for years on end without experiencing a drop in efficiency or dependability.
Sometimes, with curly or wavy grain structure, you will experience tear-out from the lumber edge even with sharp knives. Sometimes you can turn the board around and run it through again backwards with very shallow cuts until the edge is fully jointed and the tear-out is gone. At other times, you may have to settle for a sawn joint made on the table saw. Usually you can make fairly good glue joints this way, if you have to, but a jointed edge is always my first choice.
Originally jointers were used for the following purpose. Often woodworking projects require a flat surface that is wider than one board width. For example say you are building a table. Here you might need a width of 42 inches (about 100 cm) or more. This can be accomplished by clamping and gluing four or more boards side by side.