I'm sure the wood jointer was the most frustrating tool for me to figure out how to set and use, but I stuck with it because I understood it was the foundation of everything I wanted to make that was straight and flat, and so I had to make sure I knew how to set up and use the jointer ... but I also learned there is a lot more to jointing wood ...
Watch it on Youtube: https://youtu.be/vb_s-NSxiyw
And one of the first things I learned was that setting up the jointer is job number one, and it needs to be done correctly or nothing else matters ...
The jointer knives need to be slightly proud of the outfeed table, in my case about the thickness of 3 or 4 sheets of paper. The technique for setting these is covered off in previous videos and articles. To see those types "jointer" in the search box and click enter, you will see a list of articles having to do with the jointer.
The second setting is that the fence is absolutely 90 degrees to the outfeed table. If the fence is also 90 degrees to the infeed table, that is perfect, if the fence is not quite perfect to the infeed table, but almost ... that should be sufficient. If it is off by a lot, then the infeed table needs to be aligned. Also, rarely, I have heard of twists in fences, so check that before proceeding. Oh, and don't forget to use a square that is perfectly 90 degrees. The very worst problem I had in setting my first jointer was getting the fence to 90 degrees, then I discovered the inexpensive combination square I was using was not square. I purchased a fixed, engineers square that is always perfectly 90 degrees, and my problems went away.
The best technique for pushing wood through the jointer is starting off on the infeed table, but as soon as you can safely "grab" the wood on the outfeed table, put your pressure on the outfeed table and continue to push the wood through. If your wood has an arc or bow in it, the cupping must be down, and depending on the thickness of the board, i.e. can you bend the wood by hand pushing through the jointer? then you may need to ease up on the pressure otherwise you are only transferring the cupping to a newly jointed side. You need to joint just the beginning and end of a cupped board until it becomes flat. Once it's flat, you can joint one edge of the board and now you have one flat side and one flat edge.
The first and most annoying was when I discovered my jointer blade had rust on it, at first I wondered how that happened, but then I found that all the wood I had recently jointed was now all warped, uneven, not straight, and most of all ... not useable. What happened there?? Well when the wood is not dry, what happens you skim off the top of the wood that is dry, exposing the inside of the wet wood, that immediately starts to expel the moisture. As we all know when a board expels water on one side only, very often the board can warp or cup, but this can take time depending on how wet the wood is and how thick it is. The industry standard for moisture content of wood is 9% and depending on where you live, could be up or down from that. It is always best to joint wood on one day, and then the next day, at the earliest, plane or trim the wood. It will often take a minimum of 24 hours for the wood to "relax" after being jointed, planed, or cut with a table or bandsaw. All of which can expose moisture deep in the wood and result in wood that bends or warps.
Be aware too, the built-in tensions in the wood can also cause these same bends and warps, but often it is moisture caused.
There are lots of different moisture meters, but the Wagner Meters now my favorite for accuracy, and speed of readings and no worries about poking holes in the wood, especially when I am shopping for wood at the lumber store
You can read more about them at the Amazon Store
When selecting wood for jointing, the rule of thumb is to only joint the length of wood you need. Don't start off jointing 8-foot boards unless you have the equipment to deal with longboards, and you are confident the wood is dry and stable, otherwise, you could end up wasting good wood that could have been otherwise well used.
Aside from moisture, built-in tensions that are completely invisible, can cause wood to warp or bend, but so can visible features like knots, changes in grain-like some figured woods, burls, and other features. All these can cause uneven jointing and planing.
Cupping, even modest cupping may need to be dealt with by cutting a board in half, jointing and or planing, then gluing back together. In the image below a modest cupped board, you can see from the lines how much wood needs to be removed before the board is flat. If the board is already near the thickness needed, this could easily be too much wood and end up making the board "under thickness".
Below is a severely warped piece of Holly. Jointing wood like this needs to be done in short sections otherwise most of the board would be lost to waste.
Once you start to get the "hang of it" jointing and planing of wood because easy but expect to make some mistakes along the way, I did, but it was a great teacher for me and hopefully, I can save you some of my failures ...
Copyright Colin Knecht
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