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After my fiasco last week launching a board into my garage wall, I started thinking about my next project - routing several 1/2" deep grooves in 6 pieces with a round nose 1/2" bit in small bites (about 105 ft of dadoes so want to do it the best way for man and tool).
Dadoes are spaced equally top - center - and bottom of each piece.
Normal feed using a table router with a fence would be right to left so the piece is moving against the rotation of the bit. But does it make any difference when making a trapped cut ... as when cutting a dado? In that case it seems the piece would be moving into the rotation either way because the bit has two flutes facing in opposite directions. Does it make a dfference which portion of the piece I'm cutting (top, center, bottom)?
Any comments? Would like to hear from the more experienced who do this often.
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The critical thing is to retain control of the work as it passes the bit. In order to do this, think about the direction of the cut. In the usual setup of work going from right to left along the fence, the front part of the bit is moving toward the fence as it cuts. That holds the work to the fence, making it easier to control. If you go the opposite direction, the cut pulls the work from the fence, leading to loss of control. In either case, one edge of the bit is making a normal, and the other edge a climb cut, so that's not a helpful way to think about it. Note that in the trapped situation where you are only trimming an edge, you might have thought this safer than cutting a dado, but it's not because in one direction you lose the force that helps you by pushing toward the fence, and in the other you are stuck with only the climb edge of the cut.
So yes, when you cut a groove or dado on a router table, move the stock in the same direction as when you profile an edge.
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I would just add a few points to what Allan wrote. In a router table, looking down on the spinning bit, it is rotating counterclockwise. So, as Allan said, when the cutter strikes uncut wood it should be pushing the workpiece toward the fence. Therefore you feed the work from right to left. The normal and climb cuts on the two sides of the groove seem to cancel each other when you are cutting a groove for the first time.
I do not think that the order of cutting (front, middle, back) will make any difference, except that you should probably cut all of the "fronts" with the same table setup before you move on to the "middles", etc.
However a climb cut, with the work flying out to the left, is always a concern whenever you decide to deepen, touch up, etc. a groove that has already been cut, or if the board rocks on the table. Once the groove has been cut it is nearly impossible to predict which side of the dado might contact the spinning cutter.
Always use a featherboard to hold the work against the fence and a push shoe, which will help to hold the workpiece down.
Doug
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Doug clarified some of my post and added, so I will try to do the same.
If you widen an existing dado, it's very important which edge you cut away. Think of it just as you would trimming a board edge: cutting the edge facing the fence is OK, cutting the edge facing away from the fence is not, for reasons described above. Similarly, widening the dado by cutting the edge further from the fence and facing it is OK, cutting the edge closer to the fence is not.
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Stop using a router table for cuts better suited to a guide and a hand held router
Router tables are made for edge work and Dadoes are not edge work
Joe
Let us not seek the Republican Answer , or the Democratic answer. Let us not seek to fix the blame for the past. Let us accept our own responsibility for the future John F. Kennedy
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This.
Like I said in the other thread, bring small work to the router table, bring the router to large work.
Once Favre hangs it up though, it years of cellar dwelling for the Pack. (Geoff 12-18-07)
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Alan S said:
Doug clarified some of my post and added, so I will try to do the same.
If you widen an existing dado, it's very important which edge you cut away. Think of it just as you would trimming a board edge: cutting the edge facing the fence is OK, cutting the edge facing away from the fence is not, for reasons described above. Similarly, widening the dado by cutting the edge further from the fence and facing it is OK, cutting the edge closer to the fence is not.
I understand that, but thanks anyway for the reminder. In this case it's increasing the depth of the dado cuts - taking shallow passes to attain a depth of approximately 1/2" with a 1/2" bit. Three dados on the front side; five on the back side, 7 pieces like this. If I had a table saw I would probably try pre-forming the dados with a blade stack and then make a final pass or two with the profile router bit. Don't have, so doing it the long, hard way.
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"Stop using a router table for cuts better suited to a guide and a hand held router Router tables are made for edge work and Dadoes are not edge work" packerguy® said:
This.
Like I said in the other thread, bring small work to the router table, bring the router to large work.
Both this and that 
Worst thing they can do is cook ya and eat ya 
GW
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There was a day that this guide was required buying, for a noob woodworker. But then PC 690's and 890's ruled the router world. Now either something store bought like this or a Ho made guide similar in design are useful on a wider selection of routers. Ho madeGenerally the cheesy ones packed with the tool are hard to use, and maybe not so accurate. For just Dado work, and easy project, and an awesome adjustable jig is seen below. https://www.youtube.com/watch?v=7j4vGS4HY-8Also brings proof of Joe's comment in another thread that jigs are what thinking woodworkers do 
Worst thing they can do is cook ya and eat ya
GW
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