Horizontal router table: Bit above or below table?

[cabinetman]

Well, I agree that you are right in what you wrote. However, anyone that knows how to set those up would also know that it would take 2 - and infeed and an outfeed. I just didn't want to frighten everyone with the $1000 plus unit. I should have mentioned this in the first post.

It's like getting a massage. One masseuse is good...two is better...if you can afford it.

Power feeders may seem like a luxury, and they are to an extent if their use is only occasional. But for those that have ongoing use, they are not only an efficiency measure, but a safety one, especially on a shaper. Multiple mounting bases can be purchased for quick set up on different tools.
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[JimD]

Another factor I did not see mentioned about the above the board arrangement is limiting the depth of cut. I have a horizontal router table and the bit is below the work. I have also used a normal vertical router table to make crown moulding. If I wanted to use the bit above the table, and the original question makes a valid point about supporting the back, I would have the bit exiting a board with zero clearance or at least have a second horizontal table surrounding the bit so that the board cannot jump up into the bit and thereby substantially increase the depth of cut.

I agree with the points about not trapping the board between two opposed horizontal surfaces, however. To avoid that, you could make the upper surface, including the router mounting, on a spring or something so that it would give if the forces got too high. That would help with the primary risk of kickback. If both horizontal surfaces are rigid, the kickback potential will be the highest with the most force. A stock feeder may be able to resist the kickback but it also might not. I agree it would increase safety because you could adjust the feed rate and keep it consistently within the routers capability (ignoring the potential for things to change if you come close to a knot or something).

The overall conclusion, no easy way to do this safely, seems correct to me. It is also true that no matter what your arrangement, you will depend on the moulded surface to support the piece in some manner. If the bit is above, the moulded surface much contact the upper table to limit depth of cut (at least that is what I would do). If you use the bit vertical, then your moulded surface is against the fence. That worked fine when I did it.

Jim

[bdk5]

Isn't the solution to the original problem (i.e., the stock on the outfeed side having insufficient support if the bit is cutting from the bottom) to start with wider stock than necessary, cut the profile on the router table, then rip the molding to the appropriate width?
Also, as for featherboards above the table, they are designed to compensate for the possibility of kickback. Because of the angle at which the "fingers" are cut, the featherboard prevents the workpiece from being thrown back at you. With the bit over the table, the nice smooth table underneath does nothing to prevent the stock from being thrown in reverse.