Flattening a board with a router table?

No.

-- Michael :-{| Diapers and politicians both need to be changed often; and for the same reason.

I did this for years! Many moons ago, on another planet, (read, my first marriage), I was not allowed to buy the proper tools, even though I was making commission pieces, and professionally refinishing for years. I took a homemade router table and did exactly what you describe. If I remember, it was a Craftsman router with a straight bit, a broken light and a stripped locking nut. What fun!! Used to keep a set of locking pliers on the bench to change bits.

To be honest, the results were mixed, and overall, not too good. When a piece is say, cupped, you start off knocking off the edges. Then you come back through and maybe get another inch or two, and probably leave some lines which are actually different levels on the wood. You quickly find out that .002 on a router table part turns into a much bigger mistake on your piece.

What I finally did was to buy an electric planer from Harbor Freight and had much better results with that, after ruining a lot of wood to make it work.
Finally, I changed my life and now I have a nice planer. And that’s all I’m gonna say about that!!

-- Paul, Tennessee, http://www.tsunamiguitars.com

Your idea will not work. I’ve flattened small endgrain cutting boards on a router table by fastening runners on the edges which raises the wood about 1/16” above the table and raising the router bit an 1/8” above the table and moving the piece incrementally. You can set the fence so you take a pass and rotate the piece 90 degrees and take another pass then move your fence over the width of your router bit and do it over agian. It works on boards that fit your router rable. The other way to do bigger boeards with a router is to have a table wider than your board or panel and as long with the raised guides on the long dimension of said table and make a carriage for you router double the width of you table with the router in the center. some double stick tape to keep the board in place or wedges and you move the router in the carriage over the board crosswise and up and down the length of the board. Pretty simple and it’s been covered in a Fine Woodworking issue within the last year.

The other way is the planer sled or a large jointer but your idea truly will not work. I’m trying to figure out the logic you used to come up with that idea ????

BTW I’ve got 40 years in commercial shops and specialize in problem solving.

-- Few folks really know how to maximize the potential of their tools!

Google “router planing sled”

If the bit is level with the table it won’t touch the wood. If the bit is above the table it will cut but not flatten because you have no fixed reference.

-- -- Rick M.

Umm… why won’t it work (at least in modified form… listen to me on this a few lines down)? wormil’s suggestion is probably a better approach though. That’s what I do to flatten slabs (well, I do it at a much larger scale). I have a wide bottom cleaning bit (mortise) that I have set up on a bridge crossing my work table. I make passes and flatten the slab out. This is just a larger scale version of what Brett is suggesting. It is very effective and saves me a ton of time compared to trying to use a #7 or 8 jointer.

The only parts you have to be sure of are keeping the board in place and making sure the router is staying referenced to one flat plane.

So, to make the OP’s idea work, you could do something like setting the router bit 1/8 or 1/4” higher than the table. Set a 1/8 or 1/4” flat piece of MDF next to it such that the board surrounds about 1/2 the router bit’s diameter. Feed the board you wish to flatten into the bit in such a way that when you “flatten” part of the board it rests on the MDF. Understand?

References to semi-related slab flattening jigs.
http://lumberjocks.com/projects/22104
http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesArticle.aspx?id=34272

-- "Well, at least we can still use it as firewood... maybe." - Doss

If the errors in the board were small enough to sink into the hole in the table, then it’d work. That’s never the case. You have to flatten large zones in the wood, which means nothing will ever fall below the table line.

The Sand Flea drum sander works on a similar principle, but only because the drum is slightly proud of the table. That works when you can push a board through in one pass, which is not possible with a small bit.

The “router sled” works well, however…just need to clean it up with a smoother.

-- jay, www.allaboutastro.com

Yes, the router sled will definitely require a smoother, sander, or similar to get the marks out of the board. There will be marks. No doubt about it. LOL

-- "Well, at least we can still use it as firewood... maybe." - Doss