Rabbets on a router table

[Dave Cullen]

I've recently upgraded my router table with a new router and dust collection, and my first test project was to rout the edge of a piece of 3/4 ply to fit into a 1/2 inch dado. The plan was to set the fence 1/2 inch from the bit and use the router to trim off the 1/4" (approx) leaving a 1/2" rabbet.

The problem I had is that when feeding the board into the cut, the plywood chipped out badly. Reversing direction, in climb, the router yanked the work piece from my hands and destroyed it. Not good.

I was using a 1/2" bit. What am I doing wrong?

[Ronald Mancini]

Never move material against the direction of the router bit. Plywood is the most difficult material to cut. First score the plywood with a deep cut line where you want the edge to be. Then place the material face down against the fence but out of the cutter head. Now push the material through the cutter head. Use a cutter head with a half inch shaft or larger for rabbiting.

[Pat Barry]

1) I agree with Ron. Prescoring the face material is a good idea. Use a straightedge and razor knife. You only need to cut through the top layer.
2) what type of bit. For plywood cutting like that a spiral bit would be better than a straight cutting bit
3) take multiple shallow passes. 1/4" is too deep. 1st cut I would do would be to maybe go only between 1/16 and 1/8.
4) no climb cutting. I only do that for cleanup, never for stock removal

[pat warner]

I'd climb cut but at a rate of~1/16/pass east/west. But, to be sure, plywood is not flat and you can't flatten it x hand.
As such, the depths of cut will change moment x moment. And indeed on the last pass your router may throw the sample on the deck.

[Grant Wilkinson]

I don't understand Ron's instructions. Maybe my terms are just different. For a "normal" cut on a router table, the wood is moved from right to left, AGAINST the rotation of the bit. A climb cut is just the opposite. It moves the piece with the rotation of the bit and that's why the bit can grab it and pull it away from you.

[Lornie McCullough]

The plan was to set the fence 1/2 inch from the bit and use the router to trim off the 1/4" (approx) leaving a 1/2" rabbet.

I was using a 1/2" bit. What am I doing wrong?

Dave, were you passing the plywood through the router table while holding it vertically?? I would not do that.....

Reconfigure your cutter and fence so the plywood is passed across the table while laying horizontally and the 1/2 inch you want to save is above the bit.

Lornie

[Dave Richards]

The plan was to set the fence 1/2 inch from the bit and use the router to trim off the 1/4" (approx) leaving a 1/2" rabbet.

Dave, it may be a description issue but I read your post to say that you were passing the work between the fence and the cutter. If so, don't do that. It's not safe.

If I understand correctly, you want a 1/2-in. thick tongue so you are making a 1/4 in. deep rabbet. The rabbet is what you cut away, not what is left.

[Mike Cutler]

Dave

Plywood is a pain sometimes, even really expensive cabinet grade can be problematic on a router table because of the alternating ply's.
From your post, it seems that you had the material between the fence and the bit, on end. That's a difficult cut to control, if that's what you were doing. It also sounds as if you were trying to remove too much material in one pass.

One question though;
What type of 1/2" straight bit was it? You need one with a set of bottom cutters. A 1/2" straight bit with no bottom cutters will leave a ragged edge, and bottom surface.

[Bill Huber]

If I was doing it I would use a 1/2" down cut spiral bit and lay the plywood flat on the table and go from right to left. Adjusting the fence and bit height as needed.

[Bill Huber]

Never move material against the direction of the router bit.

I always cut against the rotation of the bit, with the rotation is a climb cut to me.

[George Bokros]

Why not use an edge guide, a rabbeting bit and do it hand held?

[Bill Huber]

Why not use an edge guide, a rabbeting bit and do it hand held?

If it is a large board I will but on the router table I get a lot better cuts and if the board is a little warped my Jessem hold downs will flatten it out.

[Peter Quinn]

If I was doing it I would use a 1/2" down cut spiral bit and lay the plywood flat on the table and go from right to left. Adjusting the fence and bit height as needed.

This, with or without the spiral, is my strategy when making a rabbit on a router table. Never work trapped between fence and bit...thats how they set up baseball pitching machines. A stout router will take out 1/4" in a single pass with a sharp cutter, but the quality of cut may suffer a bit, a lighter initial pass may help reduce tearing the veneer. If you are as described running vertically from right to left with the work between fence and bit, as the cutter leaves the work its going to try to lift the veneer as it leaves. You might stand a chance running from left to right with good feather boards to hold the work to a stout tall fence.....but the odds are still against you. Lay it flat, good router bit, works fine. Sometimes you want to have a perfect 1/2" left despite varying plywood thickness, and that can be accomplished with an overarm router, not so much with a regular router table and straight bit. You could run a rabbiting bit above the work with a collet extension if the router is stout, seems like a lot of work.

[Myk Rian]

Never move material against the direction of the router bit..

Never move material WITH the direction of the router bit. That's a climb cut. It can be done in some circumstances, but not a normal procedure.

[glenn bradley]

Dave got a good lesson (thankfully without injury) as to why you don't capture your work piece between the bit and fence. There are exceptions like sliding dovetails and dados, of course. As described, one method I use is to raise the bit to full height and take about an 1/8" at a pass moving from left to right. I use the fence to control the steps and the eventual final depth. another method is to set the full depth with the fence and start with an 1/8" height of cut raising the bit for each pass. Moving the fence would be easier for those without lift capability.

[Clay Crocker]

Sounds to me like you were running the workpiece vertically against the fence and passing it between the fence and the bit? NEVER run the workpiece between the router bit and the fence. As you found, it will yank the workpiece out of your hand; consider yourself lucky that you weren't hurt. When you feed the workpiece between the bit and the fence your router becomes the propulsive force behind a wood hurling rail gun! :D

[Dave Cullen]

Dave, it may be a description issue but I read your post to say that you were passing the work between the fence and the cutter. If so, don't do that. It's not safe.

If I understand correctly, you want a 1/2-in. thick tongue so you are making a 1/4 in. deep rabbet. The rabbet is what you cut away, not what is left.

Right - tongue, not rabbet. And yes, I was passing the board between the fence and the bit. The allure of doing that is that the tongue thickness is the controlled dimension. If the work is flat on the table then the controlled dimension is the bit height and the tongue thickness is dependent on the workpiece thickness.

The bit is a 2 flute straight cutter. I think I'll try again with an upcut spiral bit and scoring the plywood before hand. And NOT climb cutting.

Thanks for the ideas.

[Shawn Pixley]

Do not run the board between the bit and the fence. This is very dangerous. I understand the appeal, but resist.