Wavy Groove with Router Bit

[Denise Palko]

I am building some small drawers for a case using poplar sides milled a bit thicker than 3/8". I purchased the Frued 1/4" plywood bit with 1/2" shank. (A quick test fit in some scrap shows a perfect fit.)

Trouble is that when I started to groove the drawer sides, the groove is wavy. I have the Bosch RA1181 benchtop router table that I have leveled as best I can. The fence is tightened and I completely close the gap between the split fence. But the stock still seems to catch and jump about.

The groove is only a 1/4" (or just less) so I tried doing it in a single pass. Did I skip a step in the set-up? Should I lower the bit and do this in more than one pass?

It's getting pretty near to the Christmas deadline for this project and I didn't expect this glitch. Any advice... what I am doing wrong?

Thanks,
Denise

(I don't stop by too often, so I just submitted my 2008 contribution. )

[Scott Rollins]

Are you using featherboards to hold the stock against the fence and table? I will typically take the time to use two feather boards. One to hold the stock on the table (attached to fence above the bit) and one in the miter slot to hold the fence against the fence. If you still have a problem..the router plate may be moving or the router in your height adjustment system may be moving.

[Eric McMillan]

Doing it in more than one pass will certainly help.

Another suggestion is to make sure that you are feeding in the correct direction. When the bit is spinning, the leading edge of the bit should "push" the workpiece against the fence. I don't know that it's a big deal in a captured cut but it can't hurt.

Use a featherboard. A little sideways pressure will go a long way in making the cut straighter. You could even go as far as clamping a straight board on the other side of the workpiece. In a non-through cut there's no chance of a kick-back so the normal rule of not trapping the piece doesn't apply. Just make sure the board is parallel to the fence and the workpiece slides all the way through without binding.

Increase the speed of the router. A 1/4" bit has to spin quite fast to get the edge of the bit moving fast enough. This bit can probably spin at the top speed of the router without any issue.

[Michael Stanley]

Feather boards will certainly help prevent this. especialy since you are using thinner stock I would place one from above to keep the piece tight to the table per Scott Rollins post.

[Rod Sheridan]

Hi Denise, I've often observed this and feel that it's due to the fact that the bit is rotating in the work (obviously, that's how it cuts), and the fact that both cutting edges are in contact with the workpiece, can cause it to move about.

Feather boards, hold downs etc all help, however the best solution is to use a slotting cutter to cut slots for drawer bottoms.

Not only will it cut far faster, it will cut cleaner and there won't be any wobble because the cutting edge only contacts at one point, in one direction.

(If you've ever seen a shaper running drawer parts you would appreciate the difference a slotting cutter makes).

Regards, Rod

[Tom Veatch]

...
Another suggestion is to make sure that you are feeding in the correct direction. When the bit is spinning, the leading edge of the bit should "push" the workpiece against the fence. I don't know that it's a big deal in a captured cut but it can't hurt....

Even with a captured or buried bit, the work should be fed as you indicate. Think of what's happening as the cut progresses. The leading edge cuts, the trailing edge rides free in the slot that has already been cut when the work passes that part of the bit. So your advice is good whether the bit is partially exposed or completely buried.

[glenn bradley]

A 1/4" x 1/4" slot shouldn't be a problem. If your router and fence are mounted well the movement is in your material but you probably knew that. Poplar is pretty soft and your bit is sharp so I'll also vote for featherboards to help you keep the material on track while moving from right to left through the cut.

You don't mention how powerful the router is but even a 1 3/4HP should do fine. The material should move through the cut with very little resistance. If you are having to muscle it through, something is going on. Is your table waxed?