Router bit for cross-grain rebating.

DaninVan: The wood is in this case Sapele but I would be using other hardwoods such as beech, oak and mohogany.

The bit is new, use only for, perhaps, a total running time of 20 mins. However, some people say that tool bits are not as sharp as they could be out of the box.

Do you think doing that cut in more than one pass might help?

Alternatively, do you think strengthening the face where the tearout occurs with a tape of some sort stuck on? Perhaps the brute force of the cutterwould still tear out fibres.

If I can't solve this problem I will have to confine any decoration (by inserted contrasting hardwoods) to cuts along the grain. Quite a design limitation.

A totally different aproach would be to make the top and bottom pieces slightly smaller all round, effectively providing when fitted the same slot for the hardwood strips. It would be easy to get the eges of the top and bottom to the correct size without tearout, perhaps by finish planing the long edges of the top/bottom by hand and sanding the short (cross grain) ends (sanding does not cause tearout). When gluing on the top/bottom, it would have to be very accurately centred, otherwise the hardwood strip, when finish sanded to size in place, would vary in width. Hum!

Or perhaps I'll stick to plain boxes.

Stick486:

The cut I want to make is along the edge of a piece, across the grain. I think it is called a rebate. I would remove some wood from both surfaces at that edge of the board, like the one in your first image, the piece about to be fitted in. The cut will be made along the four top edges of a box and along the four bottom edges. I will insert a square-section contrasting wood about a mm wider in both directions, glued and trimmed. A high degree of accuracy is required to ensure that all mating surfaces are very snug.

I have two problems:

1. At present I find that the geometry of the rebate made on my router table is not quite accurate enough, leaving unacceptable gaps in some points at the interfaces with the contrasting wood. The cutting must be made when the box is complete so using feathers is not possible - only hand holding.

2. Each box will be made of a different hardwood. I have experimented so far with softwood (as a trial) and sapele. With sapele (not the softwood surprisingly) the edges of the top and the bottom which have been cut across the grain shows tearout. I will try the suggestions made (tape and making the cuts (especially the first) very shallow but the tearing defeats me, so far.

On problem 2 (tearing) I have researched spiral bits and am told that a down spiral bit (either in a router table or with a hand-held router) will give a clean edge (in my case no terouut on crossgrain) on the upperside of the workpiece (router table setup - my setup) or on the lower side (hand-held setup).

I have therefor ordered a down spiral bit and will report results.

Do you think that will solve the tearout problem? (Which still leaves problem 1 which will require practice - any ideas??).

Thanks.