Router Bit-of-the-Month (May 08)

The featured router bit this month is a stunning bit from Carb-i-tool (if you are into that sort of thing!!)

It is a solid carbide, 3 flute, up-spiral bit. These are commonly made from either HSS (high-speed steel) or solid carbide because of the difficulty in producing a carbide tip that fits around the required curve.

Upspiral carbide router bit

As you can guess, it is razor sharp, and significantly heavier than your standard bit because it is solid carbide.

There are a couple of reasons why you would use a bit like this over a standard straight, 2 flute cutter. The first is most definitely finish. A straight cutter chips away like a high speed chisel at the timber, and at 22000 RPM is a lot of chisel cuts over the surface of the material, and the finish is pretty good.

However, some materials don’t like being chipped at (and all would prefer being sliced if possible). This is where this cutter comes into its own. This cutter slices at the fibres, and pares away the material leaving a superb finish. I will hopefully have some time to do a video of this a bit later on (when the shed upgrade is more complete!)

The second function is chip removal, and the up spiral (or down spiral for the other form of the cutter) pulls the material out of the cut zone and away. It is called “up” because of the direction the chips would move if this was mounted in a handheld router. This is good if the finish surface is on the opposite side to the router. If not, then you need the other direction – ie a down-spiral bit. Finally, if both surfaces are important (and prone to chipout or tearout), then you need a compression bit (that I wrote about a number of months ago)

Being solid carbide, these bits are not cheap (around $110), but given the spiral, and the three flutes (ie cutting faces) rather than the standard two, this will produce an excellent machined surface.

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