TOOLING:Basic &CNC Routers

Steel, Diamond or Carbide Router Bits

Today there are so many different design features to the average router bit, profile or pattern of the cutting edge being only the most basic one. As we expand our repertoire of materials that we wish to cut and increase the speed at which we do it, industry meets the challenge by ever increasing the options in tool steel and their coatings.

Lets start with a basic discussion of what they are made of.

High Speed Steel (HSS):

This is the historical mainstay, the cheapest tool steel on the market and the easiest to sharpen. It hones to an ultra sharp edge, great for softwoods. Today most woodworkers have moved on to use oak and maple as the starting point and evolved to an entire warehouse of exotic woods. So now HSS router bits are rarely used. They just can’t keep an edge long enough to satisfy our more demanding needs.

Carbide or Tungsten Carbide:

This is the mainstay of the hobby market. I’m sure 90% of all woodworkers are using mostly carbide router bits today. Challenge is to find a good quality of carbide as not all are created equal.

Carbide can be extremely hard and brittle, and hold  a very sharp edge but the first encounter with grit in the core of MDF, or silica sand in brazilian cherry and small fragments of carbide can shatter from the cutting edge destroying a router bit entirely.

To address this issue carbide is most often “mixed” to be more malleable, and tougher to break. IN the industry they refer to this as its "toughness". They often, although not always, use cobalt as a binder and make grain size larger. Combined, this makes the router bit more “shock resistant” to withstand fracture. But this comes at a price. Larger particles make the cutting edge not as sharp or precise so the quality of cut is lost, power consumption goes up and sharpening is more frequent.

Some carbide is mixed up with specific additives that make it more chemical resistant if you are cutting a lot of melamine or P/C and the cutting edge has to contend with adhesive interactions or chemistry specific to a particular exotic wood

As in all life this becomes a trade-off. You can’t have optimum shock resistance (toughness) and an extremely sharp edge (hardness). Carbide is graded to reflect this tradeoff.. This is not a better or worse conversation, but rather an indication of its composition. Picking the right product for the application is the issue.

• C1 (K30) is a tough grade that resists impact in masonry applications and considered more of a roughing cutter with limited application in the woodworking arena,
• C2 (K20)  is the most common grade for woodworking applications
• C3 (K10) and C4 (K01) have very fine micro grains of tungsten carbide packed together with less binder to create very sharp edges that lasts longer but brittle so they don’t stand up to the newbie woodworker jamming their router into the edge of a piece of oak.. 
  
  Great for the continuous controlled motion of a CNC router where you want to maintain accuracy and not change tooling any more often than necessary. They are quite a bit more expensive and thus justified more easily in industrial applications where machine down time is more critical than absolute dollar cost of tooling.

continued HERE on why these classifications might be bogus?

More Information:

Index to everything about Router and CNC Tooling

Get the real scoop on the history of carbide and the misconception on carbide grading. Its quite a long article and somewhat directed to the metal industry but an interesting read. click HERE