Tool Materials and Geometry

Some General Tooling Recommendations

  • Use single edge router bits when speed is the primary consideration and finish is less important.

  • Use double edge router bits when finish is the primary consideration.  

  • Use upcut spiral router bits for grooving, slotting or when fast chip removal is required.  

  • Use spiral, straight or shear tools for natural woods depending on type of cut required.  

  • Use spiral, straight or shear carbide tools for composites, particleboard, plywood or MDF.

  • Use spiral tools when finish and/or available horsepower are problems.  

  • The cutting length of the tool is very important to the finish.  Use the shortest cutting length allowable, based on the material thickness. Using a tool with a cutting length that is longer than required can cause vibration, deflection and an inferior finish.

  • In general, the cutting length should not be more than four times the cutting diameter.  Bits with a cutting length over four times their diameter will be subject to increased breakage.  

  • Use the largest tool diameter allowable for increased rigidity, finish and tool life.

 

Solid Tungsten Carbide Router Bits

Tungsten carbide cutters are made up of very hard particles of tungsten carbide bound together with metallic cobalt. Bits produced with this material are very strong and durable and tend to stay sharper longer than HSS tools.

Carbide-Tipped Router Bits

Carbide-tipped tooling provides some of the edge longevity of carbide with the lower cost of a steel base. Carbide tipped bits are only available with straight flutes

High-Speed Steel (HSS) Router Bits

HSS is a poured material, chemically and metallurgically bonded together. The steel is processed from raw ore and heated to a liquid stage where several minerals and elements are added to improve the internal structure. Typically, HSS tool life is not as long as carbide.

Ceramic and Diamond Coated Router Bits

This tooling is worth considering when carbide’s life is not acceptable. The major consideration with these tools is the cost of the coating materials.

 

Tool Geometry and Material Types

Straight Flute

 straight flute straight flute

Use for wood and plastic operations. The straight flute design, in single or multiple cutting edges, produces a clean finish. The harder the material, the more cutting edges are recommended. The straight flute does not allow for the lifting of material out of the cut.

 

Spiral Flute

 spiral flute spiral flute

Use for aluminium, wood and plastic operations. The up-spiral flute is especially good for chip removal. When cutting aluminium and plastic, re-melting of the chips is the primary source of poor cut quality.

Use single spiral flute tools for faster feed rates in softer materials. The single-flute cutter typically has lots of room for chips, but the single cutting edge limits either the feed rate or the hardness of the material to be cut. These types of cutters are especially recommended for plastics.

Use double or triple spiral flutes for a better finish in harder materials. Double-flute bits provide a smoother cutting action because the chip load is smaller than a single-flute cutter for a given feed. This allows harder materials to be handled.

Upcut spirals are the most popular type of spiral fluted tool. Use these for grooving or slotting, for upward chip evacuation and best finish on the bottom side of the part.  These bits allow for rapid cuts since the tool clears the chips away from the material.  This type of tool is not recommended for softer materials because of the ragged finish that can result on the top surface.  This type of geometry is used whenever the best finish is needed on the bottom side of a part.

Downcut spiral tools are best used for thinner materials which will be pushed down into the machine bed rather than being lifted with an upcut spiral. They are also best for leaving a good cut finish on the top surface of cut parts. Note that the cutting speeds usually have to be reduced because the chips are pushed back into the material.  Chip extraction is generally less effective with this type of tool than it is with upcut spiral tools.

Chipbreaker

   
Use for wood roughing or hogging operations. The chipbreaker is designed to break up chips for fast, clean and efficient removal whilst reducing overall chipload.

Compression Spiral

   
Compression spirals are used extensively for cutting double sided laminates. These tools can also be used on natural woods where edge finishing is a problem with standard spiral tools. This tool will leave a clean edge cut.