Router Bits for the Sign Industry

Sign shops routinely machine wood, aluminum, foam, and plastic, but each material has different cutting characteristics. No single router bit can solve every routing application, particularly when plastics are involved.

Choosing Router Bits for Plastics

As a starting point, plastics can be divided into two broad categories: flexible and rigid.

Flexible plastics typically use single- or double-edge O-flute tools in straight or spiral configurations.

Rigid plastics may be better suited to double-edge straight V-flutes, spiral O-flutes with hard-plastic geometry, or two- and three-flute finishing tools.

These recommendations are only starting points. Plastic grade, part geometry, cutter diameter, feed rate, spindle speed, and desired finish all influence final tool selection.

Smaller Diameter Tooling

Sign makers often require smaller-diameter tools to produce the tight radii associated with lettering and detailed shapes.

Cutter diameter has a major effect on achievable feed rate, but larger diameters are not automatically superior in terms of finish.

The use of micro-grain carbide combined with geometry designed for efficient chip evacuation has made smaller-diameter tooling increasingly effective for sign-industry applications.

Specialty Tools for Faster Finishing

Specialty router tools have also been developed to improve finished surfaces while reducing secondary operations, tool changes, and programming complexity.

Bottom Surfacing Tools

Most router bits are designed primarily around side-cutting geometry. During pocketing or lettering operations, the point geometry can leave visible swirl marks on the bottom surface.

Bottom-surfacing tools use a near-flat point with radiused corners to create a smoother and more visually consistent pocket floor.

Rout and Chamfer Tools

Rout-and-chamfer tooling combines a plastic-cutting straight flute with a 45-degree chamfering edge.

This allows a plastic part to be routed and a variable-depth edge chamfer to be applied during the same machining operation.

Figure 1 Solid Carbide Bottom Surfacing

Figure 2 Solid Carbide Rout and Chamfer

Tooling and CNC Routing

Advances in router tooling have followed the rapid growth of CNC routers and router tables throughout the sign industry.

These machines have improved the speed and accuracy of sign production while allowing intricate shapes and designs to be created with specialized programming software.

Modern tooling complements these machines with stronger tool materials and cutting geometries designed for specific workpiece materials.

Correct tooling alone, however, cannot compensate for poor machining practices.

CNC Machining Practices

• Maintain CNC equipment according to the manufacturer's recommendations, including proper lubrication of slides and drive systems.
• Check for play in the table and spindle mounting systems.
• Establish a maintenance program for collets, collet nuts, and tool holders.
• Consider replacing collets after approximately 600–700 hours of use.
• Maintain part rigidity through proper spoilboard and workholding techniques.
• Use correct colleting procedures to maximize tool rigidity.
• Maximize appropriate chipload to reduce unnecessary cutter wear.
• Select the shortest cutting-edge length capable of achieving the required depth of cut.
• Where practical, use straight-through tools with cutting-edge and shank diameters of the same size to reduce breakage risk.
• Maintain effective dust collection to evacuate gummy plastic chips from the cutting area.

Conclusion

The sign industry requires tooling capable of machining a wide range of materials and part geometries.

For plastic routing, success depends on matching cutter geometry and tool material to the specific plastic and machining environment.

Specialty tools can also reduce secondary operations and cycle time, but the best results still depend on sound CNC maintenance, fixturing, chip evacuation, and cutting practices.