How Do I Determine Which Router Bit I Need?

Introduction to Common Woodworking Router Bits

Mastering Woodworking Mastery: An In-Depth Exploration of Common Woodworking Router Bits and Their Versatile Applications in Crafting Woodwork Excellence.

1. Overview

   (1) Introduction

   A woodworking router bit is a rotating cutting tool with one or more teeth. By moving relative to the workpiece, the teeth intermittently remove excess material from the workpiece. Router bits are widely used in fine woodworking to process flat surfaces, shape contours, create grooves, chamfers, dadoes, and engraving, among other tasks. Compared to router bits used for cutting metal, woodworking router bits typically have larger rake and relief angles to obtain sharp cutting edges and reduce cutting resistance. Another characteristic is that they have fewer cutting teeth, providing more chip clearance space. In addition to tool steel and alloy steel, woodworking router bits are also commonly made of carbide to enhance productivity and tool life. As shown in Figure 1.

 Figure 1 Various Common Forms of Woodworking RouterBits

Figure 1

 (2) Composition of Woodworking Router Bits

   ① Chip Ejection Slot/Blade (Figure 2): The groove on the router bit is a deep spiral groove along which the cutting edge, known as the blade, travels. The blade cuts the material, and the resulting chips are pushed out through the chip ejection slot while the router bit rotates. Each chip ejection slot typically has one blade, although some cutters have two blades per slot. Generally, chip ejection slots and blades can be interchangeable. Router bits can have one or multiple blades, with 2, 3, and 4-blade configurations being the most common. Typically, the more teeth a blade has, the faster it can remove material. For example, a 4-tooth blade cuts material twice as fast as a 2-tooth blade.

 Figure 2

  ② Helix Angle: Most router bit grooves are helical. If the chip ejection slot is straight, the entire blade immediately impacts the material, causing vibration and reducing accuracy and surface quality. Setting the chip ejection slot at a certain angle allows the blade to gradually enter the material, reducing vibration, and improving accuracy and surface quality.

   ③ Shank

   a) The shank is the cylindrical (non-grooved) part of the tool, and it is the crucial part that connects the router bit to the router machine. It allows users to securely fasten the router bit to the collet or clamping device on the router machine for cutting, engraving, shaping, and other woodworking tasks. The shank serves as both the connecting hub for the tool and the conduit for transmitting power from the router machine to the router bit. This enables the router bit to rotate and perform cutting operations. Shanks are typically available in 1/2-inch and 1/4-inch sizes (see Figure 2), as well as metric sizes like 6mm and 12mm, which are commonly used in handheld routing, CNC machining, and other woodworking applications.

   b) The diameter of the shank should be equal to or larger than the diameter of the cutting tool. If the cutting tool has a diameter equal to or less than 1/4 inch, a 1/4-inch diameter shank should be used. For cutting tools with diameters between 1/4 inch and 1/2 inch, a 1/2-inch diameter shank is appropriate. If the collet of the router allows, larger diameter shanks, such as 3/4 inch, can be used, enhancing machine safety. Most CNC routers permit the use of larger diameter shanks, improving machine safety. All cutting tools should have a precisely machined shank, as any unground shank cannot mate well with the collet.

   c) The shank should have sufficient length to fully utilize the entire working face of the collet. If the lower part of the collet only clamps the top of the shank, it will inevitably result in router bit breakage, spindle and collet wear. When clamping the tool, care should be taken to avoid clamping chips and ensure that the clamping depth meets the requirements. For example, for a 1/2-inch shank (12.7mm), the clamping depth should be 24mm to ensure its proper load-bearing capacity. Generally, the depth of the shank should be at least 4/5 of the shank length.

   Figure 3 1/2-inch and 1/4-inch Shanks

(3) Cutting Diameter of Woodworking Router Bits

The cutting diameter of woodworking router bits is determined by the width of the slot to be machined and the thickness of the material. It is not advisable to use a 1/4-inch diameter router bit to cut materials with a width greater than 3/4 inches. Using a router bit with a larger diameter is more reasonable. It is important to note that using router bits with longer cutting edges reduces the risk of router bit breakage.

(4) Specification of Woodworking Router Bits

In English specifications, 1 inch is equal to 25.4 millimeters. Therefore, 1/4 inch is equal to 6.35mm, and 1/2 inch is equal to 12.7mm. For example, “Straight Bit 1/4×1/2” indicates a shank diameter of 6.35mm and a blade diameter of 12.7mm. Similarly, “Roundover Bit 1/2×1-1/8” indicates that the roundover bit produces a circle with a diameter of 28.575mm for the rounded edge.

2.Classification of Woodworking Router Bits (Categorized by Function)

Face Molding Router Bits(Figure 4)

Face molding router bits” are a type of woodworking router tool used to create various decorative edges and profiles on the surface of wood. These bits are typically installed on a woodworking router, and by rotating the bit and moving the router along the edge or surface of the wood, it’s possible to easily cut different shapes of edges.

The design of face molding router bits is diverse, allowing for the creation of various edge   types such as curved edges, beveled edges, intricate decorative profiles, and more. These bits are typically made from high-speed steel or hard alloy to ensure effective cutting and a long lifespan.

Figure4 Face Molding Router Bits

Flush Trim Router Bits(Figure5)

Flush trim router bits, also known as flush-cut router bits, are woodworking router accessories designed for the precise trimming and smoothing of edges, surfaces, or laminates so that they are flush with the surrounding material. These bits are commonly used to achieve a clean and uniform edge or surface finish in woodworking projects.

Key features and uses of flush trim router bits include:

①Flush Trimming:

These bits have a bearing on the tip or at the base, which acts as a guide. The bearing follows the template or existing edge, while the cutting flutes remove excess material, making the edge or surface flush with the template or adjacent material.

②Template Routing:

Flush trim router bits are often used in conjunction with templates or patterns to duplicate complex shapes or contours. The template is positioned on top of or alongside the workpiece, and the bearing on the bit follows the template, resulting in an identical shape on the workpiece.

③Edge Banding:

They are frequently used for trimming edge banding materials, such as veneer or laminate, to ensure that they are perfectly flush with the substrate.

Laminates and Overlays: These bits are ideal for trimming laminates and overlays to size, providing a smooth and even edge where the overlay meets the base material.

Figure5 Flush Trim Router Bits

Cabinet door router bits(Figure6)

“Cabinet door router bits” are specialized woodworking router tools designed for crafting cabinet doors. They are indispensable tools in the production of cabinets and furniture, used to cut and decorate various components of cabinet doors, allowing for the creation of different styles and designs. They can be employed to produce a variety of cabinet door styles, including flat-panel doors, raised-panel doors, arched doors, frame-and-panel doors, and more.

Different types of router bit designs enable woodworking craftsmen to customize the appearance and style of cabinet doors. These bits typically include decorative edge designs such as tongues, grooves, profiles, and cutouts, adding intricate decorative elements to cabinet doors. Typically, in the process of crafting cabinet doors, the door panel’s shape is first cut using panel bits, followed by the use of different types of router bits to add decorative edges or contours. These bits are often used in multiple steps to complete the entire cabinet door manufacturing process.

Figure6 Cabinet door router bits

Mortise and Tenon Router Bits(Figure7)

Mortise and Tenon Router Bits are essential woodworking tools used for creating strong and precise joints in woodworking projects. These bits come in pairs, with one designed for cutting a mortise (a rectangular hole), and the other for cutting a matching tenon (a projecting piece). They are commonly employed in furniture making and carpentry for constructing sturdy and durable joints, ensuring that pieces of wood fit together seamlessly and securely. Mortise and tenon joints are renowned for their structural integrity, making these router bits invaluable in crafting high-quality woodwork.

Figure7 Mortise and Tenon Router Bits

Ball End Router Bits(Figure8)

Ball End Router Bits are specialized cutting tools used in woodworking and machining. These bits have a unique spherical or ball-shaped tip, which allows them to create rounded or curved profiles, contours, and grooves in the material being worked on. They are often used for tasks such as carving, engraving, and sculpting, as well as for adding decorative edges and details to woodworking projects.

Figure8 Ball End Router Bits

Bullnose Router Bits(Figure9)

Bullnose Router Bits are specialized woodworking tools designed for adding a rounded, semi-circular profile to the edges of wood pieces. These bits create a smooth, curved edge that resembles a half-circle, making them ideal for finishing the edges of tabletops, shelves, and other furniture components. Bullnose router bits are commonly used to create a decorative and ergonomic edge, which not only enhances the appearance of woodworking projects but also provides a comfortable and safe edge for users.

Figure9 Bullnose Router Bits

Chamfer Router Bits(Figure10)

Chamfer Router Bits are woodworking tools designed for creating beveled edges or chamfers on the corners or edges of woodwork. These bits typically feature angled cutting edges that allow for precise and controlled removal of material at a specific angle, commonly 45 degrees.

Chamfer router bits are used to add decorative edges, create smooth transitions between different surfaces, or remove sharp corners for safety and aesthetics. They are versatile tools that find applications in a wide range of woodworking projects, including furniture making, cabinetry, and trim work, and they can enhance both the appearance and functionality of the finished woodwork.

Figure10 Chamfer Router Bits

Cove router bits(Figure11)

Cove Router Bits are woodworking tools designed for shaping concave profiles or coves into the edges or surfaces of wooden pieces. These bits have a curved cutting edge that creates a semi-circular or curved groove when used with a router. Cove router bits are commonly used for decorative purposes, adding elegant and ornamental details to woodworking projects.

They can be used to create trim work, moldings, and various types of decorative edges on furniture, cabinetry, and other wooden items. These bits come in various sizes, allowing woodworkers to achieve different cove depths and profiles to suit their specific design requirements. Cove router bits are essential tools for enhancing the aesthetics of woodworking projects.

Figure11 Cove router bits

Dovetail Router Bits(Figure12)

Dovetail Router Bits are specialized cutting tools used in woodworking to create dovetail joints, which are known for their strength and aesthetic appeal. These bits have a unique shape with angled cutting edges that allow for the creation of interlocking, wedge-shaped joints.

Dovetail joints are commonly used in cabinetmaking, drawer construction, and other woodworking applications where a strong and visually appealing connection between two pieces of wood is desired.

Dovetail router bits come in various sizes and angles to accommodate different dovetail joint styles, such as through dovetails and half-blind dovetails. They are essential tools for woodworkers looking to produce high-quality and sturdy joinery in their projects while adding a touch of traditional craftsmanship to their work.

Figure12 Dovetail Router Bits

Handrail Router Bits(Figure13)

Handrail router bits are specialized cutting tools used in woodworking to create decorative and functional handrails for staircases, balconies, and other architectural elements. These bits have a unique profile that allows woodworkers to shape and detail the handrail’s top and bottom edges.

They are designed to create precise and elegant profiles, which not only provide a comfortable grip but also enhance the overall appearance of the handrail.

Figure13 Handrail Router Bits

Joinery Router Bits(Figure14)

Joinery Router Bits are specialized cutting tools for woodworking, used to create a variety of precise and robust connection joints for assembling wooden components. These bits are designed to produce specific profiles and cuts that enable woodworkers to create tight-fitting joints for furniture, frames, and other woodworking projects.

Joinery Router Bits come in various shapes and sizes to accommodate different joint types, including dovetail joints, mortise and tenon joints, box joints, lock miters, finger joints, tongue and groove joints, rabbets, and drawer locks.

These bits are valuable tools for woodworkers, allowing them to craft strong and accurate joints, enhancing the structural integrity and appearance of wooden projects. Typically, these bits are used with a router table or handheld router to achieve precise and consistent results in joinery work.

Figure14 Joinery Router Bits

Keyhole Router Bits(Figure15)

Keyhole Router Bits are specialized cutting tools used in woodworking and other applications to create keyhole-shaped slots or grooves in materials, typically wood. These bits feature a distinctive profile resembling a keyhole or elongated circle with a straight edge.

They are commonly employed for hanging items like pictures, mirrors, and shelves securely on walls by sliding onto screw or nail heads. Keyhole router bits are versatile tools, not only serving a functional purpose in wall mounting but also offering decorative and creative possibilities in various woodworking and crafting projects, making them valuable additions to a woodworker’s toolkit.

Figure15 Keyhole Router Bits

Rabbeting Router Bits(Figure16)

Rabbeting router bits are specialized cutting tools used in woodworking to create rabbets, which are shoulder or step-shaped recesses, along the edges or surfaces of wood.

These bits come in various sizes and profiles, allowing woodworkers to customize the width and depth of the rabbet cut to suit their specific project requirements. Rabbeting router bits are commonly used for tasks like creating joints, housing panels, and adding decorative edges to wooden pieces.

They are versatile and essential tools in woodworking, enabling precise and controlled rabbet cuts to enhance both the structural integrity and aesthetic appeal of woodworking projects.

Figure16 Rabbeting Router Bits

Raised Panel Router Bits(Figure17)

Raised Panel Router Bits are specialized woodworking tools designed to create raised panel profiles on cabinet doors, furniture, and decorative elements. These bits feature a unique design with a large, vertical cutting surface that, when used with a router, produces a raised, three-dimensional panel.

Typically employed in conjunction with a router table for precision, Raised Panel Router Bits are available in various styles, including traditional, ogee, and shaker profiles, enabling woodworkers to achieve diverse decorative effects.

These bits are indispensable for adding depth, dimension, and intricate detailing to woodworking projects, elevating their visual appeal and contributing to professional-quality craftsmanship in cabinetry and furniture construction.

Figure17 Raised Panel Router Bits

roundover router bit(Figure18)

A roundover router bit is a specialized cutting tool used in woodworking to create a rounded edge or profile on the corners or edges of wooden pieces. These bits have a rounded cutting edge that can produce a smooth, semi-circular curve when used with a router.

Roundover router bits are commonly used for easing sharp edges, adding a decorative and tactile element to wooden surfaces, and reducing the risk of splinters or injuries.

They come in various sizes, allowing woodworkers to achieve different roundover profiles and degrees of curvature, making them versatile tools for enhancing the safety and aesthetics of woodworking projects.

Figure18 roundover router bit

slot cutter router bit(Figure19)

A slot cutter router bit is a specialized woodworking tool designed for cutting slots or grooves in various materials, particularly in wood. These bits are equipped with sharp blades or cutting edges that are used to create precise and uniform slots of different widths and depths.

Slot cutter router bits are commonly employed for tasks such as creating dadoes, grooves for joinery, and decorative flutes or channels in woodworking projects.

Figure19 slot cutter router bit

T-Slot Router Bits(Figure20)

  • Slot Router Bits are specialized cutting tools used in woodworking and machining to create T-shaped slots or channels in materials, commonly in wood, plastic, and metal. These bits have a unique profile with a straight edge at the bottom and a perpendicular, T-shaped groove above it.
  • T-Slot Router Bits are often utilized for constructing fixtures, jigs, and workbenches, where T-slots are essential for securing and adjusting components. They are valuable tools in precision woodworking and engineering applications, providing versatility for designing and building customized workholding and clamping systems.

Figure20 T-Slot Router Bits

3、Formation of Woodworking Router Bit Chips

   There are various types of router bits, and understanding how chips are formed is crucial for using them effectively. When router bits rotate, the material to be cut is fed into them for cutting. Each tooth of the cutter removes a small piece of material, and the size of the cut material depends on several variables.

   (1) Surface Cutting Speed (Vc): This is the speed at which each tooth passes through the material when the tool rotates. This should not be confused with the feed rate. This value is also known as “tangential speed.”

   (2) Spindle Speed (S): This is the rotational speed of the tool, measured in revolutions per minute (rpm). Typical values range from hundreds of rpm to tens of thousands of rpm.

   (3) Tool Diameter (D): The diameter of the cylindrical part of the tool.

   (4) Number of Teeth (z): The number of teeth on the router bit.

   (5) Feed per Tooth (Fz): This is the distance the material is fed into the tool when each tooth rotates. This value represents the maximum depth of cut for each tooth.

   (6) Feed Rate (F): This is the speed at which material is fed into the tool.

   (7) Cutting Depth: This is the depth below the surface of the material where the tool operates. It determines the height at which chips are produced. Typically, the cutting depth will be less than or equal to the diameter of the cutting tool.

   Usually, we need to know three parameters: spindle speed (S), feed rate (F), and cutting depth to determine how to select the tool for cutting material effectively.

Spindle speedFeed speed
Looking at the formula for spindle speed S, it can be seen that larger tools require lower spindle speeds, while small tools may run at high speeds.The formula for feed rate F shows that increasing S or z provides a higher feed rate. Therefore, the master can choose a tool with the highest number of teeth that can still cope with the chip load.

4. Milling Modes of Woodworking Router Bits

   Common woodworking router bits have two milling modes: conventional milling and climb milling. Router bits can perform cutting in two directions known as climb or up milling and conventional or down milling.

   (1) Climb Milling(Figure20):

Cutting starts from zero thickness and increases to the maximum thickness. Initially, the tool does not cut but glides over the material surface until the teeth suddenly engage and start cutting. This can cause material deformation (point A in the diagram) and leave a poor surface finish on the material.

Figure20 Climb Milling

  • Conventional Milling(Figure21): Each tooth engages the material at a certain position, and the width of the cut decreases from the maximum to zero. The chips are formed behind the cutter, making it easier to clear them. The blades do not rub against the material, so the tool life is longer.

Figure21 Conventional Milling

5. Criteria for Changing Woodworking Router Bits

   (1) Under normal circumstances, if there are five notches in the material within 1 meter of cutting, it indicates that the tool cannot continue to be used.

   (2) If the cutting sound is very heavy or screeching, it indicates that the tool is not in a normal processing condition. A brief analysis can be performed, and if the tool quality, tool clamping, and cutting parameters are ruled out as issues, it can be determined that the tool is worn and needs to be replaced.

   (3) The wear of the tool can be judged by the machine tool’s motion during machining. If machining parameters, cutting amounts, and other settings are reasonable, but the machine tool vibrates significantly and emits a buzzing sound, it can be determined that the tool is severely worn and needs replacement.

6. Selection of Geometric Angles for Woodworking Router Bits

   The choice of angles for router bits should be determined based on the characteristics of the workpiece material. For workpieces with high hardness that require high cutting edge strength, the front angle of the router bit should be reduced to increase the wedge angle while keeping the back angle constant. When hand-feeding, the front angle of the router bit can be increased to reduce effort. Recommended front angle γ values based on workpiece properties are as follows: for machining soft materials, γ = 25°–35°; for machining hard materials, γ = 10°–25°. The variation range of the back angle α is not large and is generally selected within the range of 10°–15°.

  • Overall Principles for Selecting Woodworking Router Bits

   The selection process for woodworking router bits generally considers the following aspects:

   (1) Part Shape (Considering Machined Surfaces): Machined surfaces can be flat, V-shaped, grooved, threaded, etc. Different types of tooling are used for different machined surfaces. For example, roundover bits can be used to mill convex surfaces but not concave surfaces.

   (2) Material: Consider aspects such as cutting processability, chip formation, hardness, and alloy elements present in the material. Tool manufacturers typically categorize materials as various types of wood, wood-plastic materials, straw-based composite boards, veneer boards, integrated materials (including bamboo-based integrated materials), melamine-impregnated paper veneer boards, PVC veneer boards, ALO, laminate flooring, acrylic (ACRYLIC), etc.

   (3) Machining Conditions: Machining conditions include machine tools, fixtures, workpiece system stability, and tool clamping. Tool selection should take into account factors such as spindle speed, machine tool size, maximum fixture opening, and tool clamping tightness based on machining conditions.

   (4) Machine Tool-Fixture-Workpiece System Stability: This requires an understanding of available machine tool power, spindle type and specifications, machine tool age, and consideration of the tool’s overhang length and axial/radial runout.

   (5) Machining Categories and Subcategories: This includes side milling, face milling, contour milling, etc., and requires tool selection based on the characteristics of the tool’s application. In general, for low-density and low-hardness board materials, choose ordinary router bits. For materials with nails and other elements that cause significant tool wear, choose ordinary router bits. For materials that are rarely used, choose ordinary router bits. For high-density and high-hardness board materials, choose high-quality router bits. For materials such as acrylic sheets and engineered stone, choose premium router bits.

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