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Router Bits Buying Guide

With the blistering array of styles, profiles and shank sizes available, it is easy to forget that the router bit is the most important part of any routing set up. The quality and design of the bit will have an enormous impact on the resultant finish. With the development of computer aided design and manufacturing router bits are now safer to use, better balanced and are more durable.

Anatomy of a Router Bit

Anatomy of a Router Bit

Unless they are bearing guided, router bits have no moving parts, but it would be foolish to think of them as simple cutting tools. There are a number of very important design elements to a router bit that determine how well it performs.

The bit can be split up in to two distinct parts; the shank and the cutting head. The shank of the bit is the only point of contact between the bit and the router and this must be smooth, straight and of correct diameter for the router collet to clamp it correctly and securely. The entire router bit is usually machined from a single piece of steel meaning the shank is integral to the bit head.

Most router bit heads have tungsten carbide tips brazed on to them although some bits may be machined from high speed steel (HSS) or carbide and feature integral cutting edges. The cutting edges should run at a slight angle known as the shear angle. This allows the router bit to cut in a similar fashion to a plane in that the wood is shaved, rather than chipped, away.

As well as sitting at an angle down the body of the bit, the tips also sit at an angle to the axis of the bit. This is referred to as the hook angle and assists with the chip clearance when cutting. The relief angle is, in effect, the bevel angle of the cutting tips. This angle is important as it prevents the bit from scorching the wood during cutting.

Router bits today have an anti kick back design. Kick back is caused when the cutting edge bites too deeply into the work piece and is unable to complete the cut. This results in the work being thrown by the bit in the direction of its movement which is contrary to the direction of the feed. In certain circumstances, this can cause injury to the operator.

The anti kick back design features a shoulder set in front of the cutting edge that limits the depth of cut. The deeper a bit attempts to cut, the higher the risk of kick back. ©

Types of Router Bits

Straight

Straight bits are possibly the most versatile type of bit. As well as being used for putting a straight, square edge on work pieces, these bits can also be used for cutting rebates, grooves and dadoes. Used in conjunction with a guide bush, straight bits are often the bit of choice when following a template. Straight bits can be used in a router table for jointing work also. ©

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Joinery

Joinery router bits are those bits that shape all or part of a joint. These include rail and stile bits for panelled doors, tongue and groove bits, glue joint bits and mitre joint bits. Some types of joint require two bits that cut opposite profiles such as the rail and stile and the tongue and groove. Other bits are capable of cutting both sides of the joint and require only that the two pieces being joined are presented to the bit in different positions. Joinery router bits are usually designed for use in a router table only. ©

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Grooving

Grooving bits produce a V-shaped channel and can be used for lettering, etching designs and giving a jointed tongue and groove look to a solid panel. V-groove bits can also be used to create bird's mouth joints and putting a chamfered edge on square stock. ©

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Lettering & Template Following

Lettering and template following bits are designed to give a smooth finish with minimal tear out regardless of the shape of the cut. Some of these bits have bearing guides attached whereas others require the use of a guide bush. These bits give a decorative etched, carved or engraved look depending on the profile. Smaller diameter bits are ideal for freehand work, larger diameters must be used in a router table. ©

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Plunge Profile

Plunge profile bits can be used for adding detail and designs such as creating a panelled design on a plain door. Unlike with bearing guided bits, the plunge capability allows the bit to begin the cut away from the edge of the board. This is particularly useful when you need to add a design to the middle of the board. Plunge profile bits can be used with a guide bush for edge and template work, if required. ©

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Edge Profile

Edge profile bits are used for cutting profiles around the edges and on the faces of work. This type of bit comes in all shapes and sizes with some featuring an attached bearing guide and others requiring the use of a guide bush. The small diameter bits may be used freehand in a router, the large bits must be used in a router table. The large bits are used for creating architectural mouldings such as skirting boards, architraves, coving, dado and picture rails. ©

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Rebating

A rebating bit is used to cut a rabbet which is a long recess on the edge of a board. Used for jointing and other projects such as creating inset doors and drawers, rebating bits come in many different sizes. These bits feature bearing guides and the depth of the rebate produced is determined by the diameter of the bearing in relation to the diameter of the bit; the smaller the difference in diameters, the smaller the rebate will be. Some rebate bits are supplied as one bit with a number of differently diametered bearings giving the option of mulitple sizes of rebates from one bit. ©

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Slotting

Slotting bits are large diameter, thin bits that produce slots and grooves. Used for cutting grooves, slots and rebates, biscuit jointing and also for tongue and groove joinery, slot bits are usually a cutting head with a guide bearing mounted on an arbor. These bits may be used freehand in a router although it is recommended that the larger diameter bits are for router table use only. ©

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Raised Panel

Some of the largest router bits available, raised panel door bits are used for putting the wide sweeping profiles on the panels in the centres of the doors. Due to the large diameter of the bit, these are for use only in a router table. There are variations of this bit available; vertical raised panel door bits are ideal for use with a lower powered router as these do not have the physical mass or large diameter of the standard bits. The raised panel door bits with undercutting are used for thicker panels and these produce a 6mm lip around the panel that fits in to the groove in the frame of the panel door. ©

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Trimming

Used for trimming laminate and veneer facings and edgings, trimming bits are bearing guided to give a perfectly flush finish. Designed to cut smoothly without splintering, trimming bits are available to give either a square or chamfered edge. Generally mounted on 1/4" shanks, trimming bits feature bearing guides and are designed for free hand use but may be used in a router table if required. ©

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Features to Consider When Buying a Router Bit

Features to Consider When Buying a Router Bit

1. Shank Size

For many router users, the choice of shank size is not an option. However, if your router comes with more than one size of collet, it is worth considering which size shank to opt for. The shank diameter on a router bit does have an influence on how the bit performs. The larger the shank diameter, the less likely the router bit is to vibrate during cutting. Excessive vibration of the bit will give a poor cut. This does not mean that you will always get a poor cut from a 1/4" shank bit though. Larger diameter cutting heads as well as longer length cutting heads can also suffer from vibration. When you have the option, select a bit with the largest shank size your router will accept. ©

2. Type of Material Being Cut

The type of material you are intending to cut should influence your choice of bit. Tungsten carbide tips are excellent for cutting softwoods, hardwoods, plywoods and even some plastics. The tips on these bits remain sharper much longer than solid high speed steel bits which become dull very quickly. For exceptionally abrasive materials such as particle board and MDF, solid carbide bits are preferable as they are even harder than tungsten carbide tipped bits and take even longer to dull. When selecting a bit consider what you will be cutting and how much cutting you will be doing. ©

3. Freehand or Table Mounted Routing?

The diameter of a router bit gives a good indication of whether it can be used freehand or requires the use of a router table. Router bits with smaller shank diameters such as 1/4" and 8mm have correspondingly small bit heads and are ideal for use freehand, as are 1/2" shanked bits with small diameter cutting heads. 1/2" shanked bits with larger diameter cutting heads like those used for face profiling or joint creation should only be used in a router table. ©

4. Bearing Guided

Bearing guided bits allow the cutting of a straight or curved edge without the need for a router fence. The bearing references the face of the work allowing the bit to follow the shape of the edge precisely. Bearing guides are also useful when using a template as the bearing will follow the template while the bit shapes the work. Bearing guides eliminate the need for guide bushes and specialist base plates. ©

5. Flute

The flute is the part of the router bit that makes the cut. The number of flutes a router bit has affects both the speed and the cut. A single flute bit cuts very quickly, but leaves a rougher finish than a bit with two flutes would. The higher the number of flutes, the slower the router bit cuts but the smoother the finish will be. ©

Tips From the Experts

1. Never attempt to cut a full profile in one pass, this will result in a poor finish. By taking a number of passes to form the profile, removing a small amount of stock each time, the resultant finish will be much smoother and far more professional looking. ©

2. When making freehand straight cuts, use either a bearing guided bit or a router fence to ensure the cut is perfectly straight. ©

3. Featherboards will help keep the work piece flat to the table, flat to the fence and, more importantly stop the workpiece from flying backwards as a result of kickback. ©

Brands

Tornado

Tornado router bits are produced using the very latest manufacturing technology. Computer controlled design and production ensures that every bit is geometrically correct and perfectly balanced to give the best possible performance. Each bit incorporates an anti-kickback design that is certified to the strict German DIN 847-1 standard. These best selling bits are also quality approved by HBG in Germany.

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Sharpening & Maintenance

Sharpening

Dull router bits will tear and even scorch the wood during cutting. If this starts to happen then the bit needs sharpening. ©

Router bits may be sharpened by hand using a small diamond stone or file. ©

Care should be taken not to change the shape of the cutting edge as this will effect the geometry and balance of the bit and will result in a poor cut. ©

Maintenance

Router bits are prone to rust. When not in use, a coating of light tool oil will protect them or store them individually in corrosion inhibiting bags. ©

Ensure the shank of the bit is clean and smooth at all times. ©

Any rust or corrosion can be removed from the bit using 0000 wire wool. ©

Remove any debris and resin from the bit after use. Some specialised cleaning products offer protection against resin build up and are ideal if you rout resinous woods such as pine. ©

Replace bearings as soon as they stop rotating freely and start dragging. ©