Router Template Guides
Router template guides fit into the base of your router and direct it along the edge of a template. They can be used to accurately rout the edge of your stock to a specific shape, to rout cavities and mortises, or even to accurately bore positioned holes. They’re especially useful when making several parts that all need to be the same size, or when working with a complex shape.
Some routers use a proprietary guide system, while other manufacturers provide adapters or design their base plates to accept commonly available aftermarket guides. To determine whether a particular router accepts aftermarket guides, look at the hole in the base plate. If it has a 1-3/16" through-hole with a 1-3/8" diameter counterbore, it does.
Usually, guides are sold in a set that includes different sizes, but often you can find individually sold ones. Standard aftermarket guides include a ring nut that secures the guide to the base. Some specialty aftermarket base plates allow the use of standard guides with routers having original bases that use a proprietary system.
Guides are especially useful in a low-production environment where you are making a number of the same pieces. Creating a template for trimming a rough-cut piece of wood ensures that each piece will be identical to all the others. However, the templates themselves must to be thick enough to accommodate the depth of the guide. Remember this when planning your project, as different manufacturers and even different guide diameters can come in varying depths. Also, be sure to firmly attach the templates to your stock using double-sided tape or even screws if one side of your finished project won’t show. You can also use clamps if they don’t get in the way of the router.
You can use guides with a fixed-base router, but using a plunge router is more effective for routing internal cavities or shapes. This allows you to properly position the router first, and then plunge the bit into the wood.
Selecting the Router Bits
As indicated, guides are generally used with straight router bits. When routing edges, a standard straight bit with two flutes is adequate. When routing cavities or holes, up cut spiral bits are preferred, as they help clear waste from your work. The diameter of your bit has to be small enough to allow for clearance between the bit and the inside of the template guide. This prevents chips and sawdust from collecting.
Making Your Templates
With guides, your template will be larger or smaller than the finished size because of the offset between the cutting edge of the router bit and the edge of the guide that rides along the template.
You can calculate your offset by taking the guide-bushing diameter, subtracting the bit diameter and dividing by two.
For instance, using a 5/8" guide bushing and a 3/8" bit, the calculation is as follows:
5/8" – 3/8" = 2/8"
2/8" / 2 = 1/8"
The below chart gives the offset for common guide-bushing and router-bit diameter combinations. Note that some combinations won’t work because the router bit is too large to fit inside the guide bushing with sufficient clearance.
Router Bit Diameter | ||||
Template Guide | 1/8 | 1/4 | 3/8 | 1/2 |
5/16 | 3/32 | |||
3/8 | 1/8 | 1/16 | ||
7/16 | 5/32 | 3/32 | ||
1/2 | 3/16 | 1/8 | 1/16 | |
5/8 | 1/4 | 3/16 | 1/8 | 1/16 |
3/4 | 5/16 | 1/4 | 3/16 | 1/8 |
When creating a template, make your template either smaller or larger by the offset amount, depending on whether you’re routing outside or inside the template (for example, when doing inlays or mortises).
Aligning Your Template Guide
To ensure your guide is centered on the bit, use an alignment pin. Insert it into the router and screw the guide onto the router base. Loosen the router-base screws slightly and move the tip up so it’s snug in the guide opening. Ensure the guide is centered and tighten the router-base screws. Remove the pin.
You can also align by eye. For greater accuracy, keep the same edge of the guide against the template throughout the entire process.
Edge Trimming
Creating an interesting edge on tables, cabinet sides or other projects is easy to do with a jigsaw or bandsaw, but you’ll be left with saw marks to sand off. By cutting the shape close to the final size, and then using a template and a router to finish the job you get a consistent, smooth edge, which requires little additional work.
To do this, draw your pattern exactly to size. Decide which straight bit and guide you will use and calculate the offset (refer to the table above). If the shape is relatively straight or, at least, free of any sharp curves, cut the pattern to the exact size and simply shift it by the amount of the offset. If your pattern has deep curves you can use a compass or a pencil and a piece of wood that is the same width as the offset in order to draw the pattern. Keep your pencil perpendicular to the pattern edge at all times. Cut the pattern, sand it smooth and then secure it to the stock with clamps or double-sided tape.
Routing Mating Edges
When joining boards to make a wider surface, you can add some interest to the final piece by using different woods and by joining them using a wavy shape instead of a straight edge. Simply make one pattern and then use it to create a mirror image. Use an inlay bushing to ensure perfect alignment. This will account for the offset; otherwise, you would need to make two separate templates.
Routing a Cavity or Mortise
You can use a guide to rout a cavity or mortise using a simple template. Establish the required dimensions, draw the shape on your template and then add the offset. Cut the hole in the template and sand the edge smooth. Attach the template to your stock and, using a plunge router, position the guide in the hole. Plunge the bit into the stock and carefully rout out the waste. Use an up cut spiral straight bit and rout the waste in several steps.
Boring Holes
Repeatedly drilling a regularly spaced pattern using a drill or drill press can be tedious, as you have to measure and mark every hole. Instead, measure and mark once onto a template. Mark the location of the holes and bore them using a drill that matches the exact outside diameter of the appropriately sized guide. When all of these holes have been drilled, mount a cutter into the router that matches the hole size required in the workpiece. Attach the template to the stock, position the guide in a hole and plunge to bore the hole. Repeat the process on each hole.
Creating Inlays
Inlays can add an attractive element to your work, and using a guide makes the process easy. Create your pattern as described previously and rout the inlay recess with the inlay bushing installed on the guide. Then, remove the bushing and rout the inlay using the same template. The bushing automatically accounts for the offset when routing the recess and the inlay, allowing you to use a single template to cut a perfect-fitting inlay.
Michel Theriault