How to Use a Router Power Tool
How to Use a Wood Router
How to use a router is an impossibly broad subject for one article; entire books can't cover everything there is to know. The problem is that a wood router is such a versatile power tool and can perform so many different tasks. The router itself can range from a small 3/4 HP tool for trimming laminate to a massive 3 1/2 HP plunge router that will handle the largest router bits on the market.
Nevertheless, it is possible to cover the basics of using a wood router properly and safely and a few basic tips will go a long way toward learning all the intricacies of what a router is capable of.
Towards that end, let's start with the cutting edge of a router—the router bit that does all the work.
Choosing a Router Bit
Router bits are available in HSS (High Speed Steel) and with a carbide cutting edge. Carbide bits generally cost more (up to twice as much) but last 10 to 25 times as long. They retain their sharp cutting edges much longer, resulting in a cleaner cut, and are indispensable when cutting man-made panels such as plywood or particle board. The glue in plywood will dull even a new HSS bit after making only a few short cuts, and particle board is even worse. Carbide router bits are highly recommended for any router work being done.
In general, router bits are either used to make cuts in the center of the wood or to produce a decorative edge. Bits designed for those beautiful edge treatments will nearly always have a section that rides on the edge of the wood as a guide, and a rotating bearing is much preferable to a simple extension of the shaft. If the rapidly rotating shaft is held against the wood, it is all too easy to leave burn marks behind; the bearing guide will not as it does not rotate with the shaft.
Common Router Bits
- Straight bits. Simple straight bits that will cut a square groove in the wood. Common sizes range from 1/4" to 3/4", but exact sizes for plywood are available as well. Remember that 3/4" plywood is not 3/4" thick; it is 1/32" less than that (23/32") and router bits are available in that exact size as well as the correct sizes for 5/8" and 1/2" plywood.
- Rabbeting bits. Designed to cut a square groove at the edge of the wood for gluing purposes. A rabbeting bit will always have a guide to keep it from veering into the workpiece (make sure it is a bearing type).
- Roman Ogee. A common and popular bit to produce an "S" shaped cut at the edge of the wood.
- Chamfer Bit. Usually with a guide, the bit is to provide a bevel at the edge of the work.
- Flush Trim Bit. Used to trim the edge of one material flush with another; the most common use is to trim laminate (formica) coverings. This bit can either leave the edge of the formica straight and flush with the wood it is glued to or trimmed at a 45° angle.
- Raised Panel Bits. Used to produce the raised panels on cabinetry. Most of these are quite large and should only be used in conjunction with a router table and a large, powerful router.
- Other Specialty Bits. There are literally hundreds of styles of router bits available for special uses. Keyhole cutters to make a slot to hang onto a screw or nail. Various joinery bits for special wood joints such as dovetails or fingerjoints. Roundover, cove and edge beading bits. Bits to produce a "V" or "U" groove in the surface of the wood. The list is almost endless.
A major concern when choosing a bit or bit set is the shank diameter. Routers typically come with chucks that accept either ¼" or ½" shank bits. The larger ½" router will often have an adapter that will accept ¼" bits, but the reverse is not true. Make sure that your router can use the bit you have chosen. The larger shank size is preferable as it will not vibrate or chatter as much, but ¼" shank bits will work very well for all but the largest bits, such as raised panel or moulding bits.
Setting the Router Bit in the Router
With the bit chosen, it must be inserted into the router and the correct depth set. Bits should be inserted as far as possible into the tool and the "chuck" tightened firmly. Don't try to use the router with only a short length of the bit shank actually in the tool; it can all too easily come out and cause serious injury.
With the bit fastened securely into the router, it is time to set the depth of cut that the bit will produce. Start by changing the depth adjustment on your router until the very tip of the bit is at the surface of the base plate; just to the point that the bit would just barely touch the wood if the router were used at this setting. This can be accomplished by either setting the router upright on a piece of scrap wood and lowering the bit until it just touches the wood or by setting the router upside down and "raising" the bit until it is even with the baseplate. In this case, some kind of flat material should be used to verify it is even with the baseplate; simply eyeballing it won't give a good indication. The pictures below show this step.
Snug the adjustment lock and set the measuring wheel or device to zero, indicating that the bit is at exactly zero depth. Loosen the lock and, without changing the zero adjustment, move the bit the desired amount for the correct depth of cut. Tighten the adjustment lock once more.
Some bits for edge decoration will require a slightly different technique as the pilot bearing on the bottom of the bit interferes with getting a true zero setting. In these cases the depth will have to be set with the router upside down, measuring from the baseplate to the end of the cutting surface on the bit. A steel ruler, the type sold in office supply stores, is invaluable here. Make sure that the ruler is sitting perpendicular to the base of the router and not tilted when measurements are being taken.
While most routers are capable of adjusting a bit to a depth of one inch or more, this is far too deep a cut to attempt. The maximum depth of cut that should be made will depend on many factors, including the size of the bit (a ¼" straight bit can be set deeper than a ¾" bit), the type of wood being used, and the size and power of the wood router as well as other factors. A good rule of thumb to start with is to set the depth to no more than 3/8" for straight bits. If the router motor bogs down or does not cut smoothly, decrease the depth somewhat. Additional passes can be made at ever increasing depths, removing no more than 3/8" of material at one time, until the full depth is reached. Edge bits, of course, will need to be set to the full depth necessary so that the entire cut can be made in just one pass.
Multiple Passes With Edge Bits
This technique seldom works because of the design of the bit. Intricate designs on the edge of the wood require that only certain sections of material be removed, with other areas left untouched or cut to a shallower depth. The very first pass may well take out material that a full depth pass would leave there, and can destroy the end product as a result. Although rabbeting bits can cut in successive passes, any decorative bit will almost always have to be used in one, full depth, pass.
Setting the Depth of CutClick thumbnail to view full-size
Using the Wood Router
Wood routers operate at a very high velocity, up to 25,000 RPM, and can catch and move the workpiece very easily. Smaller pieces of wood will need to be firmly clamped to a work table of some kind. A full sheet of plywood, longer boards or other large pieces are probably OK, but you could find a 12" square workpiece suddenly flying across the room if it is not clamped. Make sure that the clamps will not interfere with the movement of the router. In the photos below a Black and Decker Workmate bench has been used to clamp the workpiece and is ideal for just this sort of thing. The same high speed that can throw the workpiece around is absolutely going to throw sawdust, and lots of it. Wear safety glasses whenever using a router.
Similarly, the movement of the router across the workpiece must be guided. Freehand work with a router is possible with very shallow cuts, but it is very difficult to maintain the correct path. While edge bits have a guide built into them, use a guide for any work in the center of the workpiece. The guide in the photos below is quite old, and I have been unable to find another one, but it has been very useful over the years. It is actually a three piece straight edge that can be bolted together for a total length of over eight feet (full length of a sheet of plywood) and has clamps that slide into a T slot on the bottom to clamp to the workpiece. A similar guide is available from Amazon, although I have not used that model.
Mark the workpiece where the cut is to be made, showing both sides of the cut. The guide is to be placed ½ the diameter of the baseplate minus ½ the diameter of the bit from the upper side of where the cut is to be made. As an example, the workpiece is marked where a straight bit is to be used to make a dado cut, the router has a 6" diameter baseplate (common) and a ¾" bit is to be used. Half of the baseplate is 3" and half of the bit is 3/8"; the guide is to be placed at 2 5/8" (3" minus 3/8") from the edge of the dado cut.
With the router firmly held against the guide, slowly move the router into the workpiece. I like to make just the very start of a cut, back the router out and check that it is cutting in the proper place. It is easy to make a math error and clamp the guide in the wrong place, but a little more difficult to replace the wood routed out from the wrong place! Once the guide placement is verified as correct, continue the cut, always cutting from left to right. Moving the router from right to left will almost always result in a poor cut; the router will catch and pull away from the guide. Cutting from left to right the router will pull itself into the guide instead of away from it. The speed at which a cut is made is important as well; too slow and the bit will burn the wood, too fast and it will bog the router down and slow the bit rotation. Move the router just fast enough that it doesn't leave burned wood behind it but not so fast that the motor changes speed and slows down.
If cutting clear across a board, the far edge at the very end of the cut deserves special attention as it will likely splinter when the router exits the board. The solution is to carefully back the router up (or turn it off and wait until it stops turning) and cut the last little bit from right to left. Take extra care here as the router will try to curve away from the guide and make that last cut only as long as absolutely necessary. When edge bits are used and the cut is across the end grain of a board the same thing is done; the very last little bit is cut in the opposite direction to avoid splintering the board. An edge bit cutting with the grain and reaching the end won't splinter, but one cutting across the grain at the end of a board will.
This should get you well started with using a wood router. Power tools make a wonderful addition to any shop and the router is one of the more powerful and useful; with a little practice you can do practically anything with a router.
Cutting A Dado With A Wood RouterClick thumbnail to view full-size
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
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© 2012 Dan Harmon