There are many things that wood routers can do and even more when you start adding the many accessories to them and one of these is something called router "bushing". In quick simple terms, what these bushings do is attach to the base of the router and allow the router bit to protrude through them which in turn makes them useful as a templating tool.
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The templates are the real secret to using router bushings ...
Router Bushings ...
come in a variety of sizes size openings and are attached to the base of handheld routers through various means, depending on what the router manufacturer has decided on. There are no real standards on router bushings or router bushing attachment bases. Likewise, the bits you might use in conjunction with specific bushing could be anything from a simple straight router bit, to a decorative bit.
A couple of more simple uses are using router bushings with a straight bit or an up or down spiral cutting bit in making holes, or even more commonly for making mortise cuts, which can later have their edges squared off, or they can be used in what are called "floating" or "loose" tenon wood joints.
One use for bushings is in making decorative panels for building interiors. In this case, large sheets of MDF material have routed groves cut in them, sometimes large squares, other times, things like wainscoting or similar designs. Much of this kind of work can be done using router bushings.
Finish carpenters who are cutting out recesses for door hinges often use router bushings. This allows them to use pre-made templates that are just size of the hinges they are installing and rather than using a chisel to cut these out, they can route them out with a router using a template and bushing and get a perfectly flat, perfectly fitting hinge recess in seconds. If you have examined hinges in the last decade or so, you may have wondered why many of them have rounded edges and not squared off edges as in the past. The reason for this is so that templates can be used with routers to cut the recess and of course, the corners of the recesses are slightly rounded, so now many of the hinges are cut the same so they make a perfect fit. Of course, if you are using square sided hinges, it's a simple job to just square off the corners with a wood chisel.
One of the special uses of bushings in with something called "Inlay Kits" which are a modified form of the bushing with 2 sizes and a matching router bit. The purpose of these kits is that with the use of a template of any size of the shape, you can use that template with one of the sizes of the bushing to carve out a portion of wood. Then using the same template but this time with the smaller bushing size, you can etch an outline of that original piece you carved out and the result is a perfectly matching insert that can then be glued into your wood for either and decorative or functional effect.
Setting Wood Router Bit Speeds ...
is often concerning those who are new to woodworking and working with wood routers. There are no real specific rules that apply, but more just some common sense guidelines that most people would adhere to anyway.
As we all know router bits come in 2 size shanks 1/4 inch and 1/2 inch. In many case bits with smaller cutting knives are available in either size, so this would be like small round over bits, smaller decorative Ogee bits, Smaller spiral up or down cutting bits and so on. What is NOT available in 1/4 inch shank bits are the much larger bits like some jointer bits and door making bits and larger edging bits. Smaller cutting bits can be used in any wood router, large cutting bits can only be used in larger wood routers, usually 2hp or more, that come with both size collets.
The "theory" is that router bits will perform best when they can be driven at high speed. This allows the cutting edges to cut quicker which means less tearing of the wood, BUT there are exceptions and safety considerations to follow.
Larger size router bits need to be driven at a lower speed - and that will need to be determined by the user, depending on the size of the router bit. With these bits is best to initially start at a slower, then speed up the router motor, often to half or two-thirds speed to what you feel is a comfortable speed for that bit, then leave it there, or make adjustments up or down as needed.
NOTE - When using large router bits, it is always advisable to make smaller initial passes of the wood before making the final cut, this way you ease your way into the wood making safer cuts that are easier on the router and the router bit and often result in better cuts.
Smaller bits can often be used at the highest router speed, especially the very smallest bits ... BUT, there are exceptions.
Smaller bits are often used in edging and depending on many variables, like species or wood, bit speed, cut of the wood, the moisture content of wood, sharpness of router bit and even construction of router bit ... you may encounter wood burning. When this happens you may need to speed up or even slow down the speed of the router, and sometimes it just doesn't make any difference what you do ... the wood burns.
Rule of thumb ... Larger bits slower .... smaller bits faster and adjust as needed.
Copyright Colin Knecht
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