Portable routers are used in woodworking to form edges and make shaped cuts.  Routers have a frame with a base section; the base section rests on the wood to provide a reference for the cutting tool.  A motor for rotating the cutting tool is provided inside of the frame. 
Routers have some type of adjustment mechanism to adjust the depth of cut.  This adjustment is typically done by moving the motor with respect to the frame.  As the motor is retracted from the base, the cutting tool is pulled back, reducing the depth of cut.  As the motor is advanced toward the base section, the cutting tool is also advanced, increasing the depth of cut. 
Routers may be provided with a cylindrical bushing around the cutting tool that is used as a guide for following a template during cutting operations.  To ensure accurate cutting with the guide bushing, the guide bushing must be aligned so as to be centered with respect to the cutting tool.  In the prior art, the bushing is centered by measurement; the distance between the bushing and the cutting edge of the cutting tool is measured and the bushing is centered accordingly.  This is a time consuming and inaccurate procedure, however. 
I have developed a novel press router, which is shown and described in U.S. Pat.  No.  4,652,191.  In the router of the '191 patent, a conical alignment fixture is used to center the bushing.  The alignment fixture has a rod and an integral conical portion.  To center the bushing, the rod is inserted through the bushing and is coupled to the motor by way of the collet.  Then, the motor is retracted into the frame to retract the conical portion.  The conical portion contacts the bushing, wherein the bushing is centered.  The bushing is then secured to the base. 
My patented router permits adjustment of the cutting depth without affecting the lateral position of the cutting tool shaft.  Thus, the guide bushing is centered by moving the motor with respect to the bushing.  In fact, the only way to center the bushing with the fixture of the '191 patent is to move the motor relative to the bushing, because the conical portion is integral to the shaft.  But, in some conventional routers, adjusting the cutting depth will affect the location of the cutting tool shaft relative to the bushing.  Thus, the bushing should be centered after the cutting depth is fixed.  But, with the fixture of the '191 patent, the conical portion is fixed to the shaft, so that the conical portion is unable to move into contact with the bushing once the cutting depth is fixed.  Thus, what is needed is a centering fixture that will center guide bushings on conventional routers.