Guide bushes are used as an alternative to a router bit with a bearing. Smaller bearings can seize, and therefore cause damage to the workpiece.
A router bit with a bearing is limited by the position of the bearing in relation to the height of the cutter and the required cut. A guide bush has a fixed position, with the router bit able to move up and down independent to the guide bush. Many commercially available jigs use a guide bush that runs against the jig.
The Base Plate Adaptor plate has a rebated 30mm hole, this allows the guide bush to be fitted so the guide only protrudes below the base of the router, to run against the template.
Many routers lack the ability to mount guide bushes, or only have a limited range of bushings available. The Carbatec CT-BPA-1 allows the fitment of the widely available 30mm threaded bushes used with Carbatec, Leigh, CMT and many other specialty jigs.
Note: Template Guide Bush shown not included.