Rated 5 out of 5Â by 1
Rated 5 out of 5Â by BigDoug An excellent tool for following a pattern or edge
I needed to make a number of pieces with an accurate hole about 3.15" in diameter, not a size that was available in a large hole saw, so I devised a plan to route the circle in the blank, using a normal plunge router to make a circular groove almost all the way into the wood.
Key to the process was using an accurate pivot pin with a tight fit in the router base AND the wood blank.
The groove was started with a plunge bit, rotating the workpiece around a center point. The plunge bit was not used to complete the full depth of the circular groove, because it would have lost the center pivot if the full circle loosened the small circle cut from the larger piece.
I made the groove in three passes, each a bit deeper than the previous. The third pass was done when the plunge bit was still in the router. I pushed the bit all the way through the blank, but only rotated it partially around the circle at full depth. That left the center disk connected by a layer of wood, and supported by about 2/3 of the circumference of the groove. At this point, I inverted the blank, so the groove was on top. I changed to the flush trimming router bit at this time,
I used THIS bit with a guide bearing to route the rest of the 3" diameter circular groove in a thick piece of popular or baltic birch. The guide bearing followed the smooth edge of the groove that had been made by the straight plunge bit.
The resulting hole was clean and accurate. Both of the bits seem to be very sharp and did not burn the wood, after about 8 of the calibrated holes were completed.
July 22, 2014