How to use a hole saw to make a large hole larger.

[The machine]

I recently replaced my xmd3 with a cmd6 on my 2005 270 SD. The remote control for the old system had a smaller hole for mounting on the helm than the new remote needed. The old hole was about 2" diameter, and the new unit needed a 3" diameter hole. Obviously you cannot use the 1/4 inch drill pilot that you would normaly use on a hole saw, since there is already a 2" inch hole where you want to put the larger hole. My solution was to take a piece of 3/8 plywood scrap and cut it to a size where I could fit it behind the panel I wanted to work on. I then caught two of the mounting holes for this panel with the piece of plywood and held the plywood through those holes with wood screws, that were smaller than the mounting screws, that hold the panel on. I now had a solid piece with no hole that I could drill the 1/4 pilot through and which would now guide the hole saw. This method allows you to keep the hole center line in the same spot as the old hole or move it. I hope this is a helpfull tip to somebody.

 

[src]

Another method: Take a scrap board and drill a number of holes in it the same size as the original hole (2"). Take the plugs that you have drilled out, and stack them on the center bit of your 3" hole saw until they protrude beyond the cutting blade (glue/screw as needed to make them stack). You now have a "guide" on the drill that fits into the original hole, allowing you to drill the larger hole without letting it wander.

 

[highball]

I can fit 2 hole saws on same arbour. This mean I would have the 3 inch hole saw as normally installed but I would add or screew the 2" so it rests at bottom of 3". the 2" is the guide for the 3"