I had considered the issue of using an auger bit for counterboringing a hole. The method that occurred to me was to place a pilot over the screw point to guide the bit in the center of the original hole.
I have tried using auger bits with damaged or less than stellar threads on the screw point. I found that they tend to stop cutting a few turns after the spurs have bottomed out and the radial cutting edges engage.
While randomly surfing the web tonight I find that once again what I thought was a new idea had been thought of before.
At the bottom of the page is a catalog listing for “Old Tools of course”.
Near the upper right side of page are Auger Bit Guides.
At the bottom of the catalog page under the heading “An Old Fellow” the writer suggests that the Irwin Style bit is an idea that had been thought of before also.
As he says “There is nothing new under the sun.”
aka Old Sneelock