Today my curiosity started getting the best of me concerning Russell Jennings auger bits and their designations.
One of the places I looked for a clue was an old Adel's 4 volume set for the carpenter.
The information to fulfill my quest was not found, but there was an illustration of brass plugs for use on auger bits when a small hole had to be drilled to a larger size. For example, a 1" hole needing to be enlarged would have the brass plug of 1" size screwed onto the lead screw of the larger bit and then provide a guide for the larger bit.
Maybe a wooden dowel could be used in this way and a hole can be bored with your largest auger to match the dowel and then follow up with the expansion bit.
jim
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)