The starrett oooooooops Arbor

Now you can fix such vexations. Simply screw the hole saw for the existing hole onto the “OOPS” arbor (it accepts both 1/2" and 5/8" threaded cutters), screw the correct hole saw onto the pin-lock arbor, then place the "OOPS" arbor in the pilot drill hole. For the system to work, the inside and outside hole saws must have a size difference of at least 3/16". Perfect when installing new door lock hardware, or when enlarging holes for new piping in an old house. (Hole saw blades not included). Made in USA.

The No. A19 is another new arbor called the "Oops". It is actually a pilot drill adapter/arbor that fits in place of the drill in Nos. A1, A2 or A10 regular hole saw arbors. It works like this:

If, for instance, you drill a hole with a 1" (25 mm) saw when you intended to use a 2" (50 mm) saw, the first thing you do is say "oops" to yourself while telling your wife that you drilled the small hole first so you could check for accuracy.

The second thing you would do, is to put a 2" (50 mm) saw on a No. A2 or No. A10 arbor. Then take the pilot drill out of that arbor.

Next, take the "Oops" arbor and put the 1" (25 mm) saw on it and insert the 1/4" (6.3 mm) shank of that arbor in the drill hole of the No. A2 or No. A10 arbor. The 1" (25 mm) saw will now pilot everything while the 2" (50 mm) saw cuts the proper hole and your wife realizes she married well! Arbor also comes in handy in an old house when you need to increase pipe opening holes.