PURPOSE: To prevent damage of a honing stone and deterioration of grinding accuracy of works by conducting exact, rapid and simplified selection of whether they will be ground as they are expected before they are supplied to a stack honing device.

CONSTITUTION: A supplying shooter 1 is supported on the device 4 so as to make a circular work W fall naturally from the upper inlet 2 toward the lower outlet 3. At the right and left near the inlet are equipped a fluid cylinder 6 and an auxiliary fluid cylinder 7 face to face. The fluid cylinder measures and controls the internal diameter which moves forward and backward at right angles to the work guiding way of the shooter 1. At the front end of a measuring bar 8 is formed a guiding part 13 so that the bar 8 can be easily fitted to the internal circumference of the work W. The auxiliary measuring bar 17 is fixed to the piston level 18 of the cylinder 7. In this way, whether the work is good or not is selected rapidly and exactly and damage of grinding wheels and deterioration of processing quality are prevented before they happen.