The hollow-stem auger cutter head should be the same size as the hollow-stem augers to drill and convey cuttings effectively.

• A. Smaller than
• B. It depends on drilling conditions
• C. Larger than
• D. The same size as

Answer: (D)

When hollow-stem drilling, the cutter head must fit the hollow stem so that cuttings are cut and immediately captured to be carried up by the auger flights. Matching diameters creates a continuous cutting surface that aligns with the conveyance path inside the stem, ensuring efficient lifting of cuttings to the surface. If the cutter head is smaller, cuttings can slip past the cutting edge and accumulate in the space around the head, reducing lifting efficiency and increasing the chance of clogging. If the cutter head is larger, it won’t fit through the stem properly and can bind or stall the drill, risking equipment damage. So, using the same size as the hollow-stem auger ensures effective drilling and reliable removal of cuttings.