Disston Screwdiggers fulfil the same function as Screwsinks but the countersinking part can be slid up & down the drill part of the tool. Ideal for drilling, countersinking & counterboring in one operation. This means that a No. 8 Screwdigger can be adjusted to predrill for different lengths of No. 8 Screw. Uses 7 / 64in Drill Bit. To ensure an acurate fit we suggest you use the same Plug Cutter from the Disston br&. For No 8 screw.