Description Disston Screwdiggers fulfil the same function as Screwsinks but the countersinking part can be slid up and down the drill part of the tool. Ideal for drilling, countersinking and counterboring in one operation. This means that a No.6 Screwdigger can be adjusted to predrill for different lengths of No. 6 Screw. Uses 3/32in Drill Bit. To ensure an accurate fit we suggest you use the same Plug Cutter from the Disston brand. For no 6 screw