About this item Square Hole Drill Bit Set: come with 1 square hole bit adapter and 5 square hole drill bits, Drill bits diameters: 1/ 4 Inch (6.4mm), 5/ 16 Inch (8mm), 7/16 Inch (11mm), 1/ 2 Inch (12.7mm), 5/8 Inch(16mm), and hand drill clamp diameters ranging from 38 to 55 mm/ 1.5 to 2.2 inches for easy installation and use; Please note that it is only suitable for bench drill and hand drill with clamps Quality Materials: the square hole drill bit adapter is made of quality carbon steel, strong and durable, can firmly fix the wood, the drill bit adapter measures about 6.3 inches/ 16 cm in length, upper inner diameter is about 0.75 inch/ 1.9 cm, lower diameter is about 2.17 inches/ 5.5 cm, reduce the use of error, specially designed with mortise bit accessories drill bit will not be blocked by wood chips, high hardness, no rolling, cutting speed, the bit is sharp, please take it out safely Efficient and Accurate: the bit adapter and the matching drill attachments in 5 sizes make it easier to use, and the precision design of the drill press mortise attachment ensures that you can drill the right mortise and mortise holes in the fastest way; More convenient and faster than mortise machine Widely Applicable: combines 1 square hole drill bit adapter with 5 square hole drill bits; This layout simplifies the process of drilling square holes in wooden planks; With this accessible and straightforward tool, you can reduce your efforts, catering to both beginners and workers; Appropriate for construction, carpentry DIY, decoration industry, which is suitable for compression board, plastic, density board, sandalwood, pine, ash, pine and other materials with low hardness Dual Support Bracket: square hole drill bits for wood are reliable and useful, suitable for bench drill and hand drill; Square hole bit adapters are ideal for woodworking, furniture manufacturing and other related industries › See more product details