What is a deep hole drill?

A deep hole is defined by its depth-to-diameter ratio (D:d), typically a hole greater than 10:1 is considered deep. Metal deep hole drilling has a wide range of applications across multiple industries, tracing its origins to the need for straighter, more precise gun barrels and expanding as other industries incorporated deep hole drilling processes to improve their own applications .

Deep hole drilling includes BTA drilling and deep hole drilling, as well as additional processes designed for specific tolerance targets, usually performed on BTA type deep hole drilling machines. Deep hole drilling is used in materials ranging from aluminum to superalloys, enabling tight diameter control, straightness and excellent surface finish on workpieces.

The process of deep hole drilling works by using special tools and setups to deliver high pressure coolant, cleanly evacuate chips and drill holes in metals to depths to diameters that cannot be achieved with ordinary CNC machines. This enables manufacturers to achieve their manufacturing tolerances and production requirements reliably, accurately and efficiently.

Deep hole drilling is usually performed on dedicated deep hole drilling machines, which are manufactured and assembled to optimize straightness and efficiency of the process. Advances in technology have enabled CNC machining centers equipped with high-pressure spindle coolant to perform gun drilling operations with limited depth-to-diameter ratios. UNISIG manufactures high performance BTA and gun drills for applications exceeding 400:1 D:d ratio.