Getting Started with Counter-Rotating Deep Hole Drilling
Typical machining centers are often not capable of deep holes greater than a 20:1 D:d ratio, and are not configured for counter-rotation. Rather, dedicated deep hole drilling machines are a superior consideration because they are designed specifically to manage accurate counter-rotation in gundrilling and BTA processes.
Deep hole drilling machines that enable successful counter-rotation include the right components, machined and assembled to maintain superior alignment. These range from the machine base, to rotating bearing groups and spindles, to tool and workpiece support – all of which uphold alignment and work as a system. This allows the machine to maintain accuracy while moving, and hold concentricity tolerances throughout the depth of the hole.
For deep hole machine builders, alignment considerations begin with the machine base. Each component is designed with alignment as a priority,as well as machining and environmental factors like temperature and gravity. Counter rotation may be possible on machines retrofitted with a second rotating group, but will often need to undergo an alignment improvement process which creates additional challenges. Equipment designed with this purpose will have the right combination of benefits to make concentricity tolerances manageable for nearly any operator.
On a counter-rotating drilling machine, a good operator interface will provide a full picture of process information, as well as allow control over process parameters, for fine-tuning and process repetition. Manufacturers can optimize their counter rotation application, and proceed into highly accurate and efficient production.
A general starting point for counter rotation is to allow one third of the total speed to come from the workpiece, and two thirds of the speed to come from the tool. This is a typically recommended starting point for counter-rotating drilling with confidence. Operators can adjust for their specific application, and work with industry partners for recommended parameters to meet deep hole drilling goals.
The addition of counter-rotation in a deep hole drilling process gives operators an additional factor to optimize for both specification and production requirements. The ability to hold improved concentricity tolerances with counter-rotation allows feeds to be run at optimal rates, as well as extends tool life. Manufacturers can reliably produce more parts per hour, with fewer tool changes and improved tool consumption.
For applications where concentricity is indeed critical, the productivity benefits are significant, and easily justify the added capability. Counter-rotation consistently produces a more concentric drilled hole, typically with higher surface cutting speeds, offering clear benefits to manufacturers in both accuracy and efficiency.
Manufacturers can increase capability, improve hole tolerances, and optimize productivity, ultimately cutting costs and providing a competitive manufacturing advantage. With the right resources, drilling deep holes with extreme concentricity is economical, repeatable, and commercially viable.