TOOL TIPS: Deep hole machining in ‘multi-task’ format

Many high value components, namely landing gear parts, require deep hole machining.

T-Max drill 424

T-Max drill 424

In the same way that it is possible to achieve common machining techniques such as milling, turning and gear cutting on a single machine tool platform, there is now growing demand to introduce deep hole machining (DHM) to the multi-task format.

This trend emanates primarily from the aerospace industry, where many high value components, namely landing gear parts, require deep hole machining. Traditionally, manufacturing these components demanded the use of dedicated machines, but the call for consolidated operations means a single ‘multi-task’ platform.

Principal among the advantages is quality. Enhanced concentricity between diameters will usually result from completing all operations on one machine. This arises from avoiding the need to transfer heavy components between machines. Productivity can also be enhanced due to saving set-up times. Furthermore, developing a multi-task platform that includes DHM creates a ‘green light’ process, where operators can press start and walk away safe in the knowledge a completed component will be the ultimate result. In large aerospace OEMs, these green light processes are essential to maximize machine utilization.

Tools of the trade

While these benefits are tangible, there are pre-requisites necessary to fuel the success of DHM in a multi-task format. For instance, the machine tool needs to exhibit suitable levels of torque, power and feed force to accommodate these demanding operations.

Sandvik Coromant is working on projects that demand multi-tasking with DHM, partnering with aerospace customers and machine tool vendors.

Holes up to 43 inches deep have been produced successfully deploying a multi-task format. While even deeper holes are possible, the demands on the machine climb in direct proportion. Enhanced torque, thrust and additional vibration controls are required. This becomes even more relevant when machining tough heat resistant super alloys and modified martensitic stainless steels typically found in modern energy and aerospace applications.

The coolant factor

Also, integrating DHM to a conventional machine tool requires an additional investment in a drill head, drill tubes, a rotary coolant adaptor and a new coolant tank. The existing tank with most machine tools will not be of sufficient capacity. For example, producing a two-inch-diameter hole will require in the region of 30-gallons-per-minute of coolant delivery for an ejector system and 60-gallons-per-minute for a single tube system (STS)—to aid both cooling and chip breaking/evacuation—hence a tank of around 300 to 600 gallon capacity.

Sandvik Coromant’s DHM technology developed for use on multi-task platforms is ejector-based. Although STS technology would offer greater coolant flow, the large investment in the pressure head makes for a financially unviable solution in a multi-task format. Using existing ejector-based solutions, deep holes ranging between 1-inch and 2.5-inch diameter can be achieved using a typical machining centre platform. Changing diameters can require swapping the head size and preparing the workpiece accordingly.

Self-contained ejector-based systems are essentially a drill tube comprising an inner and outer tube. Coolant is introduced at the spindle using a rotary connector, with the fluid passing between the two tubes. Ejector-based systems perform equally well on components featuring an irregular face, since the design of the rotary connector and drill head create a Venturi effect that draws coolant and chips through the inner tube.

Fit for purpose

The ejector system developed by Sandvik Coromant has been purpose-designed to allow deep hole drilling to be performed effectively on machining centers. To deal with the copious amount of coolant needed to ensure good chip evacuation Sandvik Coromant offers a connector with integral coolant supply housing. The coupling is incorporated into the rear of the connector that allows interchangeability among a wide range of basic holders.

Existing Sandvik Coromant ejector-based drilling and counterboring solutions include the ground drill head CoroDrill 808, CoroDrill 800.24 and several variants of T-Max drill 424 (pictured). And while these can be adapted to existing machines such as turning centers, universal machines and machining centers without major reconstruction, application support and advice is essential in generating optimized solutions.

Deep hole machining successes are founded on the continued development of processes and tools. Here, geometries and grades, along with efficient coolant and chip management, help achieve the required results at the highest penetration rates and machining security.

Courtesy of Sandvik Coromant.

About the Author
Canadian Metalworking / Canadian Fabricating & Welding

Lindsay Luminoso

Associate Editor

1154 Warden Avenue

Toronto, M1R 0A1 Canada

Lindsay Luminoso, associate editor, contributes to both Canadian Metalworking and Canadian Fabricating & Welding. She worked as an associate editor/web editor, at Canadian Metalworking from 2014-2016 and was most recently an associate editor at Design Engineering.

Luminoso has a bachelor of arts from Carleton University, a bachelor of education from Ottawa University, and a graduate certificate in book, magazine, and digital publishing from Centennial College.