One of the most notable current trends in deep hole machining (DHM) is multi-tasking. 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 to the same format.
The reason for this industry trend emanates from the oil and gas, and aerospace industries, where many high value components require deep hole machining, such as valve blocks and landing gear parts. Traditionally, manufacturing these components demands the use of dedicated machines, but the call for consolidated operations means a single ‘multi-task’ platform offers significant benefits to end-users.
Deep hole machining with Sandvik Coromant
Deep hole machining is the preferred method for drilling hole depths up to 150 x the hole diameter. This can be done in different machine set-ups. The most common method is rotating the work piece while the tool is fed in a linear movement. Rotating tool is another option as well as a combination of the two.
Regardless of method, the basic principles of drilling still apply, and the correct choice of cutting speeds and feeds are crucial. Satisfactory chip breaking, and removing the chips from the cutting edge without damaging the tool or work piece, is essential. One of the most important success factors is an effective coolant system.
Deep hole machining is carried out using three different machining systems: Single Tube System (STS), Ejector System or by applying gun drills.
Single Tube System suitable for:
- In materials with poor chip forming properties such as stainless steel, and low-carbon steel.
- In materials with an uneven structure when chip breaking problems exist.
- More advantageous for long series production.
- When large diameter holes are required.
- Requires dedicated deep hole drilling machine.
Ejector system suitable for:
- Requires no seal between the workpiece and the drill bushing.
- Adapts to existing machines, preferable in conventional lathes, turning centres, machining centres and horizontal boring machines.
- For machining workpieces where sealing problems can occur.
- An advantage when it is possible to use a predrilled hole instead of a drill bushing for guidance, for example in machining centres
Gun drill
- For small diameters.
- Can easily be applied to machining centres by using a pre-drilled hole for guidance.
- Requires high coolant pressure.
Guhring – Single fluted deep hole gun drills
In the machining world, drilling depths of 10xD and deeper are regarded as deep hole drilling operations, whereby smaller drilling depths can naturally also be produced with gun drills. Advantage is taken of the positive side effects, as for example good surface quality, low deviation from concentricity and optimized alignment accuracy. Tailor-made precision as well as exstock gun drills offer high cutting accuracy, alignment accuracy and surface quality even for extreme drilling depths. At Guhring, single-fluted gun drills for example are designed specifically according to the circumstances of each cutting task. Their speciality: On rigid machines Guhring gun drills prove to be especially flexible, powerful and effective. Guhring solutions even make deep hole drilling possible in high-alloyed steel and extreme types of chilled cast iron. Or if we take the solid carbide EB 100 gun drill which is capable of, to a certain extent, extreme cutting parameters with equally high process safety.
High pressure cooling – has become a matter of course
In recent years, internal cooling has established itself for all drilling tools. Coolants are now living up to their name and being supplied via coolant ducts to where they are urgently required. Considerable improvements in tool life and less breakages have been achieved by this measure for twist drills, taps etc.
Every conventional machine tool currently on the market can be supplied with high pressure internal cooling and is therefore also suitable for deep hole drilling. The share of gun drills on machining centres, lathes etc. is forever gaining more importance. The process is therefore increasing in popularity in the machining world
EB 100 – Ratio length gun drills
EB 100 gun drills are a single flute tool designed to drill extra deep holes on conventional CNC machining centers without the need for specialized gun drill equipment. Drilling depths of over 75xD can be reached with Guhring‘s EB 100 CNC style gun drill. These precision deep hole drills have full solid carbide one-piece construction from the shank to the cutting edge using Guhring’s ultra-fine grain carbide. The nano-ATM coated point improves abrasion resistance at the cutting edge and increases the temperature at which these drills can effectively operate. The specialized point grind is a universal design that is well suited to the job shop environment. Solid carbide construction provides improved rigidity within the cut and precision hole size and location accuracies. EB 100 gun drills do not require peck cycles in most applications. They are best suited for hole depths that are beyond the reach of the RT 100 T twist drill. Pilot hole drilling is required before any application of the EB 100 style gun drill.
Reference:
www.sandvik.coromant.com
www.guhring.com