Wirtschaftlich Bohren mit Köpfchen

The TTD replaceable head drill is the primary application for the TTS (Torque Transfer System) interface. The interface owes its stability to the radially arranged Hirth serration with 12 or 18 teeth, depending on the diameter of the adapted solid-carbide drill head being used. Due to the serration’s form closure, variable geometries of the replaceable head are possible. In addition, optimal torque transfer and high radial run-out and change-over accuracy are ensured.

The replaceable drill head is secured by a threaded pin affixed to the side of the tool holder. This allows the drill bit to be changed directly in the machine. The positioning aid integrated in the serration ensures that the chip flutes and coolant transfer from the tool holder to the replaceable drill head match. With its cutting-edge geometry, the drill head has a quality and performance level similar to solid carbide drills.
 

‘The true advantage of these drills comes into play in hardened materials, which it can machine reliably’, Geßner reports. ‘We achieve a long tool life here, which reduces our throughput of drill bits.’ At Mangner, bores used to take place prior to hardening. By eliminating the need for an additional clamping step, set-up time has been reduced. This increases efficiency in manufacturing, thereby providing the company with added value.

The previously used tool system had a particular weak point: if a solid-carbide drill head broke off, the drill bit holder was usually also damaged. In Geßner’s experience, this has never happened with MAPAL. After breakage, work could always continue with a new drill head, limiting any resulting damage. ‘I primarily considered changing the tool system from a cost perspective’, says Mike Mangner, explaining why he chose MAPAL.
 

Mangner uses the drills above all to pilot deep bores as well as complete bores for cooling, so-called coolant boost. While the normal lead geometry of the cutting edge is 140°, MAPAL also offers variants for special applications. A 180° tip can execute countersink bores, for example, which would otherwise only be possible with a milling cutter. Ball-nose drills enable radii at the end. Geßner reports that if handled with care, the drill heads can be reground up to three times by MAPAL. ‘This is very sustainable and lowers the average price per tool.’

The tool package delivered by MAPAL includes diameters from 12 to 45 mm, whereby the tool lengths are 3xD, 5xD, 8xD and 12xD. ‘We cover a certain diameter range with replacement head drills in increments of tenths’, Geßner specifies. ‘The tools would be unaffordable with drills made entirely of solid carbide.’ The many sizes reflect the various requirements of manufacturing. Series of up to 100 parts are rare here. Typical lot sizes are between one and 10 pieces. The material is often heat-resistant 1.2343 steel, but special materials, steel with varying degrees of hardness and aluminium are also processed.