Modified DLC-Coated Guide Pads for BTA Deep Hole Drilling Tools

Abstract

The BTA (Boring and Trepanning Association) deep hole drilling process is commonly used to machine boreholes with a large drilling depth-to-diameter ratio (l/D) and outstanding workpiece quality. The asymmetric tool design leads to a nonzero radial component of the cutting force and the passive force, which are conducted to the borehole wall by so-called guide pads. These guide pads smooth the borehole wall by a forming process and improve the surface quality. Processes, that machine materials with a high adhesion tendency, such as high alloy stainless steel, suffer from poor surface quality in the borehole and the adhesion from the workpiece material on the guide pads. In this paper modified Diamond-Like-Carbon (DLC) coated guide pads for BTA deep hole drilling tools are investigated. The scope of the experiments was the reduction of the adhesion by reducing the friction coefficient of the guide pads, as well as the improvement of the quality of the borehole wall.

Lateral Vibrations in Deep Hole Drilling Due to Land Width Variation

“…Different studies showed, that it is possible to adjust the damping of the drilling process by adjusting the land width [22][23][24]. Previous investigations have insufficiently dealt with the influence of the land width on the vibration of twist drills.…”

“…It can be deduced that damping in form of friction at the main cutting edges as a result of wear does not lead to avoid lateral vibrations. Biermann et al [23,24] investigated the damping during Boring and Trepanning Association (BTA) drilling, in which the authors varied the geometry of the guide pads on the tool, including the coating. The results led to a reduction in abrasive wear and to improve the surface of the bore wall.…”

Investigation into deep hole drilling of austenitic steel with advanced tool solutions

“…During the machining process, high mechanical loads stress the guide pads, which lead to an extensive wear of these components [3]. Depending on the materials to be machined, such as austenitic steels, these loads increase and exceed the initial state multiple [4]. These steel grades in particular cause high abrasive and adhesive tool wear [5].…”

“…These steel grades in particular cause high abrasive and adhesive tool wear [5]. Previous research at the Institute of Machining Technology has already focused on the wear of guide pads in single tube system (STS) deep hole drilling of austenitic steels [4,6]. Special attention was paid to the shape of diamond-like carbon (DLC)-coated guide pads, on tool wear behaviour and on quality of the drilled bore holes.…”

“…They found out that a friction reducing coating (e.g. ta-C) is appropriate to reduce abrasive wear effects [4,6]. In order to evaluate the guide pad's characteristics and estimate the cutting performance, the analysis of microstructures and mechanical properties was performed [12].…”