## 3 Experimental Work  
The experimental work mainly focused on the comparison between the Cut-list and the conventional system when both were tested at four different machining settings (2 cutting speeds and 2 feed rates). Because the new system has more settings capability compared to any conventional system, Cut-list was initially evaluated at 3 impinging angles in the feed direction, 3 impinging angles against feed direction and 3 stand-off/impinging distances, giving 27 tests at each setting of cutting speed and feed rate. Only the best trial (setting of impinging angles positions in feed and against feed direction and stand-off/impinging distance that gave best responses in terms of lowest Ra, etc.) of each of the 27 tests was used for the comparison with the conventional system. On the other hand, the conventional system was only tested in four different tests (cutting speed and feed rate were investigated at two levels each: 95, 200 m/min and 0.1, 0.15 mm/rev respectively. Nozzle elevation angle (\(\alpha\)) was 40\({}^{\circ}\) for all trials. Experiments were performed on a CNC Cincinnati 750-Sabri vertical machining centre (Cincinnati Machine UK Ltd., Birmingham, UK, 1997) with a maximum spindle speed of 8000 rpm and an 11 kW drive motor. Step shoulder-down milling experiments were carried out on annealed Ti-6 Al-4V ASTM B 265 grade 5 samples in the form of a 103 \(\times\) 25 \(\times\) 11 mm block. Each trial involved a cutting length of 103 mm and a new cutting insert was used. Coarse grain uncoated carbide milling inserts were used. Sandvik H13A (R390-11 T3 08M-KM) inserts were mounted on an \(\mathcal{O}\)18.5 mm \(\times\) 110 mm long square shoulder milling tool holder with an overhang distance of 60 mm to eliminate chatter. A single tooth cutter (Sandvik Coromant, Halesowen, UK) was used to avoid the influence of tool run-out on tool wear measurements. The inserts had a nose radius of 0.8 mm, 90\({}^{\circ}\) lead angle, and positive rake angle. A water-miscible cutting fluid (Vasco1000, Jemtech Ltd., East Sussex, UK) containing 45% pure vegetable oil (950 kg/m\({}^{3}\) mass density and 53.2 cP @ 40 \({}^{\circ}\)C dynamic viscosity) was used. The fresh cutting fluid was blended at the 10% concentration ratio and was regularly checked using a hand-held refractometer (Cromwell Tools, Luton, UK). The thermal and physical properties of the blended VO-based fluid were; 988 Kg/m\({}^{3}\) mass density, 1.8 cP at 25 \({}^{\circ}\)C dynamic viscosity, and 3.97 J/g\({}^{\circ}\)C average heat capacity. Average surface roughness (Ra) of the machined samples was measured using a Taylor Hobson Surtroni 3+ (Taylor Hobson UK, Leicester, UK). All Ra measurements were conducted in accordance with ISO 4287 and ISO 4288 using a 0.8-mm cut-off and an evaluation length of 4 mm. An Alicona Infinite Focus G4 optical scanner (Alicona UK Ltd., Kent, UK) was also utilised to capture the average tool flank wear (VB). Average tool flank wear (VB) was measured following each trial and after cutting a 110-mm length of the titanium workpiece in accordance with the standard ISO 8688-2 (1989). Each cutting tool was used only for one test to avoid accumulation of wear from different tests. Top burr heights were measured using the digital micro-depth gauge and measurement location is shown in Figure 4. Cutting force signals were collected using a piezo-electric dynamometer (Kistler 9257A, Kistler, Winterthur, Switzerland) which was mounted under the workpiece jig and then connected to charge amplifiers, with the output signals analysed using Kistler Dynamware software (Type 2825A-02, Kistler, Winterthur, Switzerland, 2014). Workpiece temperature was measured using mineral insulated Long Sheath Plain Pot 2 mt PFA (T-type) thermocouple sensors (TEMPCON, West Sussex, UK, 2016).