Formulation and Characterisation of Eco-Friendly Cutting Fluids From Mahogany and Yellow Oleander Seed Oils

The continued use of mineral-oil-based cutting fluids in machining raises environmental, occupational, and disposal concerns, creating a need for renewable alternatives. This study formulated and characterised water-miscible cutting fluids from non-edible mahogany seed oil (MSO) and yellow oleander seed oil (YSO). The researchers extracted the oils by mechanical pressing, yielding 49% MSO and 62% YSO, respectively. Five MSO:YSO blend ratios (100:0, 75:25, 50:50, 25:75, and 0:100) were formulated with additives and evaluated using established American Standard for Testing of Materials (ASTM), Association of Official Analytical Chemists (AOAC), and American Oil Chemists’ Society (AOCS) procedures. Each test was conducted three times, and the arithmetic mean was reported. The extracted oils recorded kinematic viscosities of 42.21 and 38.68 mm²/s and flash points of 296°C and 288 °C for MSO and YSO, respectively. Multi-criteria evaluation identified the 50:50 blend as the optimum formulation, with pH 9.08, viscosity 1.97 mm²/s, specific gravity 0.9680, Grade 1 emulsion stability, 16% foam retention after 10 minutes, and Grade A corrosion protection. Preliminary turning of AISI 1018 steel with an uncoated HSS cutting tool at 569 rpm, 0.08 mm/rev feed, and 1.25 mm depth of cut yielded 33.7 °C cutting temperature, 0.08 mm tool wear and 1.578 µm surface roughness for the 50:50 blend, compared with 37.8 °C, 0.14 mm and 1.696 µm, respectively, for Rhenus TU 446. The findings demonstrate the technical feasibility of the optimum formulation and its potential as a renewable cutting fluid candidate for sustainable metalworking applications.