ORIGINAL ARTICLE Influence of hole diameter, workpiece thickness, and tool surface condition on machinability of CFRP composites in orbital drilling: a case of workpiece rotation Nazir Ahmad 1 & Sarmad Ali Khan 2 & Syed Farhan Raza 2 Received: 22 November 2018 /Accepted: 8 April 2019 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract Carbon fiber-reinforced polymer (CFRP) composites are considered as difficult-to-machine materials. Due to good strength to weight ratio and comparatively light weight than metallic alloys, their usage in aerospace industry is increasing where drilling is primary machining process for joining of components. Material removal using drilling process in CFRP composites is challeng- ing due to its abrasive nature together with certain problems such as matrix burn out and uncut fibers etc. The advantages associated with orbital drilling over conventional drilling technique are now established. Literature review in orbital drilling of CFRP composites revealed that published data is limited to geometrical and analytical modeling while loading a cutting tool in rotation as well as in orbital motion. In the current work, orbital drilling (OD) is performed by rotating the workpiece in an orbit instead of cutting tool. Cutting tool is used for spindle speed only. Thickness of the workpiece and tool surface condition was studied at two levels, i.e., 6 mm and 8 mm when employing coated and uncoated cutting tools. Holes of three different diameters of 8, 10, and 12 mm were drilled. Tool wear, workpiece surface roughness, and diametric error were reduced due to less loading on the cutting tool. Performance of coated tool was found to be better than its uncoated counterparts on all output responses. Keywords Orbital drilling . CFRP composites . Tool wear . Surface roughness . Diametric error 1 Introduction Till now, aeroplane components are connected via rivets where bores of high quality are required before joining and drilling is the primary machining process for such kind of bores. The use of composites is increasing in aeronautical and aerospace industries due to excellent properties such as high strength to weight ratio, relative light weight compared to metallic alloys and corresponding less fuel consumption [1, 2]. Specific problems involving cracks, thermal degra- dation of matrix and delamination often arise while drilling composites. As a result of these problems, mechanical prop- erties are degraded and lead to rejection of machined com- ponents made up of composite. The choice of proper drilling methods and operating conditions are necessary for com- posite parts production. Compare to conventional drilling, orbital drilling (OD) has several advantages. With this pro- cess, different borehole geometries can be drilled using one tool with material being removed in axial and radial direc- tion. This is achieved by rotation of the cutting tool on its own axis and about another eccentric principle axis while feeding the tool through the material. Broadly, this process has certain key characteristics on the basis of which it can be differentiated from conventional drilling, i.e., tool diameter is less than the bore diameter, intermittent contact of tool edges with the hole surface, small chips formation, and low thrust force. Better space provision between tool and hole surface allows effectual chip evacuation. Additionally, bet- ter heat dissipation eliminates the risk of matrix burnout together with less chip induction damage. Intermittent cut- ting provides sufficient cooling hence eliminate the need of cutting fluid; therefore, this process is considered as clean process Moreover, burr-/delamination-free machining is possible with orbital drilling [3, 4]. A review of the avail- able literature is presented for context building the context and highlighting the gap. * Syed Farhan Raza sf.raza.rezvi@gmail.com 1 Department of Mechanical Engineering, The University of Lahore, Lahore, Pakistan 2 Department of Industrial and Manufacturing Engineering, University of Engineering and Technology, Lahore, Pakistan The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-03713-2