Effects of machining parameters when reaming aluminium±silicon SAE 322) alloy A.A. Bezerra a ,A.R.Machado a,* ,A.M.SouzaJr. b ,E.O.Ezugwu c a DEEME, Federal University of Uberla Ãndia, Uberla Ãndia, MG, CEP 38400-089, Brazil b Fiat Automo Âveis S/A, Betim, MG, CEP 32501-970, Brazil c Machining Research Centre, School of Engineering Systems and Design, South Bank University, London SE1 0AA, UK Received1October1999;receivedinrevisedform6October2000;accepted6February2001 Abstract Thispaperevaluatesthedimensionalstabilitydiameter,roundnessandcylindricity)andsurfaceroughnessofreamedcylindricalholes usingK10cementedcarbideweldedbladereamersonaluminium±siliconhypoeutecticSAE322)castalloyatvariouscuttingconditionsin ordertooptimisethecuttingprocess.Thefollowingparameterswereindividuallyvaried:depthofcut,cuttingspeed,feedrate,helixangle, numberofblades,marginsizeandrakeface®nishingofreamers.Powerconsumptionduringthereamingoperationwasalsorecorded.The testresultsshowthatsatisfactoryholequalitycanbeachievedduringreamingbyemployingsmallerdepthsofcut,lowercuttingspeeds, higherfeedratesaswellasstraight-¯utereamerswithmanyblades[ExperimentalMethodsforEngineers,3rdEdition,McGraw-Hill,New York,1978]andsmallmargins.Reamingathigherfeedconditionsimprovestheaccuracyofholesproducedattheexpenseofanincreasein power consumption and deterioration in the surface ®nish generated. The use of reamers with many blades can improve the accuracy, surface ®nish and roundness of holes produced at the cost of poor cylindricity and higher power consumption during machining. # 2001ElsevierScienceB.V.Allrightsreserved. Keywords: Reaming; Aluminium±silicon alloy; Cutting conditions; Helix angle; Surface ®nish; Dimensional stability 1. Introduction Modern machining requirements often demand mass productionofholeswithgoodsurface®nishandgeometrical accuracywhichareneededforprecisionassembly[1].These requirementsarenotoftenmetbyusingconventionaltwist drillssincetheyhavetoful®lseveraltasks:thecuttingedges have to generate two identical chips, the chips have to be conveyedbythehelical¯utesoutofthehole,thenecessary forcesandtorqueshavetobetransmittedbythebodyofthe drill,thetoolhastobeguided®rstbythetipofthedrilland laterbythemarginsontheouterdiameter,theheatgenerated hastobedissipatedpartlybythedrillbody.Thesecomplex demands are partly in contradiction to each other. On one hand, the ¯utes should be as wide as possible to provide suf®cient space for conveying the chips, and, on the other hand, the shaft or body of the drill must have enough strength and adequate rigidity to transmit the torques and trustforceswithoutbreakageandwithminimumdeforma- tionandvibration[2].Inpractice,theholesarecreatedwith twistdrillsandreamingisperformedasasecondaryopera- tionwhereasingletoolcanbeusedtoreamalargenumber of holes. Reaming can be performed with any kind of machine tool that has rotating shank thereby eliminating, inmanycases,theuseofprecisionoperationslikegrinding, honing or burnishing [3]. The reaming process has large application in the auto- motive industry which has recently witnessed a signi®cant development in vehicle technology, using light materials such as aluminium±silicon alloy in engine head blocks. Determination of correct machining parameters to ensure production of good quality holes in this alloy is usually dif®cult due to the softness of aluminium alloys and, to a lesser extent, the presence of hard particles which tend to weld onto the tool face resulting in built-up edge BUE) formationandassociatedproductionof``erratic''chipsand poor surface ®nish. These promote overheating and pre- maturefailureofthecuttingtool[4].Additionofsiliconto aluminiumalloysimprovestheircastabilityattheexpenseof higher abrasion resistance which accelerates tool wear. Thisworkinvestigatestheeffectsofdepthofcut,cutting speed,feedrate,helixangle,numberofblades,marginsize andrakeface®nishingofcementedcarbidereamersonthe JournalofMaterialsProcessingTechnology1122001)185±198 * Correspondingauthor.Tel.: 55-34-239-4148;fax: 55-34-239-4206. E-mail address: alissonm@ufu.br A.R. Machado). 0924-0136/01/$ ± see front matter # 2001ElsevierScienceB.V.Allrightsreserved. PII:S0924-013601)00561-1