Figure 70. The exaggerated hole errors caused by an incorrect drill point geometry and the manufacturing techniques for its subsequent correction . Drilling and Associated Technologies  Figure 71. Reaming can correct an assymetrically drilled hole – when correctly adjusted.  Chapter  large harmonic variation in the ‘plots’ is depicted, as is the case when a ‘Floating reamer’ with roller drive has been used inappropriately. Floating Reaming Solid machine reamers can be ‘oated-down’ 59 a pre- drilled hole, to produce a much straighter reamed hole, than would otherwise be the case. When ‘oat- ing’ reamers within their specially-located toolhold- ers, two techniques are used to ‘oat reamers’ (i.e see Fig. 72), these are: 1. Radial play – where the machine reamer has lim- ited movement laterally with respect to the princi- pal axis, 2. Composed radial and pendulum play – this has both radial play, together with a degree of limited angular movement (i.e. this motion is similar to that of a Grandfather clock’s timing mechanism, via its pendulum motion). NB  is latter ‘oating’ technique has the potential for a combination of both radial and pendulum motions to the machine reamer. ese unrestrained kinematic motions gives it free motion without lateral and angu- lar constraint, to simply follow the ‘line of least resis- tance’ along the spindle axis, as the reamer progres- sively feeds down through the predrilled workpiece. .. Radially-Adjustable Machine Reamers Special-purpose machine drill/reamers (Fig. 74a) are oen utilised in high-volume production envi- ronments such as in the automotive sector, for util- ity engines which can account for >55,000 complex- reaming operations per week. Conversely, for defence vehicle engines the production volumes are quite low, accounting for <300 operations per month. Typical operations on such automotive components, using a machining centre include the reaming of: 59 ‘Floated-reaming’ , relates to the reamer’s ability to have some degree of lateral compliance, namely limited motion, allowing it some ‘play’ to follow the hole’s path, but still correcting for any previous ‘helical wandering’ by the drill. • Cylinder head tappet rail drill-reaming – in a sin- gle operation, • Cylinder head valve seats and guides – machining both features, in the parent bore and nish machin- ing, Figure 72. Solid machine reamers can be ‘oated-down’ a pre-drilled hole, by two distinct ‘oating techniques’: (I) radial play, (II) composed radial pendulum play. [Courtesy of Guhring Ltd.] . Drilling and Associated Technologies  • Engine block and crank bores and cheek faces – nish machining, with this latter feature requiring controlled ‘radial infeed’ of the cutting/reaming in- sert. NB  e special-purpose ‘radial-infeed’ tooling neces- sary for the satisfactory machining of the cheek faces of this latter low-volume production engine block, will now be briey discussed. Case-Study of Engine Block Bore Features In this novel, but interesting automotive ‘case-study’ , all of the challenges facing such special-purpose reamers are present. Here, the machining application consisted of the following: a six-cylinder diesel cast iron engine block for an armoured personnel car- rier, reaming at 70 m min –1 , requiring a bore straight- ness of 0.02 mm/m, tolerance on the bore diameter of 0.025 mm, with >0.003 mm tolerance between the individual journals. e solution to this demanding industrial problem, was the machining with two tools and three operations of the crank bore and the genera- tion of two cheek faces – this latter operation was nec- essary to minimise the tted cranksha’s end oat. is particular special-purpose reamer had a ra- dial feed-out/retract cutting insert requirement for the nal-machining of the cheek faces. erefore, the base-tool holder contained a thrust and feed-out mechanism, in addition to the whole tooling assem- bly ‘running-true’ , so that it could be ‘datum-out’ and precisely and axially-set with respect to its potential engine block machining features. e radial mecha- nism would incorporate an actuator sha mechanism which can be pulled-/pushed-back, thereby resulting in either a radial infeed, or retraction, respectively, of the cutting insert. is bi-directional control of the feed-out/-in of the radial mechanism is achieved in conjunction with the CNC feed spindle of the machin- ing centre. In general, these special purpose reamers, have two guide pads and a blade (Fig. 74a) with the reaming blade set with a back-taper, producing the well-known characteristic ‘saw-toothed prole’ to the reamed sur- face (Fig. 74b – right). Such reamed surface texture to- pography has been highly magnied in the schematic diagram (Fig. 74b – right) and, requires very high vertical magnication of the surface topography (i.e. x50,000) to see any trace prole details at all! e posi- tion of the cemented carbide guide pads, with respect to the blade is critical to the reamer’s performance, as is the residual stiness of the whole cantilevered tool- ing assembly. For many automotive industrial reaming applica- tions, the components are oen cast from high-silicon aluminium materials, as the addition of the element silicon, creates a micro-grained and harder cast struc- ture, than would otherwise be the case. However, the disadvantage from a machining viewpoint, is that the resultant cast matrix is highly abrasive to the cutting edge. Under these circumstances, the reamer’s blade Figure 73. Reamers in action, reaming automotive parts. [Courtesy of Shefcut Tool & Eng’g Ltd.] .  Chapter  Figure 74. High-performance reamers, having the ability for radial infeed (i.e. ‘feed-out inserts’) – when tted. [Courtesy of Cogs- dill Tool & Eng’g Ltd.] . Drilling and Associated Technologies  is oen produced from an abrasive-resistant mate- rial such as PCD, in order to maintain and extend the tool’s life and holding a good cutting edge over many machined parts. .. Reaming – Problems and Their Remedies For any resultant reamed surface, its form, accuracy and surface quality are tremendously improved by dividing the machining process into either, roughing, or nishing reaming operations. Low cutting speed together with high feedrates, in association with good lubrication agents oering adequate cooling poten- tial, provide the basis for optimum reaming practice. While, observing these ‘rules’ , improves both the reamed surface quality and its individual tolerance. It is worth restating, that a reamer only follows the pre- drilled hole, consequently it cannot correct for any previous alignment errors that might be present (i.e. see the schematic diagram in Fig. 70). Although er- rors between the spindle’s axis and the axis of the pre- drilled hole, can be adjusted with the aid of ‘oating reamer’ toolholders (Fig. 72). In Table 6, the following fault-nding chart may be useful in tracing the pos- sible causes of some common reaming problems. 3.4 Other Hole-Modification Processes Once the hole has either been: cast, core-drilled, or drilled into solid workpiece material, it oen requires a further post hole-making operation to complete the job, for example, a tapping operation. ere are a num- ber of these pre- and post-drilling hole operations that require specic tooling to nish o the hole-making activities. e most popular of these are briey men- tioned below, but this is by no means an exhaustive account of the many oen hybrid operations that are available to the potential designer, or machinist. Countersinks ere are several reasons why a countersink tool might be employed when machining features on a compo- nent, ranging from: •   Countersinking  a  countersunk-headed  screw  – for ‘ush-tting’ to the surface (Fig. 75a), •   Short  tapers – can be adequately machined on a component, •   Providing a lead – for a soon-to-be-tapped hole, •   Deburring  operation – on a previously drilled hole. Countersinks are available with a range of included taper angles and come in a variety of dimensional sizes, the most popular being either: 60°, 90°, or 120°, or indeed ‘specials’ can be ground to suit any angular and diametral workpiece features, of varying lengths. Countersinks are available from simply HSS, through to a coated cemented carbide matrix. Counter-Boring Counter-bored tooling (Fig. 75b) is available as either a solid tool, or is designed to be modular in construc- tion. is latter modular counter-boring tooling, oers a range of exibility to machine a wide assortment of component features, by simply changing the ‘pilot‘, or cutting element’s diameter. e ‘pilot’ as its name im- plies, follows a pre-drilled hole and guides the counter- bored cutting element enabling it to remain concentric with the hole’s axis. is is important for any cap-head bolts that require to be recessed either ush to a part’s surface, or sunk below its outer face. Counter-boring is also employed to machined a clearance face in the female part feature allowing for a stepped bar to have a ush face to locate against, or simply to provide clear- ance for such a workpiece feature. Again, as with most of these tool materials, they are produced from HSS, through to coated cemented carbides. Spot-Facing Spot-facing tooling is normally utilised to produce a consistent and uniform seating on for example, a cast, or forged component, allowing a washer, or bolt-head to be ush across its contact face. Spot-faced tools (Fig. 75c), are available as either a solid, or modu- lar constructional design – the latter version, giving greater exibility across a wider range of features to that of the former counterparts. Materials for these tools are similar to those mentioned for other post- drilling tooling, namely, HSS through to coated ce- mented carbides.  Chapter  Table 6: Potential reaming problems and their possible causes, with some remedies Reaming problem: Possible causes and some remedies: Holes to large i) Concentricity error of either: machine spindle, toolholder, or tool. (ii) Damaged t between tool and toolholder (i.e. taper, chuck, or collet). (iii) Bevel lead on tooling incorrect. (iv) Cutting speed, or feedrate too high. (v) If problem is the result of workpiece material, eliminate it by using a weaker coolant medium (i.e. by increasing its cooling potential, sacricing some of the lubricating abilities). Hole too small i) Tool tolerance incorrect. (ii) Ductile material that contracts after reaming – possibly eliminated by using a quick spiral reamer. (iii) Excessive heating during the reaming process: perhaps by the hole expanding, then subsequently contracting. (iv) Reamer blunt. (v) Cutting speed, or feedrate too low. (vi) Insucient stock left on for reaming: tool seizes in the hole. (vii) In most cases, eliminate problems using a more concentrated soluble oil mixture (e.g. 1:15 to 1:10, alternatively use cutting oil). Conical, non-circular and other hole malfunctions (i) Machine spindle not concentric. (ii) Bevel lead not correct. (iii) Axis of pre-drilled hole and reamer not in alignment – eliminate by using a ‘oating’ toolholder. Unsatisfactory surface texture of hole i) Reamer blunt. (ii) BUE on edges, caused by ‘cold welding’ , eliminate by using high concentration coolant, possibly cut - ting oil, or by a reduction in reamer’s land width – to almost zero. (iii) Cutting speed too high, feedrate too low. (iv) Stock removal allowance too small – caused by the pre-drilled hole being too large. (v) Incorrect bevel length. Reamer seizes and breaks (i) Reamer blunt. (ii) Too high a cutting data employed (i.e. speed and/or feed). (iii) Pre-drilled hole too small. (iv) Poor coolant mixture – lubrication too dilute. (vii) Reamer geometry requires modication. [Courtesy of Guhring Ltd] . Drilling and Associated Technologies  Figure 75. Some alternative hole modication machining tooling. [Courtesy of Guhring Ltd.].  Chapter  Back Spot-Facing Back Spot-faced tools (Fig. 75d), are usually employed in ush-facing an internal hole’s face on either a cast- ing, forging, or wrought stock. e Back Spot-facing operation, enables a bolt-head, or nut and its washer to be accurately seated. In some instances, it is possible to generate, the back-face, rather than to form it, via specially-modied tools that are fed to the other side of the part, then circular interpolation techniques are used to create the required back-face. NB  With most of these post-drilling operations, the cutting data is restricted and calculated to the outer di- ametral dimension of the part feature to be machined. Solid post-drilling tooling can usually be operated at higher cutting data to that of their modular tooling counterparts. References Journal and Conference Papers Agapiou, J.S. and DeVries, M.F. On the Determination of ermal Phenomena during Drilling – Part I. Analytical Models of Twist Drill Temperature Distributions. Int. J. Mach. Tools Manufact., Vol. 30 (2), 203–215, 1990. Agapiou, J.S. and DeVries, M.F. On the Determination of ermal Phenomena during Drilling – Part II. Compari- son of Experimental and Analytical Twist Drill Tempera- ture Distributions. Int. J. Mach. Tools Manufact., Vol. 30 (2), 217–226, 1990. Anderson, P. Good points [Drilling geometries]. Cutting Tool Eng’g, Vol. 45 (6), 50–56, 1993. Astakhov, V. Gundrilling Know-how. Cutting Tool Eng’g, 34–38, Dec. 2001. Atabey, F. Lazoglu, I. and Alintas, Y. Mechanics of Boring Processes – Part I. Int. J. Mach. Tools and Manufact., 463–476, Vol. 43, 2003. Atabey, F. Lazoglu, I. and Alintas, Y. Mechanics of Boring Processes – Part II – Multi-insert Boring Heads. Int. J. Mach. Tools and Manufact., 477–484, Vol. 43, 2003. Benedict, B.W. and Lukens, W.P. An Investigation of Twist Drills; Part 1. Bull. Univ. o Illinois Eng’g Exp. Station, No. 103, 1917. Boston, O.W. and Gilbert, W.W. e Torque and rust of Small Drills Operating in Various Metals. Trans. of ASME, Vol. 58 (2), 1936. Griths B.J and Grieve, R.J. e Role of the Burnishing Pad in the Mechanics of Deep Drilling Processes. Int. J. Prod. Res., Vol. 23 (4), 195–205, 1985. Colvin, K. Farewell to BUE [In drilling]. Cutting Tool Eng’g, 44–47, Feb. 2001. Comstock, T.R. Chatter Suppression by Controlled Mechani- cal Impedence. PhD esis, Dept. of Mech. Eng’g, Univ. of Cincinnati (Ohio), USA, June 1968. Deren, M. Check the Index. Cutting Tool Eng’g, 51–55, Sept. 2002. Fiesselmann, F. and Dietz, G. Pointing Towards Drilling Rates. Modern Machine Shop, 1–7, June 1982. Fitzgerald, G.W. A Comparative Study of the Lanchester Damper and the Segmented Slug Damper in Boring Bar Applications. Proc. of ASME, No. 81–DET–90. Frade, T. Twist Drill Shape-up. Cutting Tool Eng’g, Vol. 42 (2), 39–44, Feb. 1990. Galloway, D.F. Some Experiemnts on the Inuence of Vari- ous Factors on Drill Performance. Trans. of ASME, 191– 231, Feb., 1957. Habeck, A. Steadying the [Boring] Bar. Cutting Tool Eng’g, 46–50, Dec. 2000. Haggerty, W.A. Eect of Point Geometry and Dimensional Symmetry on Drill Performance. Int. J. Mach. Tool Des. Res., Vol. 1, 41–58, 1961. Hall, J. Boring Tools get … Interesting. Cutting Tool Eng’g, 34–37, Dec. 2004. Hanson, S. Cutting the Hard Stu Right. Manuf. Eng’g., 179–187, May 2005. Inada, S. et al. On a Method to Prevent Chatter in Boring Operations. Bull. of the JSME, Vol. 17 (108), 835–840, June 1974. Inamura, T. and Stat, T. Stability Analysis of Cutting under Varying Spindle Speed. J. of JSPE, Vol. 43 (1), 80–85, 1977. Javed, M.A, Littlefair, G. and Smith, G.T. Tool Wear Moni- toring for Turning Centres. Proc. of LAMDAMAP Int. Conf., Computational Mechanics Pub., 251–259, 1995. Johnson, B. Reaming Technology. Industrial Tooling Int. Conf., Southampton (UK), Molyneux Press, 132–152, Sept. 2001. Johnson, B. Reaming Application for the Automotive Indus- try. Industrial Tooling Int. Conf., Southampton (UK), Test Valley Pub., 288–304, Sept. 2003. Kahng, C.H. and Ham, I. Eect of Metallurgical Properties on Drill Life. In: Inuence of Metallurgy on Hole Mak- ing Operations, ASM Pub. (Ohio), 182–204, 1978. Kashara, N., Sato, H. and Fani, Y. Phase Characteristics of Self-excited Chatter in Cutting. J for Eng’g for Ind., ASME Pub., Vol. 114, 393–399, Nov. 1992. Drilling and Associated Technologies  Klein, R.R. and Nachtigal, C.L. A eoretical Basis for Ac- tive Control of Boring Bar Operations. Trans. of ASME: J. Dynamic Systems Measurement and Control, Vol. 97, June 1975. Larsson, C. Optimizing Deep-hole Drilling. Cutting Tool Eng’g, 32–38, Feb. 1998. Lewis, B. Turn your Wipers on. Cutting Tool Eng’g, 47–51, Jan. 2003. Matsubara, T., Yamamoto, H. and Mizumoto, H. Chatter Suppression by using Piezoelectric Active Damper. Dept. of Mech. Eng’g, Report, Tottori Univ. (Japan), 79–83, 1987. McColl, M. and Leadbetter, R. CAD of Multifacet Drills. Proc. of 13 th NARMRC (SME), 490–495, 1984. New, R.W. and Au, Y.H.J. Chatter-proof Overhung Bor- ing Bars Stability Criteria and Design Procedure for a New Type of Damped Boring Bar. Proc. of ASME, No. 79–WA/DE–3. Ng, K.W. and New, R.W. Prole Boring Operations – Tests on Damped Bars using Known Vibratory Forces, Trans. of Int. J. Prod. Res., Vol 14 (2), 149–169, 1976. Noaker, P.M. Drilling with a Twist, Manufact. Eng’g., 47– 51, Jan. 1990. Oxford Jr., C.J. On the Drilling of Metals: 1 – Basic Mechan- ics of the Process. Trans. of ASME, Feb. 1955. Oxford Jr., C.J. Fundamentals of Drilling, Tapping and Reaming. In: Inuence of Metallurgy in Hole-making Operations, ASM Pub., 1–18, 1978. Patterson, H. Strictly Boring. Cutting Tool Eng’g, 22–30, Vol. 47 (7), 1995. Ramakrishna Rao, P.K. and Shunmugam, M.S. Accuracy and Surface Finish in BTA Drilling. Int. J. Prod. Res., Vol. 25 (1), 31–44, 1987. Rivin, E.I. A Chatter-resistant Cantilever Boring Bar. Int. Conf. Wayne State Univ. 403–407, Oct. 1986. Skuma, K. Taguchi, K. and Katsuki, A. Study on Deep-hole Boring by BTA System Solid Boring Tool – Behaviour of Tool and Its Eects on Prole of Machined Hole. Bull. Ja- pan Soc. Prec. Eng’g. Vol. 14 (3), 143–148, Sept. 1980. Salama, A.s. and Elsawy, A.H. e Dynamic Geometry of a Twist Drill Point. Int. Conf. AMPT’93, Dublin City Univ. Pub., Vol. 1, 41–50, Aug. 1993. Schlesinger, G. e Cutting Angle of Twist Drills. e Engr., Vol. 166 (4), 138, Dec. 1938. Scott, N. Balanced Boring. Cutting Tool Eng’g, 62–66, April 1993. Shaw, M.C. and Oxford Jr., C.J. On the Drilling of Metals: 2 – the Torque and rust in Drilling. Trans. of ASME, Vol. 79, 139–148, June 1957. Simpson, G., Krenzer, U. and Gsänger D. Capacity of Drill- ing Tools with Indexable Inserts, Industrial Tooling Int. Conf., Southampton (UK), Shirley Press, 33–43, Sept. 1997. Smith, G.T. Investigating the Machining Performance of Damped and Undamped Boring Bars. Proc. of LAM- DAMAP Int. Conf., Computational Mechanics Pub., 509–523, 1997. Stoddard, B.C. e Replacements [Replaceable drill points]. Cutting Tool Eng’g., 34–39, Jan. 2007. Takemura, T., Kitamura, T. and Hoshi, T. Active Suppression of Chatter by Programmed Variation of Spindle Load. J. of JSPE, Vol. 41 (5), 489–498, 1975. Trigger, K.J. and Chao, B.T. An Analytical Evaluation of Metal Cutting Temperatures. Trans. of ASME, Vol. 73, 57, 1951. Trmal, G.J. and Wyatt, J.E. Model for Predicting the Torque and rust and its Application in Monitoring Drilling Operations. Industrial Tooling Int. Conf., Southampton (UK), Molyneux Press, 201–210, Sept. 2001. Valikhani, M. and Chandrashekhar, S. An Experimental Investigation into the Comparison of the Performance Characteristic of TiN and ZrN Coatings on Split Point Drills using the Static and Stochastic Models of the Force System as a Signature. Int. J. Adv. Manuf. Tech., Vol. 2 (1), 75–106, 1987. Watson, A.R. Drilling Model for Cutting Lip and Chisel Edge and Comparison of Experimental and Predicted Results – 4; Drilling Tests to Determine the Chisel Edge Contribu- tion to Torque and rust. Int. J. Mach. Tool Des. Res., Vol. 25 (4), 393–404, 1985. Webb, P.M. Dynamics of the Twist Drilling Process. Int. J. Prod. Res. Vol. 31 (4), 823–828, 1993. Webb, P.M. e ree-dimensional Problem of Twist Drill- ing. Int. J. Prod. Res. Vol. 31 (5), 1247–1254, 1993. Williams, R.A and Gibson, A.V. A Survey of Fundamental Aspects of the Drilling Process. Tech. Paper 19, Proc. of CSIRO (Melbourne), 1964. Wilshire, B. Getting Peak Performance from Indexable Drills. Cutting Tool Eng’g, 30–40, Feb. 1999. Witte, L. Cutting Forces in Drilling Operations: Part One. Modern Twist Drilling Tech. Vol. 2 (3) 8–11, 1982. Witte, L. Cutting Forces in Drilling Operations: Part Two. Modern Twist Drilling Tech. Vol. 2 (3) 12–15, 1982. Books, Booklets and Guides A Guide to Surface Texture Parameters. Taylor Hobson Pre- cision Booklet No. 800–305 4K CP1299 (English). Boothroyd, G. and Knight, W.A. Fundamentals of Metal Machining and Machine Tools. Marcel Dekker (NY), 1989. Boring with Tuned Bars, Sandvik Booklet No. HV-5300:008 ENG, 1983.  Chapter  . Vol. 166 (4), 138, Dec. 1938. Scott, N. Balanced Boring. Cutting Tool Eng’g, 62 66 , April 1993. Shaw, M.C. and Oxford Jr., C.J. On the Drilling of Metals: 2 – the Torque and rust in Drilling. . I. and Alintas, Y. Mechanics of Boring Processes – Part I. Int. J. Mach. Tools and Manufact., 463 –4 76, Vol. 43, 2003. Atabey, F. Lazoglu, I. and Alintas, Y. Mechanics of Boring Processes – Part. Tools Manufact., Vol. 30 (2), 217–2 26, 1990. Anderson, P. Good points [Drilling geometries]. Cutting Tool Eng’g, Vol. 45 (6) , 50– 56, 1993. Astakhov, V. Gundrilling Know-how. Cutting Tool Eng’g,