Cutting Tool Technology Episode 4 docx

4 Milling Cutters and Associated Technologies ‘Mit der Dummheit kämpfen Götter selbst vergebens.’ TRANSLATION: ‘Against stupidity the Gods themselves struggle in vain. ’    (1759 – 1805) [Die Jungfrau von Orleans, III.vi] 4.1 Milling – an Introduction At its most basic level, a milling operation involves a co-ordinated linear, or multiple-axis feeding motion of the multi-edged cutter 1 as it rotates across and into the workpiece. Milling cutters are usually tted into a driven rotating machine spindle for a range of machine tools. e type of machines available is quite diverse and include: milling machines, machining centres 2 , mill/turn centres 3 , plano-mills 4 , etc. In special cases, 1 ‘Fly-cut milling’ , is the exception here, as it is considered a milling operation that will normally utilise only one cutting edge, it is similar in design and operation to that of a two-cut- ting edged trepanning tool. A ‘y-cutter’ is usually employed for the machining of large diameter circular features, where either the hole is the required component feature, or the cir- cular blank is the necessary item from for example, a large wrought plate/sheet. 2 ‘Machining centres’ , are milling machines equipped with an automatic tool changer – for fast and ecient ‘tool changing’ (i.e. to reduce down-time to a minimum), having either a vertical, or horizontal spindle conguration, although multi- spindle machines can also be used. Predominantly, machining centres have what is known as: ‘orthogonal axes’ – having each axis at 90° in relation to each other. A ‘basic’ machining centre has three orthogonal axes (i.e. X, Y and Z), but can have rota- tional axis (i.e. A, B and C) incorporated onto them, or built into the structure of the machine tool. Some of these machine tools, may have 6-axes (i.e. 3 linear and 3 rotational), or more, necessary for any complex free-form sculptured machining work. 3 ‘Mill/turn centres’ , as their name implies, can turn parts and, with controlled rotational axes, coupled with driven/live spin- dles, they can accurately and eciently generate: prismatic features, faces, splines, keyways, cams, etc., onto the work- piece at one setting – termed ‘One-hit machining’. In order to increase the versatility of such machine tools, these mill/turn centres can also be tted with ‘co-axial spindles’ , where two spindles are coincident with each other (i.e. their respective spindle centrelines are in-line, but opposing each other), al- lowing for example, twin tool turrets to work simultaneously on two parts. ese machined components may have quite distinctly dierent part geometries/dimensions and, this level of complex and sophisticated costly plant, requires quite sig- nicant linear and rotational CNC axes programming capa- bilities. is type of conguration of mill/turn centres with co-axial spindles, oer two machines in one, but on a quite small shop-oor ‘footprint’ – an important and perhaps vital benet when oor-space is at a premium. 4 ‘Plano-mills’ , have the ability to generate large at surfaces with their traditional range of single-point planning tools, but with an additional milling capability of having one, or more milling machine spindles tted, for large-part surface milling operations to be conducted on the large part. milling operations can be utilised for multi-axis free- form ‘sculpturing’ of complex-curved workpieces, us- ing equipment such as 5-, or 6-axis machining centres, or even robots with ‘slaved’ (i.e. tted) spindles, all these machines being equipped with specially-ground milling cutters – necessary for ‘double-curvature’ ma- chining operations. A milling cutter’s design and its respective cutting edges come in a vast range of shapes and sizes (i.e. see Fig. 76). Each of the individual ‘mills’ cutting edges – as the cutter rotates and is fed into the workpiece, will mill a certain amount of material from the part. Milling operations are an ecient way of re- moving either excess stock from previously fabricated parts, or by machining from wrought material. e production of a milled surface, oers a machined sur- face texture that is consistently good, having accurate and repeatable dimensions, oering great exibility in terms of the geometric types and shapes for these milled components. A milling operation is an ‘intermittent cutting ac- tion’ , where each individual cutting insert continu- ously enters and exit’s the cut, unlike turning, which is basically a continuous machining operation, once the cut has been engaged. It follows that with each cutting tooth impacting onto the work’s surface (‘intermittent cutting’), its operation will be aected by: the cutter’s inherent robustness, the machine tool’s condition and the spindle power availability. ese factors will have a great inuence on the cutter’s ability to eciently ma- chine the desired component features. Milling opera- tions can vary considerably and can be performed by a wide variety of machine tool congurations, with a diverse range of tooling (Fig. 76) and across a large ar- ray of workpiece materials, shapes and geometries. At an early point once the engineering drawing(s) have been designed and produced and, prior to ma- chining the part, an in-depth study of the type of cuts to be made to produce the desired component features, either out of: wrought, cast, forged, or extruded mate- rials should be instigated. Oen at this initial stage in machining assessment, the ‘study’ should address new approaches to machine the desired part geometries, by attempting to manufacture the part in the shortest possible cycle-time 5 . Moreover, when considering the 5 Cycle-times for the manufacture of parts, should include the productive operations (i.e. all machining times) and non- productive elements (i.e. including: tooling and workpiece set-ups, tool-changing operations and any necessary form of workpiece measurement), in producing the overall completed component.  Chapter  individual part feature to be machined, judge whether just one cut, or several passes are the best machining strategy for its subsequent production. In scheduling 6 particular components for milling operations, the se- lection of which CNC type of machine tool congu- ration should be of prime importance, for example a milling machine, or machining centre equipped with either a: vertical, or horizontal spindle, or a univer- sal mill, or even a large gantry mill. Once the CNC machine tool has been selected, other secondary, but perhaps nonetheless important factors should be ad- dressed, such as the potential accuracy and repeatabil- 6 Scheduling of parts, is based upon a range of crucial produc- tion decisions. Typically the nal decision may be due to a number of interrelated factors: when the parts are needed, the quantity of parts in the batch, their geometry and size, the availability of the correct machine tool, any potential cycle-time reductions when utilising a specic machine tool. Other important machining economic factors may need to be addressed such as: workholding methods, cutting tool moni- toring, automated part loading/unloading, etc. In many large- scale volume production environments, ‘line-balance’ deci- sions that may have to be made could arise. Particularly when a diverse sequence of operations on component features that must be machined, these being part of a series of operations across several machine tools. ity of the production process including the attainable milled surface texture, together with rigidity/instabil- ity of the overall process for the selected machine. is latter factor of milling stability, via the rigidity of the machine-tool-workpiece loop, will dictate not only the anticipated milling cutter’s tool life, but aects the to- tal performance of the overall production process with large-scale ramications for potential component part economics. .. Basic Milling Operations Regardless of the type of milling cutter selected, a ma- chining operation utilises one, or more of the follow- ing production milling techniques, with any variations in methods being related to feed directions in relation to the tool’s rotational axis. e three basic milling op- erations are: • Face milling (Fig. 77a, b and c – depicts some typi- cal machined features produced by facemilling). A facemilling operation is a combined cutting ac- tion by the inserts, in the main on the tool’s periph- ery and, to a lesser extent by insert edges on the cutter’s face. In facemilling, the cutter rotates at 90° to that of the direction of radial feed against the workpiece. Facemilling has a D OC in an axial direc- Figure 76. Just a small selection of the vast range of milling cutters avail- able for both machining and mill/turn centres. [Courtesy of Seco Tools] . Milling Cutters and Associated Technologies  tion, which is determined by how deep the periph- eral cutting insert’s edges cut, with the insert’s faces on the edge of the cutter generating the nished workpiece surface. • Peripheral milling – radial (Fig. 78) – utilises pe- ripherally-located cutting edges that are situated in a milling cutter body which is horizontally spindle- mounted. e cutter rotates around a horizontal axis, this axis being parallel to the tangential feed- ing direction. Peripheral milling has a D OC in a radial direction that will determine how deep the cutter’s diameter will penetrate into the workpiece. ere are two peripheral milling strategies that can be used with these horizontally-mounted cutters, Figure 77. Just a few of the ma- chined features that can be produced by a range of face milling cutters. [Courtesy of Sandvik Coromant] .  Chapter  these are either ‘Up-cut’ (Fig. 78 top-right denoted ‘U’), or ‘Down-cut’ (Fig. 78 top-le denoted ‘D’) 7 milling operations – more will be said on this topic shortly. • Peripheral milling – tangential (Fig. 79) – allows the cutter to not only face mill, but has the capabil- ity to work along a third direction feed – axially (i.e. downward into the part’s surface – Fig. 79 – top). Essentially, this milling operation is a form of drill- ing, being performed by the cutting edges on the cutter’s face, oen termed ‘slot-drilling’ 8 . is tech- nique allows the cutter – perhaps ground with radi- used indexable cutting inserts (i.e. see Fig. 79b), to machine open and closed pockets, or slots, enabling the cutter’s peripheral edges to complete a range of cutter-paths to open up the a rectangular, or irregu- lar ‘pocketed features’ 9 in the workpiece (Fig. 79a). Up-Cut and Down-Cut Milling Here (Fig. 78), the workpiece is fed into the horizon- tal-mounted peripheral milling cutter, which has its rotation either clockwise (i.e. termed ‘down-cut mill- 7 ‘Up-cut’ and ‘Down-cut milling’ , these two peripheral milling techniques are sometimes referred to as either: ‘Conventional milling’ , or ‘Climb-milling’ operations, respectively. 8 ‘Slot-drilling’ , normally utilises two cutting edges on the cutter’s face. One cutting edge being longer that the other – crossing the cutter’s centreline, thus as it rotates, its dissimi- lar length of cutting edges will sweep across the total area of cut. is action, allows the cutter to be plunged-down into the workpiece’s surface and then feed along – to produce a slot – hence the name: ‘slot-drill’. NB If the slot-drill has its cutting edges rounded (i.e. radiused), a ‘Ball-nosed slot-drill’ will result, and such a cutter geometry can produce a range of ‘blended/curved’ workpiece features, allowing complex-curved proles (i.e ‘sculpture-milling’) op- erations to be undertaken. In some cases, the curvature of the radius is modied (i.e. in the case of an ‘APT tool’ – meaning: automated-programmed tool) geometry is ground, to mini- mise step-over/cusp height eects, when (post) nishing-o operations are more speedily rendered on complex-curved workpiece features. For example, when completing the high- quality nishing operations on moulds and dies. 9 ‘Pocketed features’ (Fig. 79a), these operations can be gener- ated by feeding the cutter to a pre-determined series of suc- cessive depths these being consecutively opened-up by a range of tool-path strategies. Typical of the techniques for such pocketing cutter path control, is to employ either ‘Lace-’ , or ‘Non-lace cuts’ – more will be said on this later. Figure 78. Peripheral milling (radial), can be undertaken by either: up- or down-cut milling operations NB These dierent milling cutter rotational directions, impart totally dissimilar resultant force vectors whilst machining, play- ing a signicant role in the attendant: power consumption fac- tors, resultant machined workpiece residual stresses and sur- face inegrity present, together with geometric shapes/types of workpieces that can be succesfully machined. [Courtesy of Sandvik Coromant] . Milling Cutters and Associated Technologies  ing’ – Fig. 78 top-le ‘D’), or anti-clockwise (‘up-cut milling’ Fig. 78 top-right ‘U’). Hence, the workpiece is fed either with, or against the milling cutter’s rotation direction, which determines the nature of the begin- ning, or completion of the cut. In ‘down-cut milling’ (Fig. 78 top-le), it can be seen that the workpiece direction of feed is the same as that of the cutter’s rotation, in the vicinity of the cut. In such circumstances of peripheral milling concern- ing the milled chip’s area, the chip thickness begins to decrease from the initiation of the cut, eectively reaching zero on completion of the insert’s peripheral rotation, prior to the adjacent cutting insert continu- ing this trend in chip development. Furthermore, as each milling cutter insert enters the cut with a large chip thickness, this avoids any potential rubbing and Figure 79. Axial feed milling using either: solid carbide end mills, slot drills, or a ball-nosed milling cutter NB These type of milling cutters can be widely utilised across a vast range op po- tential workpiece geometrically-shaped features. [Courtesy of Sandvik Coromant] .  Chapter  the likelihood of workpiece surface burnishing, mini- mising both the probability of temperature increases and work-hardening tendencies. As a cautionary note, although this is a very eective and ecient way of peripheral cutting, if any ‘back-lash’ 10 is present, then the cutter will attempt to ‘snatch’ , or at worst, ‘ride- over’ the workpiece’s surface, as it is pulled-into the cut. is possible ‘snatching-eect’ , being created by the resultant cutting force tending toward a back-ward direction (Fig. 78 middle-le). is adverse action, re- sulting from presence of ‘back-lash’ could even cause cutter, or spindle damage, together with part scrap- page, if it is not minimised/eliminated. In ‘Up-cut milling’ (Fig. 78 top-right), the work- piece feed direction opposes that of the milling cutter rotation, within the cutting vicinity. erefore, the chip thickness commences at zero and increases as it ap- proaches the exit point, at the end of the cut. Due to the fact that at the initiation of the cutting sequence the cutting edge has no eective forces acting on it, so it must be forced into the cut and during this time, some eects of rubbing/burnishing create excessive lo- calised friction, which in turn, results in an increased temperature. Here, contact with the workpiece mate- rial from the previous insert can work-harden the sur- face. Yet another disadvantage of utilising ‘Up-cut mill- ing’ , is that the resultant force (Fig. 78 middle-right) can attempt to li the workpiece on the machine tool’s table, therefore it must be securely clamped/xtured into place. e machine tool’s spindle power will depend on the either the feed force (V f ), or the resultant force 10 ‘Back-lash’ , is a problem concerning slideway ‘oat’ (i.e. slight, but unwanted lateral uncontrolled back-and-forward motion) in the machine tool’s leadscrew, or ballscrew. On conventional milling machines (i.e. with no CNC-controlled axes), these are normally equipped with an Acme thread (i.e. having a truncated Vee-form thread of 29° included angle), they require a ‘Back-lash eliminator’ to be tted, which when rotated/tightened on the split-nut assembly surrounding the Acme thread which is mechanically-connected to the work- piece’s table, reduces any back-lash present – thereby allowing down-cut milling to be successfully performed. NB Ballscrews, are usually tted to CNC-controlled machine tools, as they can be pre-loaded by the machine tool builder, thus minimising any potential back-lash problems. It is nor- mally desirable to use down-cut milling techniques in CNC machining, as it is more ecient cutting technique, in com- parison to that of up-cut milling. component, the relationship of these ‘Up- and Down- cut milling’ factors being schematically illustrated in Fig. 78 – bottom diagrams. is resultant force is a combination of the tangential and radial cutting forces. e resultant cutting force will dier signicantly in its vectored angle, depending upon the cutter position relative to that of the workpiece’s. ese vectored angles (Fig. 78 – bottom diagrams), will become larger with increased D OC – for ‘Up-cut milling’ , the net eect be- ing that the milling process needs more spindle power. In ‘Down-cut milling’ , due to the fact that the resultant force is in the same direction to that of the feed, it will signicantly reduce the feed power requirement. Yet another advantage of using a ‘Down-cut milling’ strat- egy, is that there will be no reverse change of direction, so any workpiece clamping is simplied. .. Milling Cutter Geometry – Insert Axial and Radial Rake Angles With any machining operation, the combination of the rake and clearance angles determines the cutting edge’s wedge angle, this greatly inuences the insert’s strength. Oen, cemented carbide cutting inserts have a small negative primary land present, this helps to avoid fracture during the intermittent cutting action associated with a milling operation. A helix angle is present on many milling cutters 11 , be it a: side-and- 11 Helix angles, can vary considerably, the helices being selected for the workpiece material to be cut. For example, when mill- ing aluminium, a quick helix is necessary to take advantage of the low shear characteristics of the material, conversely, when milling grey cast iron a slow helix is preferable, as this mate- rial is somewhat brittle in nature. In many instances when ma- chining the so-called ‘sticky’ materials such most aluminium grades, etc., then the milling cutter is designed to have a larger ‘chip-gusset’/‘chip-pocket’ (i.e. clearance space for the chip). is larger ‘chip-pocket’ may take the form of alternating the bias of the helices for the cutting edges on say, a peripheral milling cutter, having a positive helix on one tooth, with the adjacent tooth being of negative helix – typically a milling cutter of this design is the so-called: ‘staggered-toothed side- and-face cutter’. Milling Cutters and Associated Technologies  face cutter, face-mill, end mill 12 , slot-drill, etc. e helix angle brings the cutting edge progressively into cut, resulting in ‘quieter running’ , but instead of an orthogonal cutting action (i.e. with two component forces – tangential and radial – acting on the cutting edge), an oblique cutting action occurs (i.e having an additional axial force component present). is axial force component resulting from the geometry of the helix, has a tendency to either ‘pull’ the cutter out of the spindle, or push it towards it, depending upon whether it is of a le- or right-hand helix. For all of the designs for Endmills and Slotdrills currently available, there are basically three types of axial and rake angled cutting edge geometries, theses are: • Double-positive cutting edges (i.e shown in Fig. 80C) – normally employs a single-sided insert, as this geometry allows a relatively ‘free’ cutting/ shearing action. Here, the positive axial and rake geometries, produce low cutting forces, owing to the reduced chip thickness and a shorter length of contact at the chip/tool interface. As a result, less spindle power is necessary, enabling a lower insert strength requirement enabling high-shear cutting availability, when compared to either of the fol- lowing insert geometries. e manner in which the chip formation occurs is benecial, in that spi- ral chips are formed, which can easily be broken and exhausted from their respective chip pockets. When milling ductile materials such as grades of: aluminium, steel, as well as some stainless and heat- resistant steels, where there is a tendency to form BUE, the double-positive geometry is the only suc- cessful solution to machining such workpiece ma- terials. If the workpiece has a tendency to be some- what unstable, perhaps due to either its fragility, or 12 ‘Endmills’ , can not only have the cutting edges designed with a helix angle, but for the ‘solid’ end-milling varieties, they may have either their cutting edge land lengths interrupted by a groove this feature being a long-lead spiral groove – to act as a form of chip-breaker (i.e. they are oen called ‘Rippa-cut- ters’ – utilised for high stock removal rates), for long-chipping materials. For some cutter designs, such as: ‘Roller-, or Slab- mills’ , they can have cutting inserts staggered along the tool’s periphery covering the length of the body, to disrupt the long- chipping swarf (i.e. see Fig. 76). For Endmills versions of this inserted-toothed design, they are oen termed ‘Porcupine cutters’ (i.e. an example of a ball-nosed version, is depicted in Fig. 79b). clamping method, then the double-positive insert geometry is once again, the most suitable milling geometry to use. • Double-negative cutting edges (Fig. 80B – shown here with either a round insert – bottom-le, or square insert – top-right) – in this case, the radial and axial angles are both negative. When a double- negative insert is used, the required clearance is ob- tained by tilting the insert. is ‘tilt’ of the insert, has the added economical benet of allowing both sides of the insert to be utilised, enabling the avail- ability of more cutting edges coupled to stronger edges, when compared to the former insert geom- etry. is double-negative milling cutter insert ge- ometry, is most suitable for machining conditions involving heavy impact stresses, associated with workpieces produced from: hard steels, certain cast iron matrices and on some of their ‘chilled-sur- faces’ 13 , or ‘induction-hardened surfaces’ 14 – nor- mally using the ultra-hard PCBN-grades of inserts. With these ‘Double-negative’ insert cutting geom- etries, the demands on spindle power requirement and its stability are considerable, owing to the large cutting forces and chip thickness factors associated with this type of geometry. • Positive/negative cutting edges (Fig. 80A – illus- trating a square insert – top-le, or an inclined and chamfered square insert – middle-le). For ex- ample, in the case of Fig.79a (top-le), the insert 13 ‘Chilled cast iron surfaces’ , are used in order to produce a hard-wearing surface, this being necessary for example on the Vee-and-at slideways’ for cast lathe beds. Here, a ‘chill’ (i.e. normally a metallic interface) is for example strategically-po- sitioned in the cavity, prior to pouring the liquid melt. is ‘metallic chill’ acts as a ‘heat-sink’ to quickly allow solidica- tion at the liquid/wall interface, producing a high tempera- ture/cooling gradient and subsequent crystalline growth of small grains, that have become both locally hard and wear re- sistant, but are surrounded by a graphite-based matrix that of- fers excellent ‘damping’ qualities to the overall cast structure. 14 ‘Induction-hardened surfaces’ , are usually obtained by a trav- elling electric resistance induction heating/cooling unit. is equipment, once it has locally heated the surface, will be im- mediately quenched*, as the apparatus slowly moves along the required surface to be heat-treated, imparting a surface-hard- ened layer to the cast iron.*is induction-hardened surface now consists (i.e. metallurgically) of a very hard ‘white-iron’ , appearance – aer suitable metallographical preparation – with a white surface layer, once it has been suitably acid- etched.  Chapter  geometry comprises of a combined positive axial angle and a negative radial angle. Although the ba- sic form of the insert may have a negative geometry, the edge on its end face must be positive in order to give a positive axial rake. e spindle power require- ments for this combined geometry are a compromise between the lower demands of the double-positive insert geometry and the higher ones associated with that of its double-negative counterparts. With this positive/negative milling insert geometry, high feeds per tooth combined with large D OC ’s can be achieved, because the negative radial rake provides high insert strength, whilst the positive axial rake oers good chip formation, with the added bonus of directing the chips away from the cutter body 15 . For any general-purpose milling applications, the cutters having positive/negative cutting insert ge- ometries are usually ideal. 15 ‘Chip-evacuation/-exhaust’ , are terms that are readily used to explain how the chips are removed from the milling cutter’s body. It is a very important consideration, as any chip-jam- ming tendencies must be avoided at all cost, as the cutter, workpiece, or both, can be severely-damaged if this potential and avoidable problem arises. Figure 80. The rake and clearance angles for various types of face-milling cutter insert geometries. [Courtesy of Sandvik Coro- mant] . Milling Cutters and Associated Technologies  .. Milling Cutter – Approach Angles Although cutting insert axial and radial rake angles are important to correctly select, probably of similar importance is the milling cutter’s approach, or enter- ing angle (i.e described and illustrated in Fig. 81). e insert’s inclination can vary by pre-selecting the most suitable one for the workpiece to be milled. Of- ten a compromise has to be made when selecting the cutting insert’s inclination/approach angle. For ex- ample, inserts having an approach angle of 90°, are termed ‘Square-shoulder cutters’ (i.e. depicted in Fig. 83a – le), as their name implies, they are normally utilised when machining up to a shoulder, or perhaps a stepped-feature on the workpiece. ere are some problems associated with 90° approach angled milling cutters, their limitations are: • Chip thickness is at a maximum – for a given feedrate, resulting in high loads on the cutting in- serts, Figure 81. Face milling cutter insert approach angles. [Courtesy of Stellram].  Chapter  [...]... Des Res., Vol 22, 7–22, 1982 McNamara, D Getting Down [Plunge Milling] Cutting Tool Eng’g., 44 47 , Oct 2003 Richter, A The Right Angle [‘Angled’ Milling Heads] Cutting Tool Eng’g., 48 –53, July 20 04 Rowe, J Right Face [Face Milling] Cutting Tool Eng’g., 56–61, Sept 2001 Sandvik Coromant Geometries at Work [Milling Cutters] Cutting Tool Eng’g., 56–63, May 2003 179 Smith, G.T and Booth, S The Manufacture... Machinist, 43 45 , Dec 1996 Isakov, E Power Equations Cutting Tool Eng’g., 66–71, May 2001 Kennedy, B Facing Facts [Face Milling – Automotive Parts] Cutting Tool Eng’g., 29–37, Feb 2002 Kennedy, B Wall Smart [Thin-wall Milling] Cutting Tool Eng’g., 26–33, Feb 2007 Kline, W.A., DeVor, R.E and Lindberg, J.R The Prediction of Cutting Forces in End Milling with Application to Cornering Cuts Int J Mach Tool Des... in Machining Centres, Int Conf on Industrial Tooling, Shirley Press, 95–100, Sept 1997 Deren, M A Tale of Two Metals [Milling Stainless Steel] Cutting Tool Eng’g., 48 –56, May 2001 Deren, M Deep Impact [Milling Deep Pockets] Cutting Tool Eng’g., 40 45 , Oct 2001 Eacott, R Cutting Geometries for Milling and a New Approach to Chip Control Int Conf on Industrial Tooling, Molyneux Press, 52–61, Sept 1999 Ekback,... [Milling Cutter Applications] American Machinist, 51– 54, Nov 1996 Godden, T Tools for Multi-axis Machining Int Conf on Industrial Tooling, Test Valley Group, 255–266, Sept 2003 Heuwinkel, M and Richter, A Let’s Talk Radial [Approach Angles – Milling] Cutting Tool Eng’g., 64 70, May 2005 Heuwinkel, M As Easy as X, Y, Z [Helical Interpolation – Milling] Cutting Tool Eng’g., 58–62, Aug 2006 Isakov, E The Mathematics... Corp.] 176 Chapter 4 Figure 92.  A range of special tools (i.e customised), catering for specific company production needs [Courtesy of Ingersoll] Milling Cutters and Associated Technologies 4. 4 Customised Milling Cutter Tooling Custom-built tooling is as its name implies, offers quite considerably diverse tool designs (i.e see Fig 92 for just ‘snap-shot’ of a small range of these types of tools) Some of... Fig 84h the cutter has been moved just off-centre, causing a longer arc of cut for each insert, which is likely to reduce the tool s cutting life’ somewhat, but this is only part of the problem of off-centre cutting Returning to the cutter positioned centrally (i.e Fig 84g), here the direction of the radial component cutting forces will fluctuate, with respect to the cutting edges start and finish cutting, ... 307–316, 1993 Stabler, G.V The Fundamental Geometry of Cutting Tools, Proc IMechE, Vol/165, 14 26, 1951 Tlusty, J and Masood, Z Chipping and Breakage of Carbide Tools, ASME J of Eng’g for Ind., Vol 100, 40 3 41 2, Nov 1980 Yamane, Y and Narutaki, N The Effect of Atmosphere on Tool Failure in Face Milling – (1st Report) J Jap Soc Prec Eng’rs Vol 49 (8), 521–527, 1983 Books, Booklets and Guides Application... Chapter 4 Modern Metal Cutting – A Practical Handbook AB Sandvik Coromant Pub., 19 94 Oxley, P.L.B Mechanics of Machining Ellis Horwood Pub., 1989 Shaw, M.C Metal Cutting Principles Oxford Univ Press, 1989 Society of Manufacturing Eng’rs., Tool and Manufacturing Engineers Handbook – Vol 1 – Machining 4th Ed., SME Pub., Dearborn, Mich., 1983 Smith, G.T Advanced Machining – The Handbook of Cutting Technology, ... Machine Tools Marcel Dekkar (NY), 1989 Childs T.H.C., Maekawa, K Obikawa, T and Yamane, Y Metal Machining – Theory and Applications Arnold Pub., 2000 Ingersol Pub Fine Tuning [Milling Cutter Rigidity], 14 15, The Cutting Edge, No.3, 1987 Ingersol Pub Fine Tuning [Milling Optimisation], 14 15, The Cutting Edge, No.2, 1988 Ingersol Pub Fine Tuning [Milling Cutter Insert Density], 14 15, The Cutting Edge,... so-called ‘re -cutting effect’  24 that normally if present when utilising a large face-milling cutter In reality, the spindle camber is very slight and generally amounting 23 On many machining centres it is not always possible to tilt the spindle and, in such situations, back-, recutting is an unavoidable milling surface texture condition 24 ‘Re -cutting effect’ , this is the product of the cutting inserts . tool, any potential cycle-time reductions when utilising a specic machine tool. Other important machining economic factors may need to be addressed such as: workholding methods, cutting tool. of o-centre cutting. Returning to the cutter positioned centrally (i.e. Fig. 84g), here the direction of the radial component cutting forces will uctuate, with respect to the cutting edges. spindle and, in such situations, back-, recutting is an unavoid- able milling surface texture condition. 24 ‘Re -cutting eect’ , this is the product of the cutting inserts on the ‘back-edge’ of