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TOOL WEAR, TOOL LIFE, HAND TOOLS AND MACHINE TOOLS

Email: 1 TOOL WEAR, TOOL LIFE, HAND TOOLS AND MACHINE TOOLSPROCESS OF CUTTING TOOL FAILUREC utting Tool Failure Plastic chipping due to mechanical breakage of the gradual wearA tool that no longer performs the desired function can be declared as failed Fig: e) Create wear & flank wearFig: (f) small & Larger Flank wear Typical wear pattern in cutting toolFLANK WEAR AND TIME RELATIONSHIPT hree stages o flank growth region (Break in region) state region (Temperature Insensitive region) failure (Temperature sensitive region)Flank wear formation depends on * Cutting Conditions (f, d, V, tool angles)* Properties of work material and tool materialFlank wear characterised by wear land (or Height) hfof wear band Fig: (a) Three stage flank wear curve, (b) Various elements of flank wear and crater wear, (c) Variation of various crater wear with time3 Temperature insensitiveareaTemperaturesensitive area12 Break in RegionTime (t) (min.)Flank Wear (mm), hfmmlCflfeTimehflfclfc(a)(b)(c)Tool wear Index, feed marks and surface finish Type of wear depends MAINLY on cutting speed Ifcuttingspeedincreases,predominantwearm aybe CRATER wearelse FLANK wear.

TOOL SPECIFICATION • Apart from tool material, one has to give tool angles and tool nose radius in the following sequence while going to purchase or asking some one to make a tool : • Tool specifications (all six angles, and nose radius) :7-8-5-6-9-4-1mm. • Back rake angle (70), • Side rake angle (80), • End clearance (relief) angle (50),

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Transcription of TOOL WEAR, TOOL LIFE, HAND TOOLS AND MACHINE TOOLS

1 Email: 1 TOOL WEAR, TOOL LIFE, HAND TOOLS AND MACHINE TOOLSPROCESS OF CUTTING TOOL FAILUREC utting Tool Failure Plastic chipping due to mechanical breakage of the gradual wearA tool that no longer performs the desired function can be declared as failed Fig: e) Create wear & flank wearFig: (f) small & Larger Flank wear Typical wear pattern in cutting toolFLANK WEAR AND TIME RELATIONSHIPT hree stages o flank growth region (Break in region) state region (Temperature Insensitive region) failure (Temperature sensitive region)Flank wear formation depends on * Cutting Conditions (f, d, V, tool angles)* Properties of work material and tool materialFlank wear characterised by wear land (or Height) hfof wear band Fig: (a) Three stage flank wear curve, (b) Various elements of flank wear and crater wear, (c) Variation of various crater wear with time3 Temperature insensitiveareaTemperaturesensitive area12 Break in RegionTime (t) (min.)Flank Wear (mm), hfmmlCflfeTimehflfclfc(a)(b)(c)Tool wear Index, feed marks and surface finish Type of wear depends MAINLY on cutting speed Ifcuttingspeedincreases,predominantwearm aybe CRATER wearelse FLANK wear.

2 ,beforeflankwearlimitofhf= ( / 2), CDepth l tan 34, Nose RadiuskkCLACLAChlfWhereWidthfDiscefor HSS hfRRRRW here fFeedR Tool Flank WearTool MovementAmount of flank wearDepth of cutGenerated surfaceDesired surfaceAxisEffect of tool wear on machined component dimensions (Exaggerated view)Effect of tool wear on machined surfaceFLANK WEAR AFFECTS: * Dimensional accuracy* Process stability* Surface finishTOOL LIFE & MACHINABILITYTool no longer performs desired function failed Re-sharpen and use it LIFE: Useful life of a tool expressed in terms of time from start of a cut to termination point (defined by failure criterion). Sometimes also expressed in terms of no. Of the parts machined. Tool failure criterion depends on 1. The requirements of the component being produced. 2. Type of Operation: Roughing: force and power requirement. Finishing : Surface finish & dimensional accuracy. ,( 1 ) nttT Tool life MinutesnExponent for conditions testedCTaylor s constantCrepreVTCW heresents cutting speeVCuttid for minute as tool lifngSpeeed TAYLOR S TOOL LIFE EQUATION After 12 Years of ExperimentsDoes not account for:Feed (f)Depth of cut (d)Tool geometry (Rake Angle )Taking logarithm on both sidesLogV+ nlogT= LogCtThis becomes a straight line on the log-log scaleCutting Speed (m/min.)

3 LogTool life (minutes) Log1 Unitn= 1 (n<1), Ctis very largeTOOL LIFE & MACHINABILITYVTnfn1dn2=CN, n1, n2: Constants depending upon tool material (= to ).C: constant that depends on tool-work material combination and tool geometry (>100) VARIABLES AFFECTING TOOL LIFE Cutting Conditions (V, d, f) Tool Geometry (all six angles, and nose radius) Workpiece Material Cutting fluid MACHINE tool and Work piece region Tool concerned with workpiece material properties not the tool depends on workpiece material properties and good tool surface finish cutting forcesMachinabilityis defined as THE EASE WITH WHICH A GIVEN WORKPIECCE MATERIAL CAN BE MACHINED WIT A SPECIFIED CUTTING specification Apart from tool material, one has to give tool angles and tool nose radius in the following sequence while going to purchase or asking some one to make a tool : Tool specifications (all six angles, and nose radius) :7-8-5-6-9-4-1mm. Back rake angle (70), Side rake angle (80), End clearance (relief) angle (50), Side clearance (relief) angle (60), End cutting edge angle (90), Side cutting edge angle (40), Nose radius (1 mm)

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