Drill Nomenclature And Geometry - NEMES

DrillDrill NomenclatureNomenclatureandand GeometryGeometry

DrillDrill NomenclatureNomenclature Drill Construction:A twist drill is made up of three components:– Shank– Body– Drill point

Drill BodyRakeorHelix AngleWidth ofLandBodyClearanceHeelFlutesWidth of landLandLeading Edgeof the LandBack Taper

DrillDrill NomenclatureNomenclature Cutting Diameter:“Largest diameter measured across thetop of the lands behind the point” Back Taper– The diameter reduces slightly toward the shankend of the drill, this is known as “back taper”– Back taper provides clearance between the drilland workpiece preventing friction and heat

Drill Flutes

DrillDrill NomenclatureNomenclatureFlute Length:“The length of flute measured from the drillpoint to the end of the flute runout”– Flute length determines the maximum depth ofdrilling

DrillFlute ConstructionConstructionDrill NomenclatureNomenclature- FluteParabolicConventionalChipbreaker

DrillFlute ConstructionConstructionDrill NomenclatureNomenclature- Flute Conventional:– Has “J” shaped flute geometry– Used in a wide variety of soft andhard drilling applications– Drill up to 3 to 4 diameters beforepecking– Most drills in the industry havethis type of construction

DrillFlute ConstructionConstructionDrill NomenclatureNomenclature --Flute Chipbreaker Has special tight radius“J” shaped flute Tight radius helps tobreak up chips Heel is rolled forincreased chip space Used in equipment withfixed feeds where longstingy chips areproduced

DrillDrill NomenclatureNomenclature- FluteFlute ConstructionConstruction Parabolic:“Compound radius,cleared heel flute shape”Parabolic flutessubstantially increaseavailable flute spacefor chips!

DrillDrill NomenclatureNomenclatureLand: “The part of the drill bodybetween the flutes”– The lands provide the drill withmuch of its torsional strength– Reducing the land width increaseschip space, but reduces strength

Drill Webs

Drill-WebsDrill NomenclatureNomenclature -Webs“The thicknessmeasuredacross thebase of theflutes”– Contributesto thetorsionalstrength ofthe drill

DrillDrill NomenclatureNomenclature Web ThicknessWebs normally fall into three categories:– Light– Medium– Heavy

WebWeb ty

DrillWeb ThicknessThicknessDrill NomenclatureNomenclature- Web Light:– Generally 14 to 16 % ofthe cutting diameter– Found on fast helixgeneral purpose drills– Weakest of the drillwebs

DrillDrill NomenclatureNomenclature- WebWeb ThicknessThicknessMedium– Typically 17 % to 22% of thecutting diameter– Found on all GP drills

DrillWeb ThicknessThicknessDrill NomenclatureNomenclature- Web– Heavy– Generally 25 % to 40% of the cuttingdiameter– Used on cobalt, coolant hole, parabolic,and other heavy duty drills

DrillWeb ConstructionConstructionDrill NomenclatureNomenclature- Web There are three common webcontructions:– Tapered– Parallel (Pre-thinned )– Parallel-Tapered

WebWeb ConstructionsConstructionsParallel Web - ThinParallel Web - HeavyThinned Web thenParallelConstant Increase

Effects of Drill Re-SharpeningWeb thicknessAASectionA-AChisel edgelengthBBDrillDiameterWeb thicknessChiseledge lengthSectionB-BDrillDiameter

Web Thinning Drill webs are non-cutting– Don’t contribute to thecutting process– They consume powerand torque to movethrough the work piece– Must reduce the chiseledge length to be asshort as possible inlength!Ground notch tothin web andreduce chiseledge length

Web/Point ThinningNo ThinningNo thinning asreceived from themanufacture.ConventionalStock is removedin such a wayas to followthe flute contour.

Web/Point ThinningSplit PointTwo secondary back-offgrinds, adjacent tothe chisel and almostto centerHigh TensileNotchedNotched point resultsin centering abilityand reduction of forces

Web/Point ThinningFlatted LipTypeFlatting the faceof the flute,Eliminates“hogging-in”Gash TypeGrinding two half-roundgashes near the centerof the drill

Web Thinning“ K” Notch Half radius notch– Web is typically thinned to 8% to 12 % ofthe drill diameter– Shortens chisel edge length reducingthrust– Improves chip evacuation– Used in tougher materials and some largediameter drills

Web Thinning“R” Notch Full radius notch– Web is typically thinned to 8% to 12 % ofthe drill diameter– Shortens chisel edge length reducingthrust– Improves chip evacuation– Used primarily on coolant hole drills

Drill Helix Angles

DrillDrill NomenclatureNomenclature Helix Angle:“Angle formed between a linedrawn parallel to the axis of thedrill and the edge of the land”

VariousVarious HelixHelix AnglesAnglesHigh Helix AngleRegular Helix AngleSlow Helix Angle

DrillHelix AngleAngleDrill NomenclatureNomenclature- HelixHelix angles generally fall into three categories:– Slow Spiral– Regular Spiral– Fast Spiral

DrillHelix AngleAngleDrill NomenclatureNomenclature- HelixSlow Spiral– 12 to 22 helix angle– Used in materials producing broken chips suchas brass or bronze, or cast iron– Also used in horizontal applications where thedrill is not rotating

DrillHelix AngleAngleDrill NomenclatureNomenclature- HelixRegular–––28 to 32 helix angleFound on most general purpose and cobalt drillsUsed in a wide variety of drilling applications

DrillDrill NomenclatureNomenclature- HelixHelix AngleAngleFast Spiral– 34 to 38 helix angle– Used on high helix general purpose and deephole parabolic drills– For softer ferrous and non-ferrous materialsproducing stringy chips

DrillHelix AngleAngleDrill NomenclatureNomenclature- Helix How does changing the helix angleeffect performance?Fast Spiral Drills– Provides greater lifting power for chips, but areweaker– Generally used in deep holesSlow Spiral Drills– Are stronger, but have less lifting power for chips– Generally limited to shallow holes

VariousVarious HelixHelix AnglesAnglesRegular HelixDrillHigh Helix Drill

Drill Margins

DrillDrill NomenclatureNomenclature Margins:“The cylindrical portion ofthe land that is not cutaway to provide clearance”– The balance of the land isreduced in diameter, knownas “cleared diameter” or“body clearance”– Body clearance preventsexcessive rubbing andfriction

leMargin

DrillDrill NomenclatureNomenclature- MarginsMargins– Single Margin: Has one margin adjacent tothe cutting edge Single margins create theleast amount of rubbing andfriction with minimal supportin the hole Most standard tools aresingle margin

DrillDrill NomenclatureNomenclatureDouble Margin: Has a margin at both the cutting edge andheel Used in specialized applications whereprecision hole size, and finish are required The additional margin adds stability andreduced the possibility of chatter, but createsmore friction Often used when drilling through a bushingfor support

DrillDrill NomenclatureNomenclature Triple Margin: Has three margins per land, one at the cutting andheel and one in the middle of the land Used where very high precision and hole size isrequired Provides the greatest amount of stability and thegreatest amount of friction and rubbing

Drill Points

DrillPointsDrill NomenclatureNomenclature- Points The drill points has four mainfeatures:– Point Angle– Cutting Lips– Chisel Edge– Lip Relief

Drill Point Angles118 118 118 45 General purposeChamfer(to reduce burr)90 118 140 Split(reduce thrust &self centering -NC)High alloyedsteelsSoft and ductilematerialHelical Point(self centering)

DrillNomenclature Point AngleShorter, flatter cutting lipsproduce narrow chipsHigh Point Angle (Flatter Point)– Recommend for harder and toughermaterials– Stronger cutting edges– Shorter cutting lip produces a narrower chip– Point angle greater than 130 are generallyused in materials that have been hardened orare extremely tough

DrillNomenclature Point AngleLonger cutting lipsproduce wider chipsLower Point Angle (Sharper Point)– For softer materials– Points sharper than 118 are generallyused for soft non-ferrous materials andnon-metallic

Drill Nomenclature Cutting Lips“Cutting edges that extend fromthe center of the drill to theouter diameter”– On most standard drills, thecutting edge should form astraight line– Some specialty and highperformance drills have curvedcutting lips

Drill Nomenclature- Points Elements of Drill Points Lip Relief Angle– Varies with the diameter of the drill and hardnessof the material– On larger diameters and drills for harder materials,lip relief is decreased to as low as 8 – Drills for soft materials and small diameters havehigh relief angles up to 24 – Lip relief angles are measured across the marginwidth

Incorrect Lip ClearanceExcessive No lipclearanceExtreme pressurerequired to make drillcut; top of drill showssigns of rubbing andheat caused by little orno lip clearanceCorners of drillbroken due toexcessive lipclearance

Suggested Lip Relief AnglesDrill Diameter RangeLip Relief Angle#80 to #61#60 to #41#40 to #311/8 to 1/4 F to 11/32 S to 1/2 33/64 to 3/4 49/64 and larger24 21 18 16 14 12 10 8

Drill Nomenclature Chisel Edge“The edge at the end of the web, thatconnects the cutting lips”– The chisel edge does not cut - itpenetrates displacing the workpiecematerialThe chisel edge consumes 60% to 70%of the thrust required!

Drill Nomenclature Chisel Edge Angle“The angle formed between thechisel edge and the cutting lips”lips– The chisel edge angle is generally125 to 135 “Chisel edge angle is an indicationof lip relief”4:00

Drill Nomenclature- Points 118 Degree– General purpose point– Used in a wide variety ofnon-hardened Materials– Most common drill pointused in the industrySingle primary clearanceground in oneoperationCuttinglips

Drill Nomenclature- Points 118 Four Facet– Generalpurpose point– Used primarilyon solidcarbide drills– Facets provideprimary andsecondaryrelief grinds tomaintain earance

Drill Nomenclature- Points135 or 118 degree Double Angle:90 degrees– 118 or 135 point with a 90 outerchamfer– Similar to a Racon, but is easier toregrind– Minimizes outer corner wear– Helps to eliminate burrs on breakthrough

DrillPointsDrill NomenclatureNomenclature- Points– 90 Degree90 degrees included– Generally used for soft non-ferrousmaterials and non-metallic– Occasionally used in soft cast iron

Drill Nomenclature- Points Helical– Superior self centering point– Chisel has “S” shape and crown toproduce the self centering feature– Produce accurate hole size with goodfinish– Excellent for producing straight holesin deep hole applications– Minimizes burrs on breakthrough

Drill Nomenclature- PointsLong radius Cutting lips Racon– 118 point with corner radius– Prevents “grabbing” when exiting angledor curved surfaces– Reduces outer corner wear– Minimizes burrs on breakthrough– Allows for increased feed rates

Drill Nomenclature- Points Bickford point:– Combination Helical and Racon point– Has helical “S” chisel with cornerradius– Self centering point– Prevents “grabbing” when exitingangled or curved surfaces– Reduces outer corner wear– Reduces burrs on breakthrough

Drill Nomenclature- PointsSecondaryclearance Split Point: (Crankshaft)– Self centering point– Minimizes chisel length,reduces thrust– Split produces positive rakeangle improving the chipcutting ability at the center ofthe drill point– 118 and 135 are the twomost common split points– Extremely good for off handoperationsPrimaryclearanceCutting lip

Drill Nomenclature- Points 135 Four Facet SplitPoint– Heavy duty point forhard and toughmaterials– Used primarily on solidcarbide drills– Facets provide primaryand secondary reliefgrinds to maintainedge strength– Split self centers andreduces thrust

Drill Nomenclature- Points Flat Bottom: Has 150-180 end to create flat bottom holes– Bushings– “Press fit” parts Generally used with drill bushings toprevent “wandering” and chatter