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DRILL BITSITARPENING

UNIT

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Drill Bit Sharpeningntroduction (Con't.) Pzge2Lip Angles- range rom 60 degees ncludedangle o 150degeesx'ith the generalpurposeor standardanglebeing 118degrees59degrees ff eachside of center.

Woo4 frber, hard rubber = 60 degreesDcep hole gun drills = ?0Aluminum alloys& die casts = mCopperurys = 100Softbronze, rass,molded = 118material, teel,plasticHard material,steelrails = 150

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AdvancedtletalMr. CasselTIIISTDRILLS

PARTS F A TI,IISTDRILL

SHANDRILLANGLES

FLUTE

cLEAR$:E NcLE

') YTpAIIGL FIGURE F GURE FIGUREPOINTSFDRILL RINDINGFul ly 95f , f the di f f icul t les encounteredn dr i l l ing arc due o improperpoint gr inding. overs ize, ough nd apered oles,chipping f the point ,breakagef the shaf t of the dr i l l are a fewof the di f f icul t ies caused ypoolgr inding.In gr indinga dr i l l , thrce hingsmustbe considered:

1 Lip clearance2. The engthandangleof the l ips3. lleb anglLip c learances the rel ief which s given he cut t ing edgesn order o al lowthen to enter the netal without interference, (SeeFlgureB) Theheel (thesurfaceof the point backof the cutting lip) shouldbe ground uay ron thecut t lng l ip at an angleof e ight to twelvedegrees, n al l cases, h ls anglels the angleat the c i rcunferencef the dr i l l .I f the angleof the l ip c learances too great , the edges f the cut t ing ipwi l l breakdown henhe dr i l l s tar ts to workbecauseheywi l l not havesuf f ic ient backingo support hem.I f unsuf f ic ient ur face s ground way, he c learance f the dr i l l point is soreducedhat it ceaseso be a cutting edgeand efuses o enter the metal.This condi t ionmay esul t in spl i t t ing the dr i l l up the center ,

LIP OFCUTTINGEDGE

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DEMONSTRATION NOTES AND THOUGHTS