Drill Bit Sharpening

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DRILL BIT SITARPENING

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UNIT

Drill Bit Sharpening Introduction For Ouiz Purooses: Read Unit 34-12- 15 and ac.companying handouton drill bit sharpening. Reminder: AII anglesground servetwo purposes: . .

Relief SuPPo.rt

Partsof the TaperShankT$ist Drill: (SeeDitto Handoutasyou read) Tang- is the flat on the end of the tapershankthat will be usedto drivethe drill. This targ will fit into the slot in a spindleor sleeveadaptor. TaperedShank- The area betweenthe tang and the identificationband. Ir is responsiblcfor alignmentof the drill. The tapor can be anyoneof several- Morsewhichis 5/8"per foot, Brown& Sharpewhichis 12" per foot, Jarno,National,R-8,etc. (Thereare manydifferenttapers that haveand do existin the UnitedStatestoday. The mostcommon one in this shopis Morse.) knd - Thisis the narrowspiraledsurfacebetweenthe fluteandthe reliefon a drill. This is the only part of the drill that touchesthe wall of the whole while drilling. Relief- This is the wide spiralgdsurfacebetweenthe flute and tho land. It serves as the majorityof the crosssectionalstrengthof the ddll and the stength of tbe cuttingedge. Flute - The flutes are the groovesin the drill. Without the flute there would be no cutting odge. The flutes also sorveas a path for the chipsto exit and the coolantto enter, Web - The web is the vcry center of the drill. It increasesin thicknessfrom the original length of the drill as it progressestoward the shank. Older d lls that havebeen sharpenedmanytimes,must havean operation performedon them known as "thinning the web." Ask and watch to seethis in the demonstration on drill bit sharpening.

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Drill Bit SharpeningIntroduction (Con't.)

Pzge2

Lip Angles- rangefrom 60 degees includedangleto 150degeesx'ith the general purposeor standardanglebeing 118degrees(59 degreesoff eachsideof center. Woo4 frber, hard rubber Dcep hole gun drills Aluminum alloys& die casts

= 60 degrees = ?0 = m

Copperaurys

= 100

Softbronze,brass,molded material,steel,plastic Hard material, steel rails

= 150

= 118

Advancedltletals Mr . Cassel

TIIISTDRILLS PARTS OFA TI,IISTDRILL

SHAN

FLUTE

L IP OF CUTTING EDGE

DRILLANGLES

')"Y cLEAR$:E ANcLE

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AIIGL E FIGURE A

FIGUREB

FIGURE C

POIN TS OFD R ILLGR IN D IN G Fu l l y 9 5 f,of the di ffi c ul tl es e n c o u n t e r eind d r illin g a r c d u et o im p r o p e r p o i n t g r i ndi ng. ov ers i z e,rou g ha n dt a p e r e dh o le s , c h ip p in go f t h e p o in t, b re a ka goef the s haft of the dr ill a r e a f e w o f t h e d if f ic u lt ie s c a u s e dby p o o l g rindi ng. In g rin d i nga dri l l , thrc e thi n g s m u s tb e c o n s id e r e d : 1. Li p c l earanc e 2. The l engthan da n g leo f t h e lip s 3. lleb angle L ip cle a ranc ei s the rel i ef w h ic his g iv e nt h e c u t t in g e d g e sin o r d e r t o al l o w then to enter the netal without interference, (SeeFlgureB) The heel, (the surfaceof the point backof the cutting lip) shouldbe groundauayfron the cu ttl n g li p at an angl eof ei g h t t o t we lv ed e g r e e s , I n a ll c a s e s ,t h ls an g l e ls th e a n gl eat the c i rc unfere n coef t h e d r ill. If th e a n gl eof the l i p c l eara n c eis t o o g r e a t , t h e e d g e so f t h e c u t t in g li p w i l l b r e a kdow nw henthe dri l l s t a r t s t o wo r kb e c a u steh e y will n o t h a v e su ffi cie n t bac k i ngto s upportt h e m . If u n su f fi c i ents urfac ei s gro u n da wa y ,t h e c le a r a n c e o f t h e d r ill p o in t i s so reducedthat it ceasesto be a cutting edgeand refusesto enter the metal. Th i s co n d i ti onmayres ul t i n s p lit t in g t h e d r ill u p t h e c e n t e r ,

DEMONSTRATION NOTES AND THOUGHTS