Drill bushes

Drill Bushes, different types of drill bushes, their materials, etc.

1. Drill Bushes
Prof. Ms. Amruta A. Rane
Assistant Professor,
DJSCE, University of Mumbai,
Mumbai.

2. Guidingthetools
•Toolsmaybeguideddirectlybytheplateorbycasehardenedsteelbushes.
•Bushesareusedtoguidedrills,reamers,boringtoolsandothercuttingtools.
•TheJigBushesshallsupporttoolswhichareslenderanddelicate.
•Bushesareininterferencefitinthedrillplate.

3. DrillBushes

4. MaterialsofBush
•BushesaremadeofhardenedCarbonSteelwith0.85-1%Carbon,0.5-0.9%
Manganese.
•TheyarehardenedtoRC60-64tominimisewearduetocontactwithhard,
rotatingtools.
•Bushesarefinishedbygrindingtheinsideandoutsidediameterswithin0.001
mmconcentricity.
•Theinsidediameterhasprecisionrunningfit(F7)withthedrill/reamer
•Theoutsidediameterismadepressfit(p6),precisionlocationfit(h6)orprecision
runningfir(f6)dependinguponapplicationofthebush.

5. PressFitBushes
•Theyaremostcommontypesofbushes
•Theyarepressedinterferencefitinthebushplates
•Usedforbatchproduction
•Havelongworkinglife
•Theyarealsousedaslinerforslipandrenewablebushes.
•Typesofpressfitbushes
oHeadedBush
oHeadlessBush
Headed collared press fit bushHeadless press fit bush

6. HeadedDrillBush
•Theyareusedtocontrolholedepth.
•Thecollarofthebushprovidespositivestopagainstthejigplate.Thecollaralso
preventsaxialmovementofthebushwiththedrill.
•Thebushiseitherplacedclosetotheworkpieceorfarenoughawayfromthe
workpiecetopermitswarftoescapebetweenitandtheworkpiece.
•Headeddrillbushesareprovidedwithseatingofthebushintheholeinthedrill
plateandundercuttingtheheadofthebush.
•Aleadisprovidedforeasyentryofthebushinthedrillplate.
Headed Drill Bush

7. HeadedDrillBush

8. HeadlessDrillBush
•Headlessdrillbushisusedwheretheholedepthisnotneededtobecontrolled
andnotimportant.
•Whenspacingofthebushiscloseorthetopsurfaceofthejigplateisrequiredto
befreefromtheprojectingcollars,headlessbushesareused.
Headless Drill Bush

9. HeadlessDrillBush

10. ExtendedDrillBush
•Itisusedwhentheholetobedrilledinafacethatisatsomedistancefromthe
drillplate.
•Whenthedrillbushislong,itsboreisrelievedsothatonlyendnearthe
workpiececontrolsthetool.

11. RemovableBush
Therearetwotypesofremovablebushes:
•Renewablebusharrangement
•Slipbusharrangement

12. RenewableBush
•Usedforcontinuousorlargebatchproduction
•Itisusedwhenthebushwearismoreandit
needtobereplacedfrequently.
•Headedorflangedbush
•Itcanonlybetakenoutoflinerbushby
removingtheretainingscrew.
•Flatisprovidedonthecollartoprevent
rotationandaxialmovementofthebush.The
flatarrestswiththecollaroftheretainer
shoulderscrew.
•Theoutsidediameterisprecisionlocationfit
(h6)

13. RenewableBush

14. RenewableBush

15. RenewableBush

16. SlipBush
•Theyareusedwhentwoormore
operationsareperformedonthesame
axissuchasdrillingandreaming,itis
necessarytousetwodifferentguide
bushesfordifferenttools.
•Headedorflangedbush
•SlipbushisusedwithLinerbush.
•Slipbushisusedwhenquick
changeoverisrequired.
•Retainingscrewisprovidedtoprevent
therotationoftheslipbush.
•Flatisprovidedonthecollarand
circularcut-outintheflangeto
facilitatequickassemblyandremoval.

17. SlipBush
•Thestraightflatisreplacedbyacircularstep.
Slip Bush

18. SlipBush

19. SlipBush

20. SlipBush
•Theheadoftheslipbushisfittedwitharod.
Slip Bush

21. LinerBushes
•Sometimesthesebushesarealsoknownasmasterbushing.
•Theyarepermanentlyfixedtothejigbody.
•Theyactasguidesforrenewabletypebushing.
•Theymaybebusheswithorwithouthead.

22. ThreadedBushes
•Thesebushesarethreadedontheoutside.
•Linerisusedtolocatethreadedbushinjigplate.
•Agrubscrewisprovidedtopreventaxialrotationofthelinerbush.
•Adrillbushcanbeusedtolightlyclamptheworkpieceintheregionofcutting.
•Theaxisofthedrillbushislocatedpositively.
Threaded Drill Bush

23. SpecialBushes
•Atwistdrilltendstoslidedowninclines
andcurves.Thiscausesbendingand
breakageofthedrill.
•Thisproblemcanbecounteredbyaltering
theshapeofthebushtoprovidebetter
supportandresistanceagainstbending.
•Bushmatchingtheendoftheprofileof
theworkpiece.

24. SpecialBushes
•Specialbushesareusedforawkwardworkpiece.
•Adrillbushisshapedtopreventdrillrunduetotheslopingworkpieceface.

25. SpecialBushes
•Sometimesthecentreofthe
drilledholesareplacedsocloseto
eachotherthatitisimpossibleto
provideanydrillbushesinthejig
plate.
•Undersuchcircumstances,a
combinedplate-typeofbushis
used.
•TheplatebushismadeofTool
Steel.
•Anumberofbushescanbe
combinedintoasingleplatebush.
Theplatebushisscrewedand
dowelledtothejigplate.

26. Summary
•DrillbusheshaveG7/F7holetoguidethedrill.
•DrillbushesaremadeofSteelhardenedtoRC62/65.
•Pressfitbushesareusedforshortruns.
•Renewablebushisusedforhighwearapplication.
•Slipbushesareusedformultipleoperationslikedrilling,reaming,counter-boring.
•Threadedandspring-loadedbushestocombineclampingwithguiding.
•Specialbusheswithendshapedareusedtopreventdrilldeflection.
•Platebushescombiningtwoormorebushesforverycloselyspacedholes.

27. References
1.JigandFixtureDesignManual,ErikK.Henrikson,IndustrailPress.
2.JigsandFixture,P.H.Joshi,THM.
3.AnintroductiontojigandtoolDesign,M.H.A.–Kempster,IIIEd.PubELBS.

28. Thank You!