INTRODUCTION
Basicinstructions-ChainWearTables-RollerChains
Chainwear
Theindividualjointsinarollerchainarticulateastheyen-
terandleavethesprockets.Thisarticulationresultsin
wearonthepinsandbushings.Materialthatiswornaway
fromthesesurfaceswillcausethechaintograduallyelon-
gate.Chainsdonotstretch.Materialiswornfrompinand
bushing.
Criticaldimensionsofthechainareasfollows:
•
(1)2Xpitch
•
(2)Wearplus2Xpitch
•
(3)Elongationduetopinandbushingwear
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Elongationisnormalandmaybeminimizedbyproper
lubricationanddrivemaintenance.Therateofwearis
dependentupon:therelationshipbetweentheloadand
theamountofbearingareabetweenpinandbushing,the
materialandsurfaceconditionofthebearingsurfaces,the
adequacyoflubrication,andthefrequencyanddegree
ofarticulationbetweenpinsandbushings.Thelatteris
determinedbythequantityofsprocketsinthedrive,their
speeds,thenumberofteethandthelengthofthechain
inpitches.
Anaccuratewearmeasurement(1)canbemadebyus-
ingtheaboveillustration.Measureascloselyaspossible
fromthecenterofonepintothecenterofanother.The
morepitches(pins)containedwithinthemeasurementin-
creasetheaccuracy.Ifthemeasuredvalueexceedsthe
nominalbymorethantheallowablepercentagethechain
shouldbereplaced.Themaximumallowablewearelon-
gationisapproximately3%formostindustrialapplica-
tions,baseduponsprocketdesign.Theallowablechain
wearinpercentcanbecalculatedusingtherelationship:
200/(N),where(N)isthenumberofteethinthelarge
sprocket.Thisrelationshipisoftenusefulsincethenor-
malmaximumallowablechainwearelongationof3%is
validonlyupto67teethinthelargesprocket.Indrives
havingxedcenterdistances,chainsrunninginparallel
orwheresmootheroperationisrequired,wearshouldbe
limitedtoapproximately1.5%.
Forexample,if12pitches(12pins)ofa#80chainwere
measuredandtheresultwas313.944mm(12.360in)or
greater(using3%asthemaximumallowablewear),the
chainshouldbereplaced.Anythinglessthan313.944
mm(12.360in)wouldstillbeacceptablebymostindus-
trialstandards.
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