Stanley Black & Decker MBX138 Automobile Parts User Manual


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PROPER USE & CARE OF TOOL BITS
18 ► MAXFORCE BREAKER User Manual
Initsmostextreme forms,thecombinationofsurface
damageandseverebendingcanquicklybreakeventhe
bestworkingsteels.
Theillustrationsbelowshowexamplesofseverestress
breaks.
Figure15.SevereStressBreaks
PRYING
This is the most common causeof toolfailure. Even
whenthereisnosurfacedamage,thestressfrompry-
ingcaneasilybreakaworkingsteel.Thiskindoffailure
generallyresultsfromanytypeofsidepressuresuchas
anincorrectbreakingangleorfromusingthetooltore-
positionmaterial.Thetoolshouldnotbeusedasapivot
pointwhenrepositioningthecarrier.Thepowergener-
atedbythecarrierwillfarexceedthestrengthofthetool.
Figure16.PryingDamageExample
Similarfailurescanalsooccurwhenthesteelisused
with extreme down pressure, and the steelrepeated-
lyslipsofftheworkatanangle,orthematerial,itself
movesfromundertheworkingsteel.
Figure17.ExtremeDownPressureBreakage
Asthenextillustrationshows,fatiguefailurestakemany
forms,buttheyallexhibitsimilarfeatures.Generally,the
brokensurfaceisbrittleandhasa“lip”likethatinthe
bendingfailure,eventhough,insomecases,theliphas
beenbroken.
Figure 18. Fatigue Failures
CORROSION
Toolsshouldbegreasedandstoredoutoftheweather.
Corrosiontendstoacceleratethefatiguefracturesofthe
tool.
MUSHROOMING
Drivingthetoolintoahardmaterialforalongperiodof
timegeneratesanintenseheat,indicatedbyabluetone
justabovethepoint.Thiswillsoftenthesteelandcause
thepointtofoldoverormushroomtheendofthetool.
Avoidhammeringinonelocationfortoolong.Ifmaterial
doesnotbreakafterashortperiod(approximately15to
20seconds),repositionthetool.
Figure 19. Mushrooming
If the overheated steel is suddenly cooled by being
dipped in standing water, for example, the metal will
hardenandbecomebrittle.Thesearesomeexamples
offailurecausedbytemperchangesoccurringonthe
job.
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