CompleteTeardown,Cleaning,andReassemblyoftheOlympusBH‐2SlidingFocusBlock Revision2 Page7of23
process, and that any necessary personal protective
equipmentisutilizedtominimizeexposure.Consultthe
MSDSsheetbeforeusinganyunfamiliarsolvents.Many
of the solvents listed above are flammable and their
vapors may represent an explosion hazard if
mishandled.Whicheversolventsarechosen,besureto
follow all of
the manufacturer’s instructions and safety
precautions.
SolventCompatibilitywithPartsandFinishes
Many solvents will damage the finish of painted
surfaces(isop ro pylalcoholor409Cleanermaybesafely
usedto clean mostpaintedsurfaces) orwill dissolve or
damageplasticparts.Donotallowuntestedsolventsto
contact any plastic parts or any painted surfaces.
Before using a solvent to clean plastic
parts or painted
surfaces, test a small amount of the solvent in an
inconspicuous area (such as inside a plastic knob ) to
ensure compatibility with the plastic part or painted
surface.Never use xylene to clean nylon parts, as
xylene dissolves nylon.Isopropyl alcohol and
trichloroethylene will cause swelling of
nylon due to
solvent absorption.The list of solvents generally
considered safe for nylon includes acetone, diethyl
ether, heptane, mineral spirits, naphthalene, and
turpentine.
RecommendedLubricants
TheOlym pusBH2(BHS)repairmanual(seetheOriginal
Olympus Documentation section of this document)
recommends using grease in the sliding focus block
mechanism.However,basedondecadesofexperience
servicingBH‐2equipmentinthefield,somemicroscope
repair technicians recommend omitting the grease
entirelyfromtheslidingfocusblock,
inordertoreduce
the fouling of the mechanism which can occur if dust
anddebrisaccumulatesinthegreasedslides,aswellas
reducing any stiffness or sluggishness that will result
from thickening of the grease.Given this conflicting
guidance, consider that grease may be applied to the
slide
perthe Olympusguidance,attheriskofrequiring
more frequent maintenance to keep the mechanism
cleanandfreelymoving,andgreasemaybeomitted,at
the risk of more long‐term wear of the mechanical
components.Mobil Polyrex
TM
EM or Molykote® 44
(items 7 and 5 of Appendix 2) are recommended if
lubrication is desired in the slide.Regardless of
whether or notlubrication is used in the slide, aheavy
greasesuchasDowMolykote®111(item6ofAppendix
2)shouldbeusedtohold
theguiderailsinplaceduring
reassembly, and any excess grease remaining after the
guide rails have been installed should be thoroughly
removedbefore proceedingwiththereassemblyofthe
slidingfocusblockmechanism.
LabelPartsforIdentificationandReassembly
There are many small parts that make up the sliding
focus block mechanism.It is critical that these be
bagged and tagged as they are removed to prevent
them from getting lost and to facilitate their proper
identificationduringreassembly.
PartofaComprehensiveFocusOverhaul
Maintenance of the sliding focus block is best
performed as part of a comprehensive overhaul of the
entire focus mechanism.It is best performed after a
teardown of the coaxial focus mechanism has been
performed,since this serviceiseasier to perform while
the focus knobs and other focus parts are
not present
onthe arm.Accordingly,thisdocumentdescribes(and
theaccompanyingphotographs show)theservicebeing
performed on a stand that has had the coaxial focus
block completely disassembled, per the Complete
Teardown, Cleaning, and Reassembly of the BH‐2
Coaxial Focus Mechanism document.In almost every
casewhere
theslidingfocusblockissluggishandneeds
to be serviced, the coaxial focus mechanism is also in
need of a similar service, so it makes sense to perform
bothrepairsatthesametime.
ProtecttheExposedMountingDovetails
Before proceeding with the teardown described in this
document, cover the top of the microscope arm (i.e.,
the exposed mounting dovetails for the viewing head
and nosepiece, if applicable) with a clean plastic bag
andsecurethiswitharubberbandor adhesivetapeto
keep dust out (see Figure 2
).This is especially
important on BHSU and BHTU stands which have an
optical correction lens located just below the viewing
head to correct for the difference in tube length
introducedwiththereversednosepiece.
Figure2–Protectthetopofthearmfromdust
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