CompleteTeardown,Cleaning,andReassemblyoftheOlympusBH‐2SlidingFocusBlock
Revision2 Page6of23
Introduction
The microsco pesin theOlympus BH‐2line(BHS, BHSU,
BHT, and BHTU) have largely been replaced in the
professional and clinical world, due to their advancing
ageandthelackofrepairpartsfromOlympus.Agreat
manyofthesemicroscopes wereproducedintheirday,
and because of this
are they readily available on the
usedmarketforveryreas onableprices.Thankstotheir
excellent build quality and solid optical performance,
these scopes are now very popular with hobbyists,
providing an affordable, high‐quality alternative to the
Chinese‐made scopes prevalent today.One problem
that might be encountered when
purchasing one of
thesescopesisthatthefocusactionmaybestiffdueto
the decades‐old grease in the coaxial focus mechanism
andintheslidingfocusbl ockmechanism.
ScopeofthisDocument
This document describes the complete teardown,
cleaning, and reassembly of the sliding focus block
mechanism in an Olympus BHTU stand.Since the
variousBH‐2standsusethesamesliding focusblockas
the BHTU, this document should allow a hobbyist with
reasonable mechanical abilities to service the sliding
focus block
on any of the BH‐2 stands.Note that this
document covers the specific configuration of the
sliding focus block mechanism which utilizes crossed
rollers to provide smooth linear motion of the focus
block.The vast majority of the BH‐2 stands that were
everproducedusedthismechanicalconfiguration.
The
veryearlystandsthatweremanufactured(i.e.,thefirst
200 or so) utilized bearing balls instead of crossed
rollersintheslideme chanism,andtheseearlyunitsare
outsidethescopeofthisdocument
1
.
ACautionRegardingStiffFocusMechanisms
Avoid turning the focus knobson anyBH‐2 microscope
stand whose focus mechanism feels abnormally stiff.
Turning these knobs when there is excess resistancein
themechanism,suchasmaybecausedbydriedgrease,
putshighstresses ontheplasticdrive gears inthefine‐
focus mechanism, and these
can be damaged if these
stressesaretoohigh.
ToolsNeeded
The followin g tools will be needed to complete the
teardown,cleaning,andreassemblyoftheslidingfocus
blockmechanisminaBH‐2microscopestand:
Allenwrenchordriver:2.5mm(item1ofAppendix2)
1
Afuturerevisionofthisdocumentmayincludetheball‐slideconfiguration,
ifasuitablestandeverbecomesavailableforthispurpose.
Allenwrenchordriver:4.0mm(item2ofAppendix2)
Allenwrenchordriver:5.0mm,(item3ofAppendix2)
Screwdriverset,JIS(item4ofAppendix2)
AFewWordsaboutJISScrews
Screws with JIS heads are frequently found in much of
the equipment designed and manufactured in Japan.
JISscrews lookvery much likestandard Phillipsscrews,
but they differ in that JIS screws weredesigned to not
cam‐out under torque, whereas Phillips screws were
designed to intentionally cam‐out as
a means to limit
the torque applied to the fasteners.Because of this
crucial difference in the geometry of the two screw
types, JIS screws will be damaged by standard Phil lips
drivers if too much torque is applied.JIS screws can
usuallybe identifiedby thepresenceofasingle
dot(or
by an “X”) stamped into one of the four quadrants of
thecross‐pointdepression(seeFigure1).
Figure1–HeadofatypicalJISscrew
SuppliesNeeded
The following supplies will be needed to complete the
teardown,cleaning,andreassemblyoftheslidingfocus
blockmechanisminaBH‐2microscopestand:
Cleaningsolvents(seeRecommendedSolventsbelow)
Cottonswabs
Lubricants(seeRecommendedLubricantsbelow)
Tissues,oilfree
RecommendedSolvents
Sometypeofcleaningsolventwillbene ededtoremove
the old grease from the various components of the
sliding focus block mechanism.Solvents that can be
used are acetone (commonly sold as fingernail polish
remover), diethyl ether, heptane, hexane, min eral
spirits,turpentine,andxyle ne.
SafetyConsiderationswithSolvents
Regardless of which solvent is chosen, make sure that
adequate ventilation is present during the cleaning
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