Complete
Teardown,
Cleaning,
and
Reassembly
of
the
Olympus
BH
‐
2
Sliding
Focus
Block
Revision
2
Page
6
of
23
Introduction
The
microscopes
in
the
Olympus
BH
‐
2
line
(BHS,
BHSU,
BHT,
and
BHTU)
have
largely
been
replaced
in
the
professional
and
clinical
world,
due
to
their
advancing
age
and
the
lack
of
repair
parts
from
Olympus.
A
great
many
of
these
microscopes
were
produced
in
their
day,
and
because
of
this
are
they
readily
available
on
the
used
market
for
very
reasonable
prices.
Thanks
to
their
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
these
scopes
is
that
the
focus
action
may
be
stiff
due
to
the
decades
‐
old
grease
in
the
coaxial
focus
mechanism
and
in
the
sliding
focus
block
mechanism.
Scope
of
this
Document
This
document
describes
the
complete
teardown,
cleaning,
and
reassembly
of
the
sliding
focus
block
mechanism
in
an
Olympus
BHTU
stand.
Since
the
various
BH
‐
2
stands
use
the
same
sliding
focus
block
as
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
ever
produced
used
this
mechanical
configuration.
The
very
early
stands
that
were
manufactured
(i.e.,
the
first
200
or
so)
utilized
bearing
balls
instead
of
crossed
rollers
in
the
slide
mechanism,
and
these
early
units
are
outside
the
scope
of
this
document
1
.
A
Caution
Regarding
Stiff
Focus
Mechanisms
Avoid
turning
the
focus
knobs
on
any
BH
‐
2
microscope
stand
whose
focus
mechanism
feels
abnormally
stiff.
Turning
these
knobs
when
there
is
excess
resistance
in
the
mechanism,
such
as
may
be
caused
by
dried
grease,
puts
high
stresses
on
the
plastic
drive
gears
in
the
fine
‐
focus
mechanism,
and
these
can
be
damaged
if
these
stresses
are
too
high.
Tools
Needed
The
following
tools
will
be
needed
to
complete
the
teardown,
cleaning,
and
reassembly
of
the
sliding
focus
block
mechanism
in
a
BH
‐
2
microscope
stand:
Allen
wrench
or
driver:
2.5mm
(item
1
of
Appendix
2
)
1
A
future
revision
of
this
document
may
include
the
ball
‐
slide
configuration,
if
a
suitable
stand
ever
becomes
available
for
this
purpose.
Allen
wrench
or
driver:
4.0mm
(item
2
of
Appendix
2
)
Allen
wrench
or
driver:
5.0mm,
(item
3
of
Appendix
2
)
Screwdriver
set,
JIS
(item
4
of
Appendix
2
)
A
Few
Words
about
JIS
Screws
Screws
with
JIS
heads
are
frequently
found
in
much
of
the
equipment
designed
and
manufactured
in
Japan.
JIS
screws
look
very
much
like
standard
Phillips
screws,
but
they
differ
in
that
JIS
screws
were
designed
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
Phillips
drivers
if
too
much
torque
is
applied.
JIS
screws
can
usually
be
identified
by
the
presence
of
a
single
dot
(or
by
an
“X”)
stamped
into
one
of
the
four
quadrants
of
the
cross
‐
point
depression
(see
Figure
1
).
Figure
1
–
Head
of
a
typical
JIS
screw
Supplies
Needed
The
following
supplies
will
be
needed
to
complete
the
teardown,
cleaning,
and
reassembly
of
the
sliding
focus
block
mechanism
in
a
BH
‐
2
microscope
stand:
Cleaning
solvents
(see
Recommended
Solvents
below)
Cotton
swabs
Lubricants
(see
Recommended
Lubricants
below)
Tissues,
oil
free
Recommended
Solvents
Some
type
of
cleaning
solvent
will
be
needed
to
remove
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,
mineral
spirits,
turpentine,
and
xylene.
Safety
Considerations
with
Solvents
Regardless
of
which
solvent
is
chosen,
make
sure
that
adequate
ventilation
is
present
during
the
cleaning
