Micrometer Range; How To Read A Micrometer; Standard Inch Micrometer - Polaris 1999 Sportsman 400 Service Manual

16
CHAPTER ONE
@
METRIC
VERNIER CALIPER
10.00 mm
+0. 50
rom
10.50 mm
o
1. Readin g on fixed scale:
2. Read ing on movable sca le:
Total reading :
' \10 mm
~ Fl xed
scale
\ :-----"i e
f----"==l-)
s:=J=-..
2
J
4 5 :
'!I""I""I"uli'- Il
I I I
! ': · : : .
I
i
lilt
' C :Jr
• , .\ ( Movable sc:' , e
0.50 mm
rea ds 0.001 in. (o ne one-thousandth) o f an inch.
Thus, eac h thi mb le mark is equal to 0.001 in. Every
fift h thimble mark is numbered to help with read-
ing : 0, 5. 15 and 20.
Reset the mi crometer so that the th imbl e and
s leeve lin e zero mark s align . T hen tum the thimble
co unterc loc kwise one complete re vo lution and
alig n the thimbl e ze ro ma rk with the fir st line in the
sleeve line. T he mi crometer now rea ds 0.025 in.
(twenty- five thou sand s) of an inc h. T hus, cach
s leeve line represents 0.025 inch.
Now tum the thimbl e co unterclockwi se while
co unting th e s leeve linc mark s. Every fourth mark
on the
sleeve line
is marked with a
number
ranging
from
one throu gh n ine. Manufacturers usuall y m ark
the
last mark on th e sleeve wit h
a O.
Thi s indi cat es
the end of the
micro me ter 's measuring ran ge.
Each
s leeve num ber rep rese nts 0.1 in. For exa mple, the
numbe r I represents 0.1 in. and the number 9 repre-
sents 0.9 inc h.
W hen read ing a sta ndard m icrometer. tak e th e
followi ng three m ea surements de scribed and add
the m togeth er.
Th e sum of the
th ree rea d ing s will
g ive the measurem ent in
a thousandth of an
inch
(0.00 1 in.).
To read a m icro me ter. perform the following
steps and refer to th e exam ple in Figure 24.
A micrometer 's
size
indicates the minimum and
maximum size of a part that
it
can measure. The
usual sizes are : 0- 1 in.(0 -25 m m) , 1-2 in.(25-50
m m), 2-3 in. (50- 75 mm) and 3-4 (75-100 mm ).
T hese mi crometer s lise fixed anv ils.
So me m icrometers use th e same frame with inter-
cha ngeable anvil s of
di fferent leng
ths. Thi s allows
the inst allation of the correct lengt h an vi l tor a par-
ticular j o b. For ex ample, a 0-4 in. inter ch ange ab le
micrometer is equipped w ith four d ifferen t len gth
anvi ls. While purchasing one o r tw o microm eters to
cover a ra nge
from
0-4 in,
or
0-6 inches is less
ex-
pensiv e, its overa ll
frame
size
makes
it less conve -
nien t to usc.
The sta nda rd inch micro meter is uccuratc to
one- tho usa ndth o f an inch (0 .00 1 in.) . T he heart of
the mi crometer is its spi nd le screw with 40 thread s
per inch . Eve ry tu m of the thi m ble
will
move th e
spindle 1/40 of an inch o r 0.025 inch.
Before lea rn ing how
1 0
read a m icrom eter, study
the
marki ngs and
part
nam es
in Figure 23. Tum the
mi crometer thimbl e until its zero mark alig ns wi th
the ze ro mark on th e sleeve line. Now tum the thim -
ble cou nterclockwise and a lign the next thimble
mark w ith
the
slee ve line. The mi crometer now
lion describes how to usc th e ou ts ide mi crometer.
Th e o utside m icrometer is the mos t com mo n typ e o f
micro meter used to service a veh icle, The outside
micrometer is also used to measure the dimension
tak en
by
a sm all hole gauge o r a tele scopi ng ga uge
describ ed later in this se ction.
Other types o f m icrometers include the d epth m i-
crometer and screw thread micrometer. Figure 23
illu strates the vario us pari s of the out sid e mi crome-
ter
with
its pa rt nam es and markings identified .
How To
Read a
Micrometer
l\lic romcter Range
Sta ndard inch micrometer
W hen read ing
a
m icrometer, number s
are
taken
from di ffere nt scales and add ed togeth er. Th e
fol-
lowing sections desc ribe how to read th e standard
inch m ic rom eter, the ve rnie r inch mi crom eter, the
standard metr ic mi cro met er and the m etr ic ve rn ier
m icrometer.