Micrometer Accuracy Check - Polaris 1999 Sportsman 400 Service Manual

Sleeve
20
o
5
20
15
Thimbl e
1. Reading on upper sleeve Hne
2. Reading on lower sleeve line
3. Thimble line coinciding with
sleeve line
Total reading :
CIIAPTER Ol'\E
5.0 mm
0.50 m m
0,18 mm
5.68 mm
Sleeve : Thimble
T he thimbl e scale is divided into fifty graduat ions
w here o ne graduatio n is eq ual to 0.0 I
111111 .
Every
fift h graduatio n is numbered to he lp w ith read ing
from 0-4 5. Th e thimble edge is used to indicate
which sleeve marking s to read .
To read the metri c microm eter add the num ber of
mi llimeters and half-mi llime ters on the sleeve line
to the nu mber of one-hund redth milli meters on the
thimbl e. To do so, perform the followin g steps and
refer to the example in Figure 28 :
I . Take the first reading by co unting the number of
marks visible on the upper slee ve line. Record the
reading.
2. Loo k below the slee ve line to see if a lo wer mark
is visible directly past the upp er line mark. lf so, add
0.50 to the firs t rea ding.
3. Now read the thimble mark that ali gn s w ith the
sleeve line. Record this reading.
NOTE
If
a thimble mark does not align ex-
actly with
the
sleeve line
b ill
falls he-
tween the twu lines, es timate the
deci mal amount between the lines.
For an accurate reading. a metric
vernier microm eter must be used.
4. Adding the micrometer readi ngs in Step s I. 2
and 3 gives the actual measurement.
,'\!etric vernier microm eter
A metric micrometer can accurately measure to
two -thousandths o fa mill imeter (0.002 mm). Whi le
it has the same markings as thc standa rd metri c mi-
cro meter. a vernier scale scribed on the slee ve
(Fig-
ure 29) makes it uniqu e. The vern ier scale consists
of five equally s paced lines 0, 2, 4, 6 and 8. T hese
lines run parallel on the to p of the sleeve where each
line is equa l to 0 .002 mm.
To read the metric vernier micrometer, perform
the following steps and refer to the exam ple in Fig-
ure 30 :
I. Read the metric vernier micrometer the same
way as wi th the standard metric micrometer. Thi s is
the initia l read ing .
2. If a thimble mar k aligns exactly wi th the sleeve
line. read ing the ve rnier sc ale is not necessary. If a
thimble line docs not a lign exact ly w ith the sleeve
line, read the vern ier sca le in Step 3.
3. Read the vernier scale to find whi ch mark aligns
with o ne thimble mark. The number of the vern ier
mark is the nu mber of thou sand s of a millimeter to
add to the initial reading taken
in Step I.
I\1icro mete r Acc ur acy Check
The micrometer must be checked frequen tly to
assu re acc uracy as follo ws: