The Outside Micrometer
Parts of The Metric and Imperial
micrometer
1
Metric micrometer
sleeve
anvil
thimble
spindle
ratchet
lock
frame
Scale
Sleeve
The Imperial micrometer Sleeve
Has 40 graduations along its length of 1
inch
Each graduation is 1/40 of an inch
=0.025inches
Every 4th graduation is larger =1/10 of
an inch or =0.1 inch
Sleeve
The metric micrometer sleeve has a total
length of 25 mm
The sleeve is broken down in 5 main sections
of 5 mm each
Every 5mm section is further broken down to
give 10 equal segments with each =0.5mm
Therefore there are 50 divisions on the sleeve
The Thimble
This is the part that is turned
The imperial scale has 25 graduations
around the the thimble scale that is
numbered 0-25
Each graduation =0.001 inches
This gives accuracy to 0.001 inches
The metric thimble
This has the part that is rotated
Contains a scale that is around the
outside of the thimble
It has 50 divisions numbered 0-50
Each division is 0.01 mm
This gives accuracy to 0.01mm
The Ratchet
Located at the end of the thimble
Used to control the force or load applied to
the micrometer or the work being measured
Prevents the micrometer from being over
tightened
When max load reached it will make a
clicking sound. Some types use a sliding
clutch
The spindle
The spindle is a sliding plunger that
moves in a linear direction
One revolution of the thimble moves
the spindle 0.025” or 1 graduation on
the sleeve
The spindle carries the second of the
measuring surfaces that contacts the
object being measured
The Frame and Anvil
The frame is the main support member
for all other parts of the micrometer
The anvil is located in the far end of the
frame and provides the fixed measuring
surface
The frame will have the size and type of
micrometer marked on it
They are usually made from cast of iron
The lock
May be of a lever type or a roll type
Locks the spindle to the sleeve so that
readings can be taken easily
Allows you to capture the reading of the
scales
The Vernier scales
This is a new scale that is located on
the sleeve near the frame
Allows you to read 0.0001 inches or
0.001 mm
The scale is a subdivision of the thimble
scale and breaks 0.001” down by 10
=0.0001 or, on the metric scale 0.01mm
divided by 10 =0.001 mm
Standard micrometer
Vernier scale
lock
anvil
spindle
thimble
ratchet
sleeve
Decimal
readout
frame
scale