Page 7 - 9-phy-1 Measurements
P. 7
1.3 Measure the thickness of a metal strip or a
wire by using a Screw Gauge.
Date ________________
Screw Gauge is a device used to measure length as small as 1/100th of
millimeter (0.01 mm).
Screw Gauge has two scales
(i) Main Scale
(ii) Circular Scale or Thimble scale
Anvil Spindle Lock Main scale Thimble Ratchet
Datum line
Frame Fig. 1.3.1
Pitch of Screw Gauge
The distance moved on the main scale by giving one rotation to the circular
scale is called pitch. Usually it is 0.5 mm for 50 divisions on circular scale.
Least Count Pitch
Least Count = Number of divisionson the circularscale
0.5mm
LC = 50 = 0.01 mm
Zero Error
10 10 5
5 5 0
00 00 0 45
45 45 40
40
(b) (c )
(a) Positive zero error Negative zero error
No zero error
Fig. 1.3.2
7
wire by using a Screw Gauge.
Date ________________
Screw Gauge is a device used to measure length as small as 1/100th of
millimeter (0.01 mm).
Screw Gauge has two scales
(i) Main Scale
(ii) Circular Scale or Thimble scale
Anvil Spindle Lock Main scale Thimble Ratchet
Datum line
Frame Fig. 1.3.1
Pitch of Screw Gauge
The distance moved on the main scale by giving one rotation to the circular
scale is called pitch. Usually it is 0.5 mm for 50 divisions on circular scale.
Least Count Pitch
Least Count = Number of divisionson the circularscale
0.5mm
LC = 50 = 0.01 mm
Zero Error
10 10 5
5 5 0
00 00 0 45
45 45 40
40
(b) (c )
(a) Positive zero error Negative zero error
No zero error
Fig. 1.3.2
7
