What is Screw Gauge?
Screw Gauge is a mechanical tool that is used to measure the diameter or radius or thickness of a thin metal sheet with utmost precision. There are two scales known as Pitch Scale which is generally the main scale and also is engraved on the barrel with upright lines.
Another one is the Circular scale which is engraved horizontally on the thimble. Pitch range determines the range in millimeter (mm) traveled by the spindle per transformation. One change by the round range amounts to the fifty percent of a millimeter of displacement of the screw is called a micrometer screw gauge.
The readings of screw gauge are more precise and accurate as compared to Vernier Calipers.
Parts of Screw Gauge
It includes a U-shaped steel structure F with a fixed stud A.
- The right moveable R (called Ratchet) is a cylinder kind whose other end is called the spindle.
- A static straight scale or the main scale (usually in mm) is noted on a cylindrical tube.
- The second scale (moveable) is called a circular scale or a capped range (with 50 or 100 parts) which is made use of a cap called thimble ‘T’ fitted over a cylindrical tube.
- The round scale is made as though one total turning of the cap relocate horizontally by 1 mm on the main scale if circular scale cap relocates horizontally by 1 mm on the major scale if circular scale division is 100 and also 0.5 mm in the main scale if the circular scale division is 50.
Working of Screw Gauge
The primary step is to locate the zero error of the screw gauge.
To find the zero error, shut the void between the pin and the stud of the screw gauge by rotating the ratchet in the clockwise direction. If zero of circular range coincides with the index line, then the zero error will certainly be zero.
Zero error will be positive if zero of circular scale is behind the index line. In this instance, multiply the number of divisions of the circular scale that has actually not crossed the index line with the least count of screw gauge to fine zero error.
Zero error will certainly be negative if zero of circular scale has actually crossed the index line. In this situation, increase the number of divisions of the circular scale that has crossed the index line with the least count of screw scale to find the zero error.
How to Take Reading
The size of a provided object can be found as follows:
- Shut the space in between the spindle and the stud of the screw gauge by turning the ratchet in the clockwise direction.
- Note the main scale along with circular scale reading to locate zero error as well as for this reason no modification of the screw gauge.
- Open the void in between stud and pin of the screw scale by turning the ratchet in the anti-clockwise direction. Place the object in the void. Turn the ratchet to ensure that the object is pressed carefully between the studs and also the spindle.
- Note main scale as well as circular scale readings to find the size of the object.
- Apply zero error to get the correct diameter of the object.
Least Count of Screw Gauge
The least count of a screw gauge can also be found by the formula:
The least count of screw gauges is 0.01mm or 0.001cm.