A micrometer screw gauge is made up of a “U” shaped metallic structure that is attached to a hollow cylindrical tube on one end of the tool. Inside the hollow tube is the uniformly threaded nut. Into this nut, a long stud with a plane face is fitted. Also, on the other end of the “U” shaped frame, at the exact opposite side of this nut, a smaller stud with the plane face is attached. The faces of the two studs are situated exactly parallel to each other.
The “U” shaped metallic structure is referred to as the frame of a micrometer screw gauge. While the smaller stud is referred to as an anvil, the longer stud is referred to as the spindle. The spindle moves as and when the head is moved whereas the anvil is the fixed part. The object is meant to be measured in place between the anvil and the spindle. The frame carries both the barrel and the anvil. The barrel or sleeve is a part that connects the frame to the non-movable cylindrical tube of the micrometer screw gauge with a scale inscribed over it. This scale is referred to as the main scale of the device.
The heart of the micrometer screw gauge is the screw that is located inside of the barrel. The screw helps to convert small dimensions of samples into measurable distances using the scale. The device also carries the head or thimble which is the end of the cylindrical tube that can be turned to move and adjust the spindle. The thimble is the part on which the secondary scale is displayed.
At the end of the tube is the ratchet which is a limiting device that applies pressure by slipping at a predetermined torque. As a result, it prevents the spindle from moving further. While there are vast varieties of micrometers for specific applications, some consist of locking devices. This locking device holds the scale at a specific measurement to prevent any kind of error while taking measurements.
Hence the main parts of a micrometer screw gauge as explained earlier include the following:
- “U” shape frame
- Anvil
- Spindle
- Sleeve
- Thimble
- Ratchet
- Screw
- Lock