Metric thread gauges are dimensional instruments which measure and verify the thread size, the pitch and other parameters. There exists a variety of thread gauging instruments and tools like a measuring wire, thread plug gauges, thread ring gauges and tri-roll comparators.
Fixed limits and appropriate variables for an application need to be selected depending on an internal and external type of thread. A better understanding of different types of gauges available has been given below.
What are the different types of thread gauges available?
Following are the different types of gauges available.
1. Plug gauge
It is a cylindrical shaped gauge which is used to check hole accuracy. You can use thread plug gauges for checking whether the diameter of the hole stays within the specified tolerance limits.
A Go plug gauge refers to the size of the lower limit of a hole while a No go plug gauge is associated with the higher limit of a hole. It needs to engage a hole to get it checked without the use of pressure, and it needs to be able to stand within the gap without falling.
2. Pin gauge
Whenever the holes which need to be checked are greater than 75 mm, as the automobile cylinders, using a pin gauge may be convenient. At the time of measurement, an indicator is kept lengthwise across the bore of the cylinder, and measurement is done. Such metric thread gauges are useful, especially when measuring slots or groove width.
3. Snap gauge
A snap gauge represents a U-shaped frame which has jaws that are used for checking shaft accuracy and male members. Snap gauge is used for checking if the shaft diameter is within specified tolerances.
A go snap gauge is used for checking the size of higher shaft limit while a no go snap gauge is used for the lower threshold of a shaft. Snap gauges are available in different designs. In some cases, both go and no go metric thread gauges are provided within a single jaw.
4. Ring gauge
A ring gauge is present in the form of a ring. You can use this for checking shaft members and male members. The go and no go members need to be separate or present in a single ring. The opening or hole gauge is usually larger than a no go gauge.
There are three types of ring gauges.
- Plain ring gauge
- Taper ring gauge
- Thread ring gauge
Measurement unit for thread plug gauges can be either metric or English. There are gauges which are configured for measuring both. The display on a gauge may be non-graduated which means that it does not have a display, analogue or digital. The choice of thread gauge depends on various factors. It is essential to make the right choice, as accuracy is of primary concern.