Understanding the various categories of thread gauges!

Understanding thread gauges takes time. It comes with knowledge, practice and experience. When I was new to metrology and was inspecting threading parts, I constantly used to get confused with its terminologies. With so many thread gauges existing in the market, I took a fair amount of time before I could actually figure out the … Continue reading “Understanding the various categories of thread gauges!”

Understanding thread gauges takes time. It comes with knowledge, practice and experience. When I was new to metrology and was inspecting threading parts, I constantly used to get confused with its terminologies. With so many thread gauges existing in the market, I took a fair amount of time before I could actually figure out the significance of various gauge types.

Today I share my experience just to make things simpler for all those new to using these gauges. So pay close attention to what I put down.

Clearing out the basics of threading operations:

But before laying down various types of gauges along with their different uses, there is something which I should clear out first.

When you carry out a threading operation, numerous factors are involved. They include the main and minor diameter of the thread, its flank angle and its pitch diameter (TPI or pitch). Explaining this last aspect better, TPI means threads per inch which is applicable in case of SAE or Standard American Equivalent threads and Pitch for metric threads.

How I saw it was, a normal GO/NO-GO gauge was used to inspect the thread from the pitch diameter. But for special cases where the major diameter in case of a screw or a minor diameter in case of a nut proved critical, specific GO/NO-GO gauges were employed. These gauges were used along with the other thread gauges to examine the threaded portion.

Hopefully this part is clear. Now it’s time to introduce you to some thread gauge terminologies. Keep on reading…

The various genres of thread gauges:

I’ll start off with thread plug gauges –

This is a gage which can be used to check the acceptance of the internally created threads. These thread plug gauges are created to check the accurateness of the TPI or pitch. The Go gauge goes through the complete length of the nut but without much rotation for acceptance of the thread part. As for the No-Go gage, it enters the nut being examined at both its ends, but it shouldn’t go beyond a couple of turns.

The 2nd type of thread gage is alterable thread ring gage –

These are your ring shaped gages having a split and an adjustable locking screw. When functioning with these gages, you have to use a setting plug to set up these tools.

The 3rd kind is solid thread gages –

These are also your normal screw gages but with them, you can check the acceptance of the external thread portion. They also make use of the TPI or pitch to check the accurateness of the thread point. You will find them in separate pieces of GO and NO-GO gages. The GO ring gage has to pass completely through the screw without force, in other words, easily. Whereas the No-Go gage can get into the screw for not more than a couple of rotations!

The 4th kind includes thread caliper gages –

While working on external thread parts, I also found that apart from using thread ring gages, thread caliper gages can also be put to usage. These thread gauges ensure fast inspection. They simply slide into the thread part with the help of gravity with Go-rollers.

An important tip – If your job requirement needs mass production involving fast inspection of screws, then thread caliper gages are your option to go for. But these are not as effective as compared to a thread ring gage and they also have less wear resistance.

You can also use a spare thread ring gage for additional inspection just in case.

So there you have it, the different types of thread gauges for your different thread part measurements. When purchasing, I would suggest you to choose a company with good market repute and also who guarantees quality and genuine-ness in each of the offerings. They’ve all for now, until next time. And here’s wishing all the best for your threading operations. Cheerio!