What's The Difference Between GO And NO-GO Thread Gages?

If the products you manufacture contain threaded shafts or holes, then you need to make quality checks to ensure that these spaces are the right size for their fittings. If a hole is too small or too big to take its bolt, for example, then you have a problem.

Thread gages are a simple solution here. These devices screw or plug into the hole or shaft to help you check its size to make sure it meets the standards you set for the product. Often, gages use different sizing techniques, known as GO and NO-GO, to do this. What's the difference?

What Does a GO Thread Gage Do?

If you need to check that a fixing will fit exactly into a hole or shaft, then a GO thread gage does this job for you. You insert this kind of gage into the space to see how it fits.

If your size and dimensions are exactly right, then the gage will fit in the hole precisely. It will screw in relatively easily. It will fill the space from both a width and length perspective without feeling too loose or too tight.

If your space isn't the right size, the gage won't work. If the hole is too big, the device won't stick in place; it might move around or not fill the space completely. If the space is too small, the gage won't go in easily. You might have to use too much force to insert it or it might not go in at all.

What Does a NO-GO Thread Gage Do?

While a GO thread gage is supposed to fit into its size of hole, a NO-GO gage gives you a different way of checking dimensions. This kind of gage shouldn't fit into the hole or shaft.  If it does, then you have a problem.

So, you might be able to fit the NO-GO gage into the beginning of the space. It might even make a couple of turns. At this point, however, the gage shouldn't go any further. This helps you check slightly larger spaces that you might not easily notice on a GO gage.

If a NO-GO gage goes in too much or all the way, then you know that your space is too big. It doesn't meet your specifications.

While some gages have a GO end and a NO-GO end, others work separately. To find out which kind of device best suits your products, ask thread gage suppliers like WESTport for advice.