Which British Thread Gage Do You Need?

Thread gages allow you to check the accuracy of threads in nuts, bolts, and other parts needed in machinery. British thread gages are commonly used in most countries, and while the United States tends to use other threads in general, you can find British thread types here, too. It helps to have thread gages at the ready should one of these British threads exist on machinery you've received. You need to know what gage to use when, however. British threads come in a number of varieties, and you'll need different gages for each.

The Specific Type of Threads

First, there are the specific types of threads. These include British Standard Whitworth, British Association, and others. Each is used on different types of equipment and in different systems, although there is overlap. Some of these types are older and not used that much anymore, but you will still want a gage to measure them should you have older machinery that you're using.

The Specific Shape of the Threads

The British threads have a couple of different shapes you'll encounter. In one, called parallel, the threads are all of the same width, height, and angle; they're all identical, as you see on most other bolts and screws. The other type is called tapered, and as the name suggests, these threads taper off in one direction. The shapes of the threads affect how tightly the threads on one part can lock together with the threads on a second part.

Internal or External Threads

Then there are internal and external threads. External threads are threads on the outside of the item that has the threads. A screw has external threads, for example. Internal threads are those inside a part, such as the threads in the inner ring of a bolt. The gages used to measure internal and external threads differ, with external-thread gages looking like wheels with the thread-measuring gage in the center. Internal-thread gages have the thread-measuring part at the end of a rod; the gage looks like a bolt. Some of these gages have different sets of threads at each end.

Even if you don't work with British threads at all right now, it helps to have the gages handy. With international manufacturing and tight supply lines, you could find yourself faced with British hardware that needs special gages for proper measurement. When you know you can reach over and grab an appropriate gage, your work won't have to stop. 

For more information, contact a local company that has British thread gages for sale