C spanners, also known as adjustable hook spanners (or wrench) or hook & pin wrenches, are high-quality hand tools designed for tightening and loosening retaining rings. These specialist adjustable hook spanners incorporate steel roll pins that allow the jaws to adjust to the correct size of the ring.
Slotted retaining rings, unlike nuts, have a smooth, rounded circumference, making it difficult to adequately grip the ring with a standard spanner. To overcome this, C spanners have a small cylindrical pin at the crest of the head that slots into a hole in a retaining ring. This essentially locks the spanner into the ring so that the two remain joined once torque is applied.
C-shape spanners get their name from the shape of the hook, which, when open, looks like a large letter 'C'. While this is the typical shape of a C spanner, some manufacturers make hook spanners in different shapes and designs for added torque. Additionally, not all C spanners are adjustable.
Because of the amount of torque needed to loosen rings, C spanners need to be made of strong materials. Commonly, they are made from alloyed steel, like chrome vanadium steel, or other tough metals. If they are made from a lighter material, such as plastic, they might break or crack once torque is applied.
Our range of C spanners covers versatile and easy-to-use tools and includes leading brands such as Cooper Tools, Facom, GearWrench, and RS PRO.
Finding the right C spanner for a given job or to stock in your tool chest comes down to a few key deciding factors. Because C spanners have such a specific use case, you will likely know what sizes you will need ahead of time so you can buy the right size.
The first deciding factor for which type C spanner to buy would be if your job requires using multiple rings in different sizes. If it does, it might be worthwhile to invest in an adjustable C spanner. This guarantees you have the right size spanner for each ring without having to carry multiple tools at a time.
Still, with adjustable hook spanner wrenches, you still need to determine what length handle you need. Simple physics informs us that the longer the length of the spanner handle, the less force you need to apply to create equal torque. This means that it takes less effort to tighten or loosen a ring if the C spanner has a longer handle. While it may seem logical to buy the longest adjustable C spanner, the space you have to work with may not be able to accommodate a long tool.
If you don't need an adjustable head, then you just need to factor in the length of the handle and the style of head you prefer. While most hook spanners have the traditional 'C' shape, others are shaped differently. A different shape both affects the amount of torque you can apply and the angle at which you work on the ring. There may be a scenario where a C-shaped hook spanner doesn't fit but a different head shape does.
C Spanners are a specialty tool with very specific use cases. One of the most common industries to use them is the automotive industry. This is because cars, motorcycles, and other vehicles make heavy use of slotted retaining rings.
Ultimately, C spanners are most appropriate when the job entails tightening or loosening a slotted retaining ring or similar nut or bolt.