Jaw plates do the hard work in a jaw crusher, and they rarely wear evenly from top to bottom. Most plates are designed to be reversed, which gives operators a simple way to get more tonnes out of each set before replacement.
In this article, we explain how jaw plates wear, the signs that show it is time to turn them and how to measure wear accurately. We also share practical tips for getting the most from every flip.
How Jaw Plates Wear
Material enters the top of the chamber as large rock and is crushed progressively smaller as it moves towards the discharge opening. The lower section of the plates does the most work, taking repeated impact and grinding as the rock is reduced to its final size. As a result, the bottom third of a jaw plate typically wears much faster than the top.
This uneven wear is exactly why many jaw plates are made symmetrical. Turning the plate end to end moves the lightly worn top section to the bottom, where it takes over the heavy work. The worn section moves to the feed end, where wear is slower and the main job is gripping larger rock.
The type of rock also plays a role. Hard, abrasive material such as granite, quartzite or basalt wears plates faster than softer limestone or recycled concrete. Plates in abrasive applications need checking more often, since the window for turning them at the right point can close quickly.
Signs It Is Time to Turn Them
The right time to turn your jaw plates is usually when the teeth at the bottom have worn to around half of their original height. At this stage, the lower section still has enough profile to grip material once it moves to the top of the chamber. Waiting much longer can leave the flipped section too flat to hold rock at the feed end, which reduces nip and allows material to slip.
Changes in production often give early clues. If the product is getting coarser or more flaky, or if the closed-side setting needs frequent adjustment to hold the same size, the lower section is likely wearing down. A noticeable drop in throughput or a rise in power draw can point to the same thing.
A visual check helps too. Worn plates often develop a hollow or belly shape near the discharge while the upper teeth still look sharp. When that difference between top and bottom becomes clear, flipping jaw plates at that point makes the best use of the remaining material.
Measuring Wear the Right Way
Appearance alone can be misleading, so regular measurement is worth the effort. Measure tooth height at several points along the plate, particularly across the lower third, and compare the readings with the dimensions of a new plate. Many operators use a simple template or profile gauge to keep this quick and consistent.
Record each measurement alongside the tonnes processed since installation. Over a few change-outs, this builds a reliable picture of how fast plates wear in your application. Knowing when to rotate jaw dies then becomes a matter of planning rather than guesswork.
Measure the fixed and movable plates separately, as they rarely wear at exactly the same rate. Depending on the setup and feed material, one may see more rubbing action while the other takes more direct impact. Tracking each plate individually lets you turn or replace them on their own schedule.
Getting the Most From Each Flip
Turning a plate is also an ideal time to inspect the parts around it. Check the cheek plates, wedges and bolts for wear, and replace any that are no longer holding the jaw plates firmly. A plate that sits loosely will wear faster and less evenly.
Clean the seating surfaces on the frame and pitman before refitting the plate. A build-up of fines or old backing material can stop the plate from seating properly, which leads to movement during operation. Tighten the fasteners to the recommended settings and recheck them after a short period of running.
Once the plates are back in place, reset the closed-side setting to suit the required product size. Good feeding practices, such as keeping the chamber choke fed, spread wear evenly across the new working section and help the plates reach their full potential.
In Conclusion
Jaw plates wear fastest at the bottom of the chamber, so turning them when the lower teeth reach roughly half their original height gives the best return from each set. Watching for changes in product size and throughput, measuring wear regularly and inspecting surrounding parts during each flip will help you get maximum life from your plates.
When it is time for replacements, our team at Caldas Engineering supplies premium manganese jaw plates and wear parts for leading crusher brands, backed by warehouses in Johannesburg, KwaZulu-Natal and Kimberley. We also supply new crushers for operations looking to expand. Contact us today for a free quote and let our experts help you keep your crushers running efficiently.
Rui Caldas, founder of Caldas Engineering, specializes in the supply of quality wear and mechanical parts for the crushing and screening industry. With a commitment to customer engagement and innovative solutions, his expertise ensures minimal operational downtime, supported by a skilled in-house design team focused on continuous improvement.