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Maintenance/Management: Getting the right bite

May 28, 2009 |

Anybody who has ever struggled to push a dull saw blade through a thick piece of wood knows how much more muscle power it takes when your tools aren’t sharp.

The same principle holds true for excavator and wheel loader bucket teeth. The wrong tooth or a blunt tooth forces you to burn more fuel and robs you of many buckets over the course of a day. When you have the power of a diesel engine and robust hydraulics providing the muscle for the digging you may not notice it much, but over time the wrong tooth hurts your productivity and profitability.

In their quest to continually improve the performance of machines, manufacturers are developing new tooth systems that penetrate well, stay sharper longer and offer tooth-to-adapter locking systems in which the retaining pins are installed from the top rather than the side, making them easier to change and more secure. Although the goals of these new tooth systems are similar, the design details vary considerably. So it behooves you to learn specifically how teeth affect productivity and how each of these new systems may meet your needs.

The impact of teeth
“If it doesn’t take as much force to push a bucket into the pile, then the loader or excavator doesn’t use as much fuel,” says Bob Klobnak, senior product consultant, Caterpillar marketing and product support division, ground engaging tools. “Those two things are directly related. It varies a lot depending on the material and in easy digging it may not make much difference, but in harder digging our customers have verified productivity and wear life increases with teeth that have a lower profile for easier penetration.”

In assessing different teeth you want to consider the balance between wear life and penetration, says Kirk Yoresen, marketing communications manager, engineered products, Esco. “You can make a tooth that will wear for a long time, but it may not be easy to push through the material. Some customers may have a material that is difficult to load and opt for penetration over wear life. Then another customer digging in the same material, but with a different machine or some other variable, may find wear life more important than penetration.” Wear life is often the most important trait in mines and big quarries when downtime is limited, he says.

New locking systems
With the advent of top-locking tooth systems, however, manufacturers were able to partially break free from this penetration vs. wear-life dilemma. Before the top-locking systems, most teeth were secured to the adapters with a thick steel pin hammered into the side of the tooth and adapter. Since this pin and the holes it went through were the weakest point on the tooth/ adapter assembly, manufacturers had to beef up the metal around it – creating a tall, thick tooth with steeply angled top and bottom surfaces. These teeth were strong, but massive, more like molars than incisors.

With the top-locking mechanisms, the need for all the metal bulk supporting the side pins went away. Tooth profiles slimmed down considerably, the top and bottom angles flattened out and the wear metal was pushed to the front, creating a more knife-like blade with better penetration and improved wear life.

The basic principles of these top-locking systems are the same, but most manufacturers have a slightly different retaining pin system. Some are tapped in and tapped out, some can be pressed in by hand, others use pry bars or special tools. Some are held in place with spring-tensioned steel, others use compressible rubber or polyurethane retainers. The locking pins themselves take little of the load, so to take the stresses that used to be transmitted to the side pins, manufacturers have added more contact surface between the tooth and the adapters. Some of these are just large mating surfaces, others use a twist-on assembly that secures and provides more contact area.