A cold planer can only perform as well as the cutter head system with which it is equipped. Using the best-designed planer available and fitted with a cutter system that is below par promises sub-par milling results. These sub-par milling results can often be traced back to uneven cutter-teeth wear or even missing (broken) teeth.
There are numerous cutting systems available on the market today, but they certainly are not all created equal. Which system is the best? That depends on which contractor you ask and under what set of conditions he operates the planer.
Key operations people with specialized contractor Donegal Construction Corp. have their view as to what cutter system works best for their operations. The system they have selected was based on its overall cost effectiveness, the productivity, its low maintenance costs and the teeth longevity. The company owns and operates 34 cold planers out of two operations locations. The corporate office and main operations are in Greensburg, Pa. The other location, in Burlington, N.C., is operated under the company name Delta Contracting Inc. A third company operation in Florida, Delta Milling Inc., was recently sold, including its 12 Roadtec planers.
The company serves in 14 states from New York to Georgia and going west to include Alabama, Tennessee, Kentucky and Ohio. Sixty percent of the milling services rendered is for road and paving contractors who hold DOT and local government paving contracts. The balance of the company’s contracts is carried out with contractors doing paving in the private sector.
Quantity over everything else
Donegal is one of the biggest, if not the biggest, pavement milling contractors east of the Mississippi River. The company employs 210 people. Once strictly an excavation and site contractor, it started the cold pavement planing business in 1989 with five profiling machines. This year, the company will add two more planers to the fleet, bringing the number to 36.
There are three makes of planers in the fleet, including Roadtec, Terex CMI and Wirtgen. Don Pfeifer, vice president, said all three have their attributes and have proven to be satisfactory. “We are very careful with what planer equipment we purchase because it represents a major investment for us.”
Likewise, the company has been careful in choosing the cutting system it uses on the planers. For the most part the company has been using the Kennametal Inc. cutting systems since 1989. The results experienced with the Kennametal products have been very satisfactory, according Pfeifer. Over the years, Kennametal has developed cutting systems with the objective of improving performance and cost effectiveness. The following is a short list that Pfeifer and Tim LaMantia, operations and maintenance manager, made up for evaluating a cutting system. They have taken the results of their evaluation very seriously, for the company replaces 11,000 worn cutter teeth each week. The economics factor clearly plays a significant role. While on the subject of cost effectiveness, Pfeifer said, “We have found the most economical cutting system to use is not based on the purchase price. Instead, we have correlated the cutting system’s overall life cost with the quantity of paving milled. That means we take into account the useable longevity of the system, the labor required to remove worn parts and replace them and the cutting performance. Of course, we also factor in the purchase cost.”
The labor entailed to replace a cutting system’s worn parts can vary considerably, depending on the cutting system design involved, according to LaMantia. For example, it was not too long ago that all of Donegal’s cutter assemblies were fastened to the cutter drum by welding them. LaMantia said it required an average of two hours of labor, each milling workday, just to remove worn or broken holders and weld on new ones. The on-location milling crew was responsible for making such repair procedures prior to the following day’s work.
By switching to Kennametal’s recently developed cutting systems, the KPF301 and KPF201, the worn or broken holders can be replaced in less than 30 minutes each day. That saves 7 1?2 hours of labor per week per planer. With more than 30 planers in operation at any given time, the labor saved is more than 225 hours per week.
The explanation for the drastic labor reduction is simple. Instead of laboriously having to remove the worn units and then welding on a new cutter assembly, the new cutting systems’ tooth-and-sleeve are easily extracted with a special Kennametal hand tool. Installing the new tooth-and-sleeve is easily achieved using a Kennametal hammer installation tool and an ordinary mid-weight hammer.
An important attribute of the KPF301 and KPF201 systems is the non-welded fastener/sleeve that acts as a bearing for the tooth shank so it can freely rotate. According to LaMantia, the sleeve’s bearing tolerances will gradually increase through wear from the tooth incrementally rotating. The progressive bearing wear of any cutting system will bring on a set of problems if it goes unchecked. For one, the cutter tooth will begin to wobble in the loose-tolerance bearing, thus widening the kerf (undesirable) and further causing the tooth to wear out prematurely.
Periodically, a cutter-head drum itself must be rebuilt to preserve the integrity of the overall milling performance. According to LaMantia, rebuilding a cutter-head drum of the older design cutting systems was necessary every year (after 1,100 to 1,200 milling operating hours). With the new-model cutting systems, the drums need not be rebuilt before 4,500 to 5,500 milling operating hours. This is not only a major savings in shop labor, but the yearly purchase costs associated with the new blocks is eliminated.
Less torque
Some cutting systems are fastened by the use of a screw. LaMantia said there are such systems on some of the company’s planers. He said the system is a good performer, but there is a major drawback to it, in his estimation. “The screws need to be retorqued every 200 operating hours, and on the average drum there are 150 such screws. The retorquing is time consuming because you first must clean out the asphalt. It is a day’s work to accomplish the retorquing and it must be done five to six times a year. When the cutting system must be replaced, we find it necessary to chase the screw threading for a good refit.”
When rebuilding a cutter head drum, LaMantia uses either the KPF301 or the KPF201 Pro-Fit block system depending on the spacing of the cut. Some cutters are spaced to make 5?8-in.-spaced cuts and others are spaced for making 5?16-in. fine-milling cuts. He said for the wider-spaced cuts the KPF301 system is preferable because of its outstanding weld life. However, the closer-spaced cutter heads are better served using the KPF201 because the block is slimmer, making it easier to service or replace despite its proximity to the neighboring blocks.
Doing what’s best
Where he can, Pfeifer specifies the Kennametal cutting systems on all newly purchased planers. Some manufacturers will not accommodate his wish. Nevertheless, he will buy their planer anyway if he thinks that particular model is best matched to certain planing project conditions. “If a manufacturer will not supply us with a Kennametal system with the planer, we will use their cutting system until it is time to rebuild it. At that time we will rebuild or replace the drum with the Kennametal system. It is not that the other system is not good, but it is not the best for us. Further, we prefer commonality of cutter parts for keeping stocked replacement parts at a minimum. We also are getting 3 to 5% better bit life with the KPF301 system,” he said.
Pfeifer is animated in not endorsing any given product. That said, he chooses the product he feels will be most cost effective for the company. There are three makes of planers in the fleet with a thumbs up, but only one make of cutter system. He is the first to say he is not loyal to any supplier but to his company. If the product is best suited for his company’s needs, he will continue to purchase it.
