Shear Attachments

MAY/JUNE 2007

BY THEODORE FISCHER 

For nearly 30 years, mobile shear attachments have done a spectacular job of cutting huge pieces of scrap down to size. Though they originally marketed them as tools for lowering labor costs and boosting safety, shear manufacturers now emphasize how much speed, versatility, and raw power their products bring to scrap processing operations.
   A dozen or so manufacturers in the United States, Canada, and Europe currently dominate the mobile shear market, their products performing similar functions in distinctly different ways. What they all have in common, though, is the goal to continuously improve their products: to manufacture faster, stronger, safer shears that experience less downtime and demand less maintenance. So what have they done lately to advance those goals?

A need for speed
When it comes to mobile shear attachments, bigger isn’t always better—but faster is. Most manufacturers now use speed valves or regeneration valves to shorten the path the hydraulic fluid takes through the equipment, shortening cycle times. One manufacturer uses both dual-moving jaws and a shock-free circuitry design with fewer flow paths for greater speed. “The new technology provides fast, smooth, and silent operation, with unnoticeable transition shift from speed to power, and it reduces the possibility of additional heat generation to the tool or the machine’s hydraulic system,” he says. The shear’s direct port system eliminates hose failures inherent in other speed valve designs, he adds.
   The integrated speed valves on another company’s shear attachments can reduce cycle times for large base machines to less than 8 seconds, the firm states. A third manufacturer’s new regeneration speed valve “allows the shear, when it’s not under any load, to go much faster,” the vendor says. “When it’s actually performing the work, it shifts out of speed mode and goes into power mode, and then you have the force you get just from a standard cylinder.” Another company touts its spool-type speed valve, which offers faster cycle times and prevents contamination of the hydraulic system, it says.

Pumping up power
Cutting strength is a selling point for many shear attachments, and each manufacturer has its own approach to boosting power. One bolsters efficiency by using larger cylinders and an increased cylinder stroke, which increase power without any need for a larger base unit. It offers a shear for a 70,000-pound material handler that provides the cutting power usually found in shears mounted on 100,000-pound handlers; its shear for a 100,000-pound base machine cuts like it’s attached to a 125,000-pound machine, the firm says.
   Another manufacturer’s patented hydraulic system “links the tool’s cylinders to a pair of levers, delivering an ever-increasing power gain with every inch of jaw closure, rather than the less effective power curve found in other designs,” resulting in 99-percent mechanical-hydraulic power efficiency, according to a company representative. The design provides a surplus of power throughout the jaw closure while keeping the cylinder away from the material, he says, allowing the shear to effortlessly cut through materials thick and thin and eliminating the choking and jamming problems associated with tools that lose power during closure.
   A different company’s dual-guide slide puck system supports the attachment’s upper jaw on both sides, which boosts cutting efficiency by keeping the jaws aligned throughout the cutting
cycle and enhances cutting force up to 15 percent, it says. The system reportedly also extends blade life and increases pivot and jaw component life.

Bringing jaws to life
Manufacturers have modified their shear jaw designs to increase their safety and functionality. One sculpted jaw, cast from proprietary high-alloy steel components, eliminates external tool cylinders and gives operators complete visibility, regardless of tool and jaw positioning, its manufacturer states. “The cylinder remains completely enclosed within the tool’s main body at all times, keeping
it protected from material damage and eliminating all possibility of visual obstruction to the machine’s operator caused by external hydraulic cylinders and bulky shrouds or guards,” the vendor says.
   Other changes make shears more efficient by increasing blade contact with material. The upper jaw of one manufacturer’s rebar cutting shear now has staggered blades that can hold and process the rebar as it moves into the lower jaw, a design that requires less power than attachments that feed material into an apex, the company states. The 18-inch-wide upper jaw and offset lower jaw maximize the power efficiency of the excavator’s bucket cylinder by cutting material first on one side and then on the other side.
   Versatility is another trend in jaw design. One manufacturer offers patented jaw-set technology that Includes a shear and a cracker/crusher jaw set, neither of which ever requires hub adjustments or shaft removal—the machine’s operator can switch jaws in the field in as little as 15 minutes, the company states.
   In another line of shear attachments that has both pulverizer and shear jaw sets, each jaw retains its own pivot group, so changes involve just hydraulically releasing one jaw and using the company’s quick-coupler technology to attach the other one. Only the cylinder pins need to be removed manually. The quick-changeover capability prevents bearing contamination and reduces wear due to exposure to the elements during lengthy change-outs, the company states.
   In a slightly different approach, a European manufacturer recently introduced a multipurpose attachment that shears and pulverizes concrete. The unit’s patented undulated knives also grip and cut rebar.
 
Durable goods
Manufacturers are trying to reduce downtime by building shears with stronger materials and better protection for hydraulics. To enhance the durability of the shear body as well as its wear parts, one manufacturer has introduced a proprietary-grade high-alloy steel throughout its tool design. “Unlike steel plate designs, this proprietary material is more solid, dense, and uniform, eliminating the possibility of material separation due to internal stress risers or weldment failures commonly found in tools designed from steel plate,” the vendor says.
   To minimize hydraulic and other failures, this company focused on better protecting vulnerable parts. “The [new shear series] maximizes cylinder life and performance by using a short-stroke, heavy-duty, trunion-mounted cylinder that works inline, rather than a long-stroke, base-mounted cylinder that works under continual side-loading stress,” the vendor says. The fully enclosed cylinder’s rod and barrel are never exposed to damage caused by material contact. A sealed shaft keeps the hydraulics free from contamination that other shears might experience during shaft removal and hub adjustments.

Building better blades
Blades are literally the cutting edge of shear attachments, and they’re the one part that inevitably will wear with use. The proliferation of bolt-on wear parts in recent years represents the great leap forward for shear attachment maintenance, one vendor says. “Shears used to have bolt-on blades for cutting, but they always had a weld-on piercing tip on the movable jaw that took the brunt of all the beating a shear gets,” he says. “What everyone’s been working on over the last few years is how to make that tip replaceable, so you don’t have to cut it off and weld on a new one.”
   He estimates that the process of removing an old tip, welding on a new one, and then making sure it’s aligned properly takes from two to four hours. With his company’s bolt-on tip, he says, “now you can change your piercing tips in 20 minutes and get back to work.”
   In other blade developments, one company’s fully interchangeable blade system uses four identical cutting blades, so users can rotate blades front-to-back and top-to-bottom, much like
rotating the tires of a car. This shear also has a dual-guide blade system and a piercing tip operators can shim to accommodate whatever scrap is on hand—with higher degrees of tolerance for lighter material, to reduce the risk of jams, and lower tolerances for heavier material. In a different company’s design, threaded bolt holes and slotted shims make knife changing quick and easy, and a bolt-on wear plate protects the upper jaw.
   To reduce blade maintenance and enhance performance, another manufacturer has introduced an automated blade lubrication system. The company claims that the system doubles blade life and halves welding time on affected jaw areas, cutting downtime by at least two weeks a year. It also reduces the welding that shortens component life and diminishes shock loading throughout the shear and excavator.
   “Our scrap customers say they actually get more power out of the shear
because they’re not getting the friction between the blades as much, so they’re definitely seeing notable improvements in cutting efficiencies,” says the vendor, who estimates that the reduced friction even boosts power by up to 8 percent.
   No matter how well the shear attachments are constructed, one vendor blames erroneous maintenance practices for a lot of unnecessary downtime. “Shears wear as they cut metal—there’s metal-to-metal contact at all times during this operation. A lot of people are using the wrong kind of welding rods to build them up, and that causes the steel to crack,” he says. Specifically, he says, welding with high-wear-resistant rods tends to generate stress cracks. “No matter who builds that shear, if users weld on it with the wrong kind of welding rod, it’s going to crack wide open.”

From shear to eternity
Mobile shears have come a long way in 30 years, but they still have room for improvement. “One challenge is that you’ve got to change your product to match up to the [base machines], which are always changing,” a vendor says. “Number two is the power-to-weight ratio—maximizing power but keeping the weight at a reasonable number.”
   Along those lines, one manufacturer expects to see shears doing more with less. “Equipment will get smaller and lighter and still maintain the force it has today,” he says. “Then users will be able to put a stronger shear on a smaller carrier. If the shear was smaller or lighter, you could put it on a smaller excavator—and that saves money, transportation, a whole bunch of things.”
  

Reducing maintenance time and costs are other continuing concerns. “Customers are always beating us up over that,” a vendor says. “They don’t want downtime.”
   And these manufacturers struggle with steel—both the alloys used for blades and the metals the blades must cut. “We’re always looking for a better mousetrap for our raw material,” one shear expert says. “We literally go to the ends of the earth to find the best stuff to make our product.” Another one agrees: “Until somebody invents some new alloys for blades, so you can use higher hydraulic powers to cut more, I think they’re doing about [all] they can do no matter who builds it.”
   One vendor dreams of giving his scrap processor customers a product that shears the hitherto unshearable. “Hardened steel like slag, thick plate—they’re always looking for a way to cut that material,” he says. “It would be nice if you could use a shear for that, but that stuff is just too hard with the technologies we have today.”
   Looking even further ahead, one manufacturer fantasizes about presenting customers with a shear that minimizes—or even eliminates—the human component. “They’d love to have a product that could go up to a pile of scrap—there’s no operator involved—and by the end of the day that pile of scrap is cut up into the sections they want. It’s completely automated,” he says. “Scrapyards and demolition contractors are hurting just like everybody else. Getting good labor at a reasonable rate is a constant challenge. Safety is a huge issue. So the more you can remove the direct labor component from a scrapyard, the better.”

Shear Excellence
If you’re in the market for a new shear attachment, take a look at the products offered by the following vendors.
A-Ward Attachments Ltd., 201/697-7301, www.a-ward.co.nz

Allied-Gator Inc., 800/624-2867, www.alliedgator.com

Atlas Copco Construction Tools Inc., 413/746-0020, www.atlascopco.com

Caterpillar Inc., 309/675-1409, www.cat.com

Genesis Attachments, 715/395-5252, www.genesisattachments.com

Iron Ax Inc., 478/252-0022, www.ironax.com

NPK Construction Equipment, 440/232-7900, www.npkce.com

Pemberton Inc., 800/393-6688, www.pembertoninc.com  

Sierra International Machinery LLC, 661/327-7073, www.sierraintl.com

Stanley LaBounty, 218/834-2123, www.stanley-hydraulic-tools.com

Tramac Corp., 973/770-4457, www.muscle-mate.com

Vibra-Ram Inc.,780/452-0606, www.vibra-raminc.com

Theodore Fischer is a writer based in Silver Spring, Md.