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New Cutting Solutions for Tough-to-Cut Glass Mat Wall Sheathing

Over the last several years, the construction industry has witnessed tremendous advances in residential and commercial building materials, specifically new materials designed to combat moisture-related problems. Driving the need for this innovation is what some call the next asbestos: black mold.


Headlines about “sick building syndrome” and families suffering from alleged mold-related illnesses have become an increasingly common occurrence across the United States during the last few years. The cause of this problem is varied but mainly attributable to two things: advances in construction methods and materials that have led to more energy-efficient, air-tight homes and buildings that don’t breathe or vent like those built 20-plus years ago; and too much moisture penetrating into the wall cavity by some means, thereby allowing potential mold growth.


Once moisture has entered into the wall cavity and combines with stagnant air and the paper facing found on traditional drywall sheathing, the condition is ripe for mold growth. The problem isn’t the gypsum but rather the paper, which is an organic material—a food source for mold.


Many wall sheathing product manufacturers have addressed this issue by offering new sheathing components, featuring coated glass mats on both the front and back of the gypsum instead of traditional paper facings, as well as fiberglass fibers interwoven in the gypsum. These new glass mat coatings repel moisture better, and since they’re paperless, they are not a food source for mold.


These new moisture-resistant glass coated sheathings and underlayments greatly reduce mold growth on interior or exterior walls. The problem, however, is that these materials are harder to cut for the installers than paper-faced drywall. The cutting edge of standard carbon utility blades do not last nearly as long when cutting the new materials as they do when used on standard paper-backed drywall. In addition, the blades shatter more often because of the increased lateral force needed to drive them through the materials, creating significant productivity issues (more blade changes, less time cutting) and safety concerns.


Professional drywall installers and remodelers are learning that yesterday’s carbon steel cutting tools just aren’t durable enough to maintain their sharpness for extended periods of time when up against glass-backed drywall. Because users are forced to change the blades more often, productivity is decreased and costs are increased. A solution for cutting these new materials is needed.


Various manufacturers of cutting tools have begun including features in their products that address the challenges associated with cutting today’s coated glass mat sheathing drywall and underlayments. Installers should look for the following features in their cutting tools:



  • Strong, yet flexible bi-metal blades.
  • A technology that allows blades to stay sharp longer.
  • A nose that resists spreading.
  • A quick-change blade feature.
  • A comfortable ergonomic grip.



A cutting tool for these new harder materials needs to be strong, but it also needs to be flexible. The latest utility blades feature bi-metal construction, which addresses this issue well. Bi-metal is made with two pieces of steel welded together, providing a flexible steel backing that allows the blade to bend without breaking. Some manufacturers have been making reciprocating saw blades from bi-metal for decades, as it is tough enough to withstand vibration and tough cutting while allowing for flexibility. Recently, this technology has become available in utility blades as well. Shatter-resistance in a utility blade becomes especially important for safety reasons when cutting harder materials.


Professionals who routinely use utility blades on the job are picking up on the benefits of bi-metal. Billy Smith, an apprentice instructor at the Carpenters Training Center for the United Brotherhood of Carpenters in Rockford, Ill., recently used bi-metal utility blades to cut some vinyl flooring transition strips—a material he has cut using only standard carbon steel blades in the past. “These strips are a pretty hard material,” Smith said. “Standard carbon steel blades work good on the strips right at first, but have a tendency to dull after a few cuts. Bi-metal blades are not only flexible, but also last four to five times longer. That’s great because there’s less downtime; you don’t have to change blades as often.”


A blade designed to maximize its edge hardness would dull less frequently in even the hardest materials. The best means available today for providing such increased blade edge hardness without having to make the blade from a material so hard as to render it brittle and inflexible is through the use of advanced second-generation coatings such as titanium nitride (TiN). Coatings add additional harness and wear resistance. They also provide a lower coefficient of friction, allowing the blade to cut more smoothly through the material.


For years, utility-knife users have reported problems with their knives spreading when applying downward pressure to cut standard drywall. These same users can expect even more spreading when cutting these harder materials because of increased lateral force needed to drive the blade through them and then drag downward. Today’s new utility knives are being designed to lessen spreading; the latest includes a one-piece, titanium-coated stainless steel nose for longer tool life.


Having to disassemble a knife in order to change the blade is frustrating because it takes time—and time is money. Today’s harder drywall and underlayments demand a quick blade-change mechanism, and several manufacturers have refined this tool feature to dramatically lessen the time needed to change blades. What’s more, the latest tools include magnets on the inside of the knife that will allow users to use both sides of the blade, no matter how mangled it may be.


And cutting harder materials means that users are going to have to grip the knife more securely. The best instrument for cutting these materials should have a comfortable, ergonomic grip. Some of the latest tools have softer, rubber grips; some are shaped to easily fit in a user’s hand; and many of the buttons to retract or tighten the blades are easier to reach and require no tools to operate.


As the concern over toxic mold continues to grow, the use of coated glass mat moisture-resistant drywall and underlayments will expand tenfold in the years to come. Installers need to equip themselves with the latest technology in cutting tools and blades. Bi-metal blades and innovative utility knife handles offer installers the best combination of performance, safety and durability.


About the Author

Sean Boyle is the senior product manager for cutting tools at LENOX®, a leader manufacturer of premium hand tools, power tool accessories, and band saw blades.


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