Rotary Saw vs. Chain Saw, Part 2


By John W. Mittendorf

The chain saw can simplify numerous operations. However, compared with the rotary saw, the chain saw is not as versatile and is limited to primarily cutting operations in wood. Yet, the recent focus (and need) for aggressive ventilation operations on the modern fireground has placed a great deal of emphasis on timely and safe horizontal and vertical ventilation operations, specifically vertical ventilation. When considering vertical ventilation operations on roofs (which are normally wood), the power to weight ratio, reach, and lighter weight of a chain saw can be significant advantages in terms of operational efficiency and safety.

However, consider some noteworthy disadvantages when using the power saw:

  • Chain saws were not originally designed for fire department operations. An ill-equipped saw in concert with an engine displacement that is not sufficient for the specific needs of a district will not be a favorite tool of fireground personnel.
  • Depending on the length of the bar, there can be a considerable amount of exposed cutting teeth. Therefore, it is imperative that personnel moving a running chain saw move with safety (operator and other personnel) as a prime consideration.
  • If a chain saw is not operated correctly, it can “kick back.”
  • Similar to rotary saws, a chain saw can be a powerful and safe tool if operated within appropriate safety guidelines. However, if personnel have not received adequate training, the saw should be left on the apparatus.

To obtain the maximum benefit from a chain saw, consider the following:

  • Always wear the appropriate safety equipment when operating the saw.
  • As necessary, practice with the saw to develop a “feel” for it and its capabilities (which can be impressive).
  • When cutting with a chain saw, the operator must back up or walk backward. Therefore, use a safety person to watch the overall operation and the area behind the person using the saw.
  • Some chain saws can be purchased or retrofitted with a protective cover (i.e., guard/depth gauge) over the bar and chain. This device will protect personnel from the cutting teeth and can be adjusted to allow the saw operator to monitor the depth of cut.
  • A “properly” equipped chain saw for fire department operations has the following items:

    • Minimum 68 to 72 cc or four-cubic-inch engine. This will provide adequate power for wood roofs with light and heavy coverings. Remember that municipalities located at above-average elevations (i.e., 5,000 to 7,000 feet) with heavy roof coverings may require a larger engine. For example, a chain saw operated at 7,000 feet will have a 30 percent power loss.
      NOTE: Newer saws are more tolerant to elevation changes due to EPA regulations requiring cleaner burning engines. Additionally, it will not be possible to adjust these carburetors for maximum performance.
    • 18- to 20-inch bar. This will allow good “reach” with the saw (important when working from roof ladders) and allow the saw operator to stand fairly erect while cutting. This minimizes weight on the back muscles and maximizes the distance between the surface being cut and face of the saw operator.
    • Sprocket tip bar. A “hard nose bar” can cause unnecessary friction that will result in a slower chain speed and elevated chain temperatures (this causes the chain to stretch and droop after cutting). A bar with a sprocket on the end of it that turns on a roller bearing will result in a faster chain speed and chain temperatures that can be reduced by 170 degrees. This minimizes chain stretch and the chain melting the tar in roof coverings during cutting operations. To further reduce the weight of a chain saw and increase the hardness of a bar (longevity), purchase titanium bars.
      NOTE: Regardless of the type of bar you use, do not use standard motor oils (i.e., 30 weight) or oil mixed with various types of thinners. This will minimize lubrication at the tip of the bar and dramatically accelerate wear. Always use bar oil designed for your chain saw.
    • Muffler guard. A simple piece of aluminum or thin steel mounted to the front of the muffler will dramatically reduce maintenance by keeping the saw cleaner during cutting operations and keep debris from adhering to a hot muffler.
      NOTE: You can apply a nonstick cooking spray to a clean bar, muffler guard, and engine to further reduce maintenance. This will minimize oils and debris sticking to the treated surface.
    • Large air cleaner. This will provide an increased filtering area in smoky conditions.
    • Carbide tipped chain. These are vastly superior to standard chains for roof ventilation operations. I strongly recommend you “try before you buy.” A new type of carbide chain referred to as the “bullet chain” has excellent cutting speed and longevity and will easily cut 18 gauge metal with minimal detrimental effects to the cutters. For maximum effectiveness, this chain requires a saw of at least four cubic inches and chain pitch of .404-inch .063 gauge. A chain saw with a torque curve near the maximum rpm of the engine is also recommended for best results.
    • Accessible tool for adjusting or replacing the chain. Buy a short piece of 1/4- or 3/8-inch fuel line and tape it to the side of the saw hand guard. Insert the chain tension-replacement tool into the fuel line. The tool will now be with the saw when you need it, not on the apparatus in the street.
    • Carrying strap. This allows personnel to carry a chain saw, leaving both hands free to climb ladders, etc.
    • Gasoline today is significantly different from the gasoline of yesterday and has numerous additives that can be detrimental to two-stroke engines (chain or rotary saws). Therefore, ensure your gasoline is fresh (change it at least every 30 days) in your supply cans and in your power equipment. A good gas additive such as an octane booster will also keep your gasoline fresher longer but will not solve the additive problem. One solution to the additive problem (depending on your area and the additives used) is to run a 50/50 mixture of pump gasoline and racing gasoline.

    John W. Mittendorf joined the Los Angeles City (CA) Fire Department (LAFD) in 1963, rising to the rank of captain II, task force commander. In 1981, he was promoted to battalion chief and in the year following became the commander of the In-Service Training Section. In 1993, he retired from LAFD after 30 years of service. Mittendorf has been a member of the National Fire Protection Research Foundation on Engineered Lightweight Construction Technical Advisory Committee. He has provided training programs for the National Fire Academy in Emmitsburg, Maryland; the University of California at Los Angeles; and the British Fire Academy at Morton-in-Marsh, England. He is a member of the editorial advisory board of Fire Engineering and author of the book Truck Company Operations (Fire Engineering, 1998).

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