Rotary Saw vs. Chain Saw, Part 1


By John W. Mittendorf

The venerable rotary saw is an excellent multipurpose tool that is versatile and effective for a variety of applications such as cutting thick or heavy roof composition normally found on older roofs, metal deck roofs, lightweight concrete roofs, and metal in forcible entry, depending on the blade you use.

However, the rotary saw also has several noteworthy disadvantages.

  • The blade can continue to spin after the throttle is released or the saw is shut off.
  • A gyroscopic effect caused by the spinning blade can, depending on the cutting angle, cause the saw to be unwieldy.
  • Depending on the size of the saw and blade, the depth of cut is normally limited to 3.5 to five inches deep, with four inches being the norm.
  • In some applications, a rotary saw can be heavy and difficult to operate-for example, while operating from a roof ladder and try to reach out with this saw to cut a ventilation opening.

To obtain the maximum benefit from a rotary saw, observe the following:

  • Always wear the appropriate safety equipment when operating the saw.
  • Because of the saw’s versatile nature and the ability to use a masonry, wood, or metal cutting blade, determine the primary use for the saw and equip it appropriately as follows:
    • If the primary use is ventilation in wood roofs, mount a carbide-tipped wood-cutting blade. Conversely, if the primary use is forcible entry, mount a metal-cutting blade.
    • With most rotary saws, you can mount the blade in the inboard or outboard position easily by rotating or reversing the bar that holds the blade (be sure to check the operator’s manual for your saw). For example, if you use a rotary saw for ventilation operations, mount the blade in the inboard position to center the blade with the saw and minimize the gyroscopic effect. However, if you use the saw for forcible entry operations, mount the blade in the outboard position. Although this will maximize the gyroscopic effect, you can insert the blade into areas with minimal space constraints (i.e., sliding the blade under a tempered glass door to cut a pivoting bolt on the lock at the bottom of the door).
  • While cutting a surface, most firefighters hold the saw off the surface. This can place unnecessary weight on the back muscles and enhance “binding” the blade in the cut. To minimize this problem, place the saw on the surface you are cutting and pull the saw into the cut. This will allow the saw to glide on the blade guard and lower portion of the carrying handle, allowing the surface to support the weight of the saw and center the blade in the cut.
  • When cutting a surface with a rotary 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.

PART 2 >>>>

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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