Rotary Saw and Chain Saw

By
John Mittendorf
– April 5, 2010Posted in: FD Training
When opening the compartment doors of a typical fire engine in the United States, a wide variety of tools and equipment will normally be observed. These various tools and equipment...

When opening the compartment doors of a typical fire engine in the United States, a wide variety of tools and equipment will normally be observed. These various tools and equipment are generally based on a combination of tradition, NFPA standards, district needs, and the always popular “its always been there.” Several standard tools and equipment that readily come to mind are the pike pole, pick-head axe, ground ladder, and rotary saw. However, a tool that is becoming more popular due to its effectiveness is the chain saw. As the rotary saw and chain saw are similar, they can also be diametrically different in their application. For my next two articles, we’ll review the advantages and disadvantages and review several operational considerations of the two saws. First, we’ll review the rotary saw.

ROTARY SAW
The venerable rotary saw is an excellent multi-purpose tool that is versatile and effective in a variety of applications, depending on the blade that is utilized. Cutting thick or heavy roof composition normally found on older roofs, metal deck roofs, lightweight concrete roofs, and metal in forcible entry applications readily come to mind. However, several noteworthy disadvantages should also be considered when using this power saw as follows:

  • The blade can continue to spin after the throttle is released or the saw is shut-off.
  • A rotary saw can exhibit a gyroscopic effect that is caused by the spinning blade. Depending on the cutting angle, this can 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 5-inches deep, with 4-inches being the norm.
  • In some applications, a rotary saw can be heavy and difficult to operate in precarious conditions. As an example, while operating from a roof ladder, try to reach out with this saw to cut a ventilation opening.

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

  • First, always wear the appropriate safety equipment when operating the saw.
  • Due to the versatile nature of the saw from its 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. Keep in mind that multi-use blades will cut virtually anything and eliminate changing blades (depending on the material to be cut), and eliminate the shattering of composite blades that is commonly occuring with modern composite blades.
    • Most rotary saws will allow the blade to be mounted in the inboard or outboard position and is easily accomplished by rotating or reversing the bar that holds the blade (be sure to check the operators manual for your saw). As an example, if a rotary saw is used for ventilation operations, mount the blade in the inboard position as this will minimize the gyroscopic effect by centering the blade with the saw. However, if the saw will be used for forcible entry operations, mount the blade in the outboard position. Although this will maximize the gyroscopic effect, it will allow the blade to be inserted 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 will hold the saw off of 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 to be cut 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 backwards. Therefore, use a safety person to watch the overall operation and the area behind the person using the saw.

Check back next time as we review the chain saw.

John Mittendorf

About John Mittendorf

John Mittendorf was a 30 year veteran of the Los Angeles City Fire Department and held the rank of Battalion Chief until his retirement in 1993. He 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, UCLA, and the British Fire Academy in England. He has acted in an advisory capacity for five college fire science advisory boards and is the author of numerous fireground articles for magazines in the United States and Europe. He is the author of the books Ventilation Methods and Techniques, Truck Company Operations, and Facing the Promotional Interview. He currently lectures in the United States and the United Kingdom on strategy and tactics, truck company operations, fireground operations, ventilation operations, and the complete fire officer. He is a member of the editorial advisory board of Fire Engineering magazine.