Cordless Reciprocating Saws - Part 3

Understand Reciprocating Saw Bi-Metal Blade Design and Function.Subject:  Cordless Reciprocationg Saws, Part 3Topic:  Selection and Use of Bi-Metal Blades for Reciprocating Saws at Vehicle Rescue IncidentsObjective:  Understand Reciprocating Saw...

For every quantity of reciprocating saw blades that a fire department stocks on its rescue vehicles, the majority of them should be eight or nine inches in length. We should always have available two or three blades that are six inches in length and another two or three that are extra-length 12-inch blades.

If I could only have 12 saw blades with me on a rescue call, I’d want eight of them to be eight-inch, 10/14-tpi blades. I’d want two more to be 12-inch, 6-tpi blades and the final two to be 6-inch 10/14-tpi blades. This selection would be the basis of my saw blade starter kit.

No Blade Lubrication During Vehicle Rescue!

Cutting through certain hardened metals with a reciprocating saw can produce small sparks. This is due to the overheating of the metal being cut. Blade manufacturers instruct industrial saw users to lubricate saw blades with cutting oil when using a reciprocating saw. The manufacturers' engineers explain that lubrication at the point of cutting makes for an easier operation and provides a longer blade life.

Firefighters, seeing these recommendations, have for years lubricated reciprocating saw blades at vehicle rescue incidents. When we used actual cutting oils, we found that the friction of the saw blade as it cuts produced a smoke that smelled like something was burning. This was not good for a conscious patient to smell while trapped inside a vehicle. So the "cure-all" solution was introduced: soapy water. It doesn’t smoke, it’s cheap and it appears to work.

Field research conducted by this author has determined that lubrication of a reciprocating saw blade during vehicle rescue incidents does not noticeably improve cutting speed or the efficiency of the cutting action. In addition, applying soapy water from a squeeze bottle ties up a rescuer that could be better put to work doing something productive. Without lubrication, you do get additional heat around the teeth, which softens them. Blades will have to be changed more often, but with the new saws having a keyless chuck, a blade change takes less then three seconds to complete.

Under fire-rescue applications, I recommend NOT lubricating the blade of a reciprocating saw. We are not interested in saving money by prolonging the life of the blade as the owner of a machine shop would be. We’ll throw our used blades away when we return to quarters and will come to the next extrication call with a fresh blade installed in the saw. Don’t waste your time or your personnel lubing a blade!

Lubrication is recommended, however, for the reciprocating saw itself. Tools used under real-world rescue applications can quickly accumulate foreign materials inside the working components of the saw especially at the blade clamp area. Periodic cleaning, inspection and lubrication of the saw at an authorized service center will increase the reliability of the tool and prolong its useful life span.

Proper Cutting Procedures

Here are some general guidelines to consider when working with a reciprocating saw at fire-rescue incidents:

· Hold the saw firmly with both hands, but only by the insulated gripping surfaces, when performing a cutting operation. Unintentional contact with a "live" energy source, such as a wire of the vehicle’s electrical system, can energize the exposed metal parts of the entire tool. This will cause shock to the saw operator if your hands are incorrectly placed on the bare metal of the tool.

· If you have a variable-speed reciprocating saw, select the proper speed for the material being cut. As a general rule, with harder metals such as cast door hinges or Nader pins, a slower saw speed will be more effective. A lower speed setting, approximately 1,500 strokes per minute, is good for most metal cutting. Increasing the motor speed to full does not get a significant improvement in cutting speed. Slowing the blade speed down increases blade life and does not reduce overall cutting time.

· With a variable-speed feature on your saw’s trigger, "feather" the speed to give you the best performance. If you have to work only at the high-speed setting on your saw, adjust your grip to a moderate pressure on the material being cut. Relaxing the pressure slightly will actually allow the blade to cut faster and to last through the entire cutting action.