Become familiar with the design, features and operation of 24-volt cordless reciprocating saws for rescue.
Subject: Cordless Reciprocating Saws, Part 5
Topic: 24-Volt Cordless Reciprocating Saws
Objective: Become familiar with the design, featurs and operation of 24-volt cordless reciprocating saws for rescue.
Task: Compare the advantages of 24-volt cordless reciprocating saws for rescue operations.
DeWalt Tool Co. introduced a brand-new 24-volt cordless reciprocating saw and 24-volt system in November 1999, the DW008K. After working with this saw and evaluating it under realistic fire service conditions, it is apparent that this saw represents the future of cordless saws for the fire service. This new saw meets and exceeds the capabilities of all other existing 18-volt units.
24-Volt Reciprocating Saw Features
The nine-pound saw operates at two speeds: 0-2,400 strokes per minute on one setting or 0-2,900 at the second position. Each stroke moves the blade a distance of 1 1/8 inches. The moment the saw operator releases the trigger, an "instant stop" feature activates an electronic brake to halt all blade movement.
This 24-volt saw has been "ruggedized" for fire service use. In a UL drop test, the saw functioned properly after a one-meter (39-inch) fall onto a hard surface. A 110-volt corded unit presents an electric shock hazard if it were to be used in a wet atmosphere. Although not recommended, the 24-volt cordless saw can be used in rain or under other wet conditions. As long as it is cordless, it has no electrocution possibility for the operator. A wet saw can be dried out with a hair dryer after use.
The 24-volt saw comes equipped with a three-position adjustable shoe that extends the guide shoe from its retracted position a distance of 1 1/2 inches. This lets the operator instantly concentrate the cutting action on different teeth along the saw blade.
Originally, reciprocating saws were provided with a separate chuck key to release the saw blade. DeWalt changed all that when it introduced a lever-action keyless blade clamp on all of its corded and cordless saws. The 24-volt DW008K incorporates this blade clamp release lever, allowing for blade changes in as little as three seconds.
It made sense to me that this is a feature to be well received by firefighters, since there would no longer be a separate chuck key to lose at an emergency scene. What I failed to realize was how a keyless blade clamp would also streamline operations during a rescue.
A "blade change" test was conducted comparing a corded saw with a manual chuck key to the DeWalt lever action release. On the first reciprocating saw, the chuck key was tethered to the power cord by a rubber retainer strap. Using the allen wrench key, our saw operator attempted to change the saw blade as quickly as possible. The operator required 25 seconds to release the chuck, remove the old blade, insert a new blade and tighten the clamp, making the saw ready for service.
With the DeWalt blade clamp release lever, the operator was able to remove the old blade and have a new saw blade ready for use in just three seconds. With this system, the operator averaged six complete blade changes in the same 25 seconds that it took a saw operator to change one blade using the chuck key attached by a rubber strap.
Battery & Charger Unit
The 24-volt battery is larger in size than the DeWalt 18 volt unit because there are now 20 cells inside, compared to the 15 found in an 18-volt battery. The three-pound battery uses a new slide rail system to attach to the handle of the saw. A single button at the rear of the handle allows the battery to be released.
The low-profile 24-volt charger unit incorporates a red LED light to indicate charging status. The unit also has a patented Tune-Up mode that, when activated, equalizes and balances all individual cells in the battery to their peak capacity. This option takes from three to six hours to complete, compared to a standard recharge time of one hour. If used every 10th battery charge, the Tune-Up mode will increase battery life by 20% and increase battery performance.