Subject:	Cordless Reciprocating Saws, Part 5
	Topic:	24-Volt Cordless Reciprocating Saws
	Objective:	Become familiar with the design, features 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 an 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 most revolutionary innovation to date that ensures fire sevice acceptance of cordless tool technology is the 24-volt AC-DC converter shown on the DEWALT Tool Co.'s DW008 cordless reciprocating saw.

The 24-volt battery uses a new slide-rail mounting system and a large quick-release button.

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. 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 for 1-˝ 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 seconds.

It made sense to me that his 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 the 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 read 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.

Endurance Test: 24-Volt Reciprocating Saw

The reciprocating action of the new DW008 is shown in the cutaway view. As the large yoke oscillates at the bottom, the socket at the top drives the blade shaft back and forth.

The 24-volt battery is larger in size that the orgional 18-volt battery. Its power output averaged six minutes of constant, aggressive vehicle rescue cutting.

The 24-volt saw gave consistently food performance under all tests conducted. The "no load" test time, where the saw was allowed to run without cutting anything until the motor action stopped, averaged between 17 and 18 minutes.

A series of 24-volt battery endurance times measured during aggressive, constant cutting tests of vehicle A-pillars ranged from five minutes, 18 seconds to six minutes, 39 seconds. During one test, I cut the A-pillar seven times, sliced through the B-pillar 12 times, and still had enough power to cut the steering wheel ring three times. During a test where the battery ran for six minutes, 28 seconds, I cut completely through the driver's side rocker channel 20 times.
5:59
6:28 (rocker, 20 cuts)
6:07
6:39 (one column, two door hinges, seven C-pillars)
5:18 (seven A-pillar, 12 B-pillar, three steering wheel ring cuts)
Immediately after use, the batteries are warm to the touch. They require a cool-down period before the charger unit will begin to recharge them. Recharge time is about one hour.

AC/DC Converter

In the fire service, we routinely attack structure fires with on-board water in the apparatus booster tank. This initial fast attack is then supported by a sustained water supply from a hydrant line or tanker operation. DEWALT has taken this age-old fire service tradition and adapted it to the field of cordless saw technology with the introduction of a 24-volt AC/DC converter accessory. The AC/DC converter concept will revolutionize the application of cordless tool technology for the fire service.

To use this amazing converter, the saw operator simply removes the 24-volt battery and slides the AC/DC converter into the handle. With its electric power cord plugged into a 110-volt power source, the 24-volt saw runs indefinitely.

This accessory makes any complaints or concerns about battery endurance moot. Start with the cordless off a single 24-volt battery. With the "initial attack" cutting underway, a partner had more than five minutes to start a generator, plug in an electrical cord and advance the line with the AC/DC converter to the saw operator. The operator stops long enough to remove the cordless battery and slide in the converter. In seconds, the cordless saw now has unlimited run time.

If you do not yet have a reciprocating saw in your fire and rescue tool inventory, then this is the saw kit to buy. If you have an 18-volt system, make it your backup and upgrade to the state-of-the-art 24-volt technology with the AC/DC converter. It's the best of both worlds.

Do you want to see this artical in its orginial, printed format? Cordless Reciprocating Saws, Part 5

Note: Acrobat plug-in is required for viewing. To get the FREE Adobe Acrobat plug-in click here.