Lessons for the Shop and Job site

Though each test trial produced slightly different results, the top and bottom performers remained relatively constant while those in the middle shifted around. The most telling result was the confirmation that testing impact torque is still very difficult, regardless of the technology employed. Still, using the high-tech test equipment taught me some things about impact drivers that I didn’t know before — and that will change the way I use them on the job. Here’s some advice based on what I learned.

Add mass. Up to a point, driving a heavier mass will increase inertia, allowing an impact driver to deliver more force. I discovered this when, partway through testing, I switched from a standard impact socket to a heavier (twice as heavy) deep impact socket. All of a sudden some of the impact drivers were delivering more than twice the force output they had been before. But there are limits. I later added socket extensions but found that too much extra weight counteracted the action and didn’t add force.

The use of a heavier socket proved more helpful for hard-joint driving (tightening bolts), so it couldn’t hurt to try a heavier socket if you’re having trouble driving a long lag with a too-light nut driver bit.

Keep it loose. There will be a certain amount of play in the connections between the tool’s bit holder, the socket adapter, the socket, and the head of a lag bolt. This is good because a few times every second the connections will slam tight in unison and the force output will spike. At least that’s what happened during force testing; the readings were higher if I kept a loose grip on the tool and didn’t push too hard.

Use impact-rated accessories. Not only are impact-rated accessories less likely to break — they transfer more of the power to the fastener being driven. I know this because during the first test every tool showed the same torque reading. It turned out the wimpy adapter I was using was flexing at a certain level of torque, beyond which it could not deliver force. Switching to sturdy impact-rated adapters solved that problem, making it possible to differentiate between the most and least powerful tools. I’m sure some impact energy was still being lost to the adapters. After all, every adapter I used eventually broke after enduring a certain amount of strain.

Use the right tool. If you are driving bolts and lags routinely, you will be better-served by a cordless impact wrench with a square drive end for sockets rather than an impact driver that fits only 1/4-inch hex shank bits. Besides (usually) being rated as more powerful than their related driver, wrenches take the weak link out of the equation. When you need to drive plain old screws, there are bit-holder attachments that fit the 1/2-inch square end of an impact wrench, and even sockets that standard screwdriver bits snap into.

The Brushless Difference

How much of these tools’ performance can be attributed to their high-efficiency brushless motors? Good question. When their runtime and driving speed are compared with those of the mostly conventional-motor impact drivers in the previous tool test, you can see a noticeable increase across the board. But for the longest-running models, new beefed-up batteries deserve at least some of the credit. It’s certainly no coincidence that the two tools that did best in the runtime test are the only ones with 4.0- and 4.2-amp-hour (Ah) 18-volt batteries. The tools with 3.0-Ah packs were at a distinct runtime disadvantage.

The author ran each tool for three seconds while it was connected to a digital torque tester cabled to a meter.

The author ran each tool for three seconds while it was connected to a digital torque tester cabled to a meter.

Credit: Michael Springer

The meter converted average peak impulse into dynamic torque and displayed that value on a digital readout.

The meter converted average peak impulse into dynamic torque and displayed that value on a digital readout.

Credit: Michael Springer

Tools were operated for three seconds while connected to a bolt tension calibrator. Results were displayed on a gauge in pounds of force, which were converted into inch-pounds with a digital torque wrench.

Tools were operated for three seconds while connected to a bolt tension calibrator. Results were displayed on a gauge in pounds of force, which were converted into inch-pounds with a digital torque wrench.

Credit: Michael Springer


Bottom Line

Launch Slideshow

Most impact drivers have a single LED light  usually above the trigger, but sometimes on the base. A couple of models have an array of three or four lights around the nose.
  • A brushless tool motor is controlled by a microprocessor, which makes it possible to add features like variable speed/power ranges, automatic downshifting, and advanced protection and diagnostic functions.

    http://www.toolsofthetrade.net/Images/tmpB7F2%2Etmp_tcm80-1827632.jpg

    A brushless tool motor is controlled by a microprocessor, which makes it possible to add features like variable speed/power ranges, automatic downshifting, and advanced protection and diagnostic functions.

    600

    Michael Springer

    A brushless tool motor is controlled by a microprocessor, which makes it possible to add features like variable speed/power ranges, automatic downshifting, and advanced protection and diagnostic functions.

  • Each impact driver was tested with the brands highest-capacity battery. For five of the tools, this meant using 3.0-Ah packs like the DeWalt battery shown here. Hiltis top battery is rated at 3.3 Ah, Milwaukees at 4.0 Ah, and Panasonics at 4.2 Ah.

    http://www.toolsofthetrade.net/Images/tmpBDC0%2Etmp_tcm80-1827643.jpg

    Each impact driver was tested with the brands highest-capacity battery. For five of the tools, this meant using 3.0-Ah packs like the DeWalt battery shown here. Hiltis top battery is rated at 3.3 Ah, Milwaukees at 4.0 Ah, and Panasonics at 4.2 Ah.

    600

    Michael Springer

    Each impact driver was tested with the brand’s highest-capacity battery. For five of the tools, this meant using 3.0-Ah packs like the DeWalt battery shown here. Hilti’s top battery is rated at 3.3 Ah, Milwaukee’s at 4.0 Ah, and Panasonic’s at 4.2 Ah.

  • Most impact drivers have a single LED light  usually above the trigger, but sometimes on the base. A couple of models have an array of three or four lights around the nose.

    http://www.toolsofthetrade.net/Images/tmpC5FE%2Etmp_tcm80-1827653.jpg

    Most impact drivers have a single LED light usually above the trigger, but sometimes on the base. A couple of models have an array of three or four lights around the nose.

    600

    Michael Springer

    Most impact drivers have a single LED light — usually above the trigger, but sometimes on the base. A couple of models have an array of three or four lights around the nose.

For me, grip comfort, headlight brightness, and control-panel options take a back seat to the speed and power of driving. Creature comforts can add to the enjoyment of using a tool, but all else being relatively equal, I’m going for the cordless tool with guts. Especially since these models can be dialed down when less power is needed.

Runtime may be a consideration for heavy users, but since impacts are fuel-efficient by their very nature, the full-size batteries in this class probably pack a full day’s work for average uses. With a two-battery kit, you should never be without power if your tool lasts at least half a day on a battery. In fact, to avoid lugging around any more bulk and weight than is necessary, a high-efficiency 18-volt brushless impact driver with a new 2.0-Ah compact battery is probably the most evolved choice for the average user, but compact batteries aren’t currently an option for all brands.

My leading picks come right off the top of the speed and torque tables, with the Milwaukee and both Panasonic tools leading the pack. The Milwaukee in particular dominated the charts, distinguishing itself as the strongest and fastest tool in the class. These three tools also took the top four spots in the runtime results.

Hilti, DeWalt, and the Makita LXDT01 occupy the second tier, followed by the Makita LXDT06. After the Hitachi is the single-speed no-frills Makita LXDT08, which seemed out of place in a test of otherwise sophisticated tools.

 
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    Credit: Michael Springer

DeWalt DCF895L2
Battery: 18 volts; 3.0 Ah
Approx. charging time (supplied charger and battery): 60 minutes
Rpm: 0–950; 0–1,900; 0–2,850
Max IPM: 3,300
Head length (by ToTT): 51/4 inches
Weight (by ToTT): 3.69 pounds
Country of origin (tool/battery/charger): China/Japan/Thailand
Includes: Two batteries, charger, case, belt clip, spare bit holder
Web price: $340
Features: Three speed ranges; ranges controlled by slide switch; push-button release chuck with one-handed bit loading; three LED lights; lights are trigger-actuated with 20-second delay; fuel gauge on battery; charger also charges 12V Max batteries; case is extremely compact
Comments: Solid second-tier tool; unique recessed bit holder in nose; bit is released by pressing a button above trigger; triple LED around nose provides effective lighting; only tool with onboard bit storage; also available in compact battery kit

 
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    Credit: Michael Springer

Hilti SID18-A
Battery: 21.6 volts; 3.3 Ah
Approx. charging time (supplied charger and battery): 50 minutes
Rpm: 0–1,000; 0–1,500; 0–2,500
Max IPM: 3,450
Head length (by ToTT): 515/16 inches
Weight (by ToTT): 3.96 pounds
Country of origin (tool/battery/charger): China/China/China
Includes: Two batteries, charger, soft bag, belt clip
Web price: $415
Features: Three speed ranges; ranges controlled by push-button switch; one-handed bit loading; four LED lights; lights are trigger-actuated with 10-second delay; fuel gauge on battery; base of battery is rubberized; kit is also available with plastic case
Comments: Capable and strong second-tier tool; large 21.6-volt battery makes this the heaviest model tested; four LEDs surrounding nose provide shadow-free illumination; also available in compact battery kit

 
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    Credit: Michael Springer

Hitachi WH18DBDL
Battery: 18 volts; 3.0 Ah
Approx. charging time (supplied charger and battery): 45 minutes
Rpm: 0–900; 0–1,400; 0–2,000; 0–2,600
Max IPM: 3,200
Head length (by ToTT): 61/8 inches
Weight (by ToTT): 3.75 pounds
Country of origin (tool/battery/charger): China/China/China
Includes: Two batteries, charger, case, belt clip
Web price: $265
Features: Four speed ranges; ranges controlled by push-button switch; one LED light; light is manually operated, stays lit 15 minutes; battery gauge on tool; two trigger modes — continuous (standard) and limited (three or four impacts only); optical trigger switch said to be more durable than standard mechanical switch; case is very compact
Comments: Bulky; flexed and vibrated under heavy driving loads; lagged behind in speed and runtime testing; small uncomfortable trigger; unique limited-impact mode proved extremely handy for carefully driving screws that last little bit

 
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    Credit: Michael Springer

Makita LXDT01
Battery: 18 volts; 3.0 Ah
Approx. charging time (supplied charger and battery): 30 minutes
Rpm: 0–1,300; 0–2,000; 0–2,600
Max IPM: 3,400
Head length (by ToTT): 51/2 inches
Weight (by ToTT): 3.46 pounds
Country of origin (tool/battery/charger): China/Japan/China
Includes: Two batteries, 30-minute charger, case, belt clip
Web price: $295
Features: Three speed ranges; ranges controlled by push-button switch; one-handed bit loading; one LED light with 10-second delay; light can be disabled; warning lights for low battery, overheating, and locked motor; nose of tool glows in the dark; case is very compact
Comments: Solid second-tier tool; felt strong and eager in use and placed quite well in many of the power tests; could benefit from a battery fuel gauge

 
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    Credit: Michael Springer

Makita LXDT06
Battery: 18 volts; 3.0 Ah
Approx. charging time (supplied charger and battery): 30 minutes
Rpm: 1,400; 2,300; 2,800; T-mode = 2,800
Max IPM: 3,400
Head length (by ToTT): 51/8 inches
Weight (by ToTT): 3.42 pounds
Country of origin (tool/battery/charger): Japan/Japan & China/China
Includes: Two batteries, 30-minute charger, case, belt clip
Web price: $360
Features: Three speed ranges and Quick-Shift mode that automatically downshifts under load; ranges and special mode controlled by push-button switch; one-handed bit loading; one LED light with 10-second delay; light can be disabled; battery gauge on tool; overheat warning light; nose of tool glows in the dark; case is very compact
Comments: Most compact tool in test; in unique T-mode for self-tapping (TEK) screws, driver runs in full speed until screw gets a bite; as load increases tool finishes drive at medium speed to avoid stripping the threads; only Makita model with a battery fuel gauge

 
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    Credit: Michael Springer

Makita LXDT08
Battery: 18 volts; 3.0 Ah
Approx. charging time (supplied charger and battery): 30 minutes
Rpm: 0–2,500
Max IPM: 3,200
Head length (by ToTT): 53/4 inches
Weight (by ToTT): 3.56 pounds
Country of origin (tool/battery/charger): China/Japan & China/China
Includes: Two batteries, 30-minute charger, case, belt clip
Web price: $300
Features: One speed range; one LED light; light is trigger-actuated with no delay; case is very compact
Comments: Bare-bones model; performed near bottom in most tests

 
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    Credit: Michael Springer

Milwaukee 2653-22
Battery: 18 volts; 4.0 Ah
Approx. charging time (supplied charger and battery): 60 minutes
Rpm: 0–850; 0–2,100; 0–2,900
Max IPM: 3,600
Head length (by ToTT): 51/2 inches
Weight (by ToTT): 3.74 pounds
Country of origin (tool/battery/charger): China/Korea & China/China
Includes: Two batteries, charger, case, belt clip
Web price: $300
Features: Three speed ranges; ranges controlled by push-button switch; one-handed bit loading; one LED light; light is trigger-actuated with 10-second delay; fuel gauge on battery; base of battery is rubberized; charger accepts M18 and M12 batteries; case is very compact
Comments: The strongest, fastest tool — topped all others in speed and torque testing; second-best runtime; came with new high-capacity 4.0-Ah battery; also available in compact battery kit

 
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    Credit: Michael Springer

Panasonic EY7550LR2S
Battery: 18 volts; 3.3 Ah
Approx. charging time (supplied charger and battery): 65 minutes
Rpm: 0–1,000; 0–1,400; 0–2,500
Max IPM: 3,300
Head length (by ToTT): 55/8 inches
Weight (by ToTT): 3.48 pounds
Country of origin (tool/battery/charger): China/Japan/China
Includes: Two batteries, charger, case, belt clip
Web price: $360
Features: Three speed ranges; ranges controlled by push-button switch; one LED light on base; light is manually operated, stays lit five minutes; warning lights for low battery and overheating of motor or battery; tool is IP56-rated for resistance to moisture and dust; case is overly bulky
Comments: A top-tier performer along with its brand mate; felt very strong in use and consistently placed high in speed and power tests; could benefit from a battery fuel gauge

 
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    Credit: Michael Springer

Panasonic EY75A1
Battery: 18 or 14.4 volts; 4.2 Ah
Approx. charging time (supplied charger and battery): 80 minutes
Rpm: 0–1,000; 0–1,400; 0–2,500
Max IPM: 3,000
Head length (by TOTT): 55/8 inches
Weight (by ToTT): 3.60 pounds (18v); 3.33 pounds (14.4v)
Country of origin (tool/battery/charger): China/Japan/China
Includes: two 18-volt batteries, charger, case, belt clip
Web price: $400
Features: Three speed ranges; ranges controlled by push-button switch; one LED light on base; light is manually operated; warning lights for low battery, overheating of motor or battery, and locked motor; tool is IP56-rated for resistance to moisture and dust; case is overly bulky
Comments: A unique flexible-fuel tool that runs on 14.4-volt or 18-volt batteries; a top-tier performer; equally powerful with either battery; with 4.2-Ah 18-volt battery, had best runtime in the test; the lightest tool tested when fitted with 14.4-volt pack; could benefit from a battery fuel gauge

—Michael Springer is the former executive editor of Tools of the Trade.