Making an Impact

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This article is from Issue 8 of Woodcraft Magazine.

Impact drivers may look like small drills, but the similarity ends there. For decades, auto mechanics have enjoyed their high torque and unchallenged superiority in installing – and removing – fasteners with ease. As the same technology spreads to woodworkers, we’ll show you why you’ll want one in your shop.

By Tim Rinehart

Every now and then a new tool comes along that changes the way we perform some task. A tool that, after you first try it, any true tool junkie absolutely has to own one. The cordless impact driver is one of those tools. 

When I opened the case of the first sample to arrive I thought it looked like a wimpy little drill/driver wannabe. The compact little motor couldn’t have enough power and torque to do real work, so what could I do with this thing that any of my collection of drill/drivers won’t do? The answer turned out to be drive screws and lag bolts – lots of them – into everything I could find just for the fun of it.

Impact drivers use completely different mechanics than a standard drill/driver to deliver driving force. (See sidebar “How it works” on page 83) Under load, a spring is compressed which drives a hammer into an anvil to multiply torque. The extra torque is great, but there’s great side effect too: The millisecond space between impacts also lets screwdriver bits reseat themselves to full engagement with the screw head, virtually eliminating cam-out and stripped screws. I drove coated deck screws into hardwood until my arm gave out without a single cam-out or twist off. The same screws with my drill driver resulted in about one out of 10 either twisting off or stripping out the slots. When you consider how many screw heads you’ve stripped out with your drill/driver, this one advantage alone may be reason enough to justify owning one. 

Rule #1: These aren’t drill/drivers

Still, don’t throw away your drill/driver just yet. Impact drivers are in a completely different league for driving fasteners, but they’re lousy drills. Loud and slow, they do seem to handle smaller-diameter drill bits better than large ones. You can drill a hole in a pinch, but they weren’t really designed for drilling. This is why they have quick-change 1/4" hex chucks instead of standard three-jaw chucks. The drill/driver is still the best tool to carry up a ladder to drill a couple of holes and drive a few screws. But for driving fasteners into hard material, or driving a lot of screws or lag screws and bolts, the impact driver is so superior to a drill that you get spoiled quickly.

Originally, this was to be a short review of three new impact drivers’ features and specifications. But over the time I had the tools for testing, they have been the most-borrowed, hardest-to-get-back tools I have. All three were loaned for projects varying from assembling large wooden backyard swing sets, decks, docks, hanging drywall and building lawn furniture. We loaned one to some folks dismantling old bleachers at a local high school. We used them to remove rusted screws and bolts from a swimming pool frame, dropped them from ladders, generally used and abused them like we owned them (note to the manufacturers: Your returned samples may have some minor cosmetic blemishes and show signs of wear. Sorry). 

And in the time we were busy doing our best to wear out the first three impact drivers, four more came in from other manufacturers. While those four latecomers didn’t have the honor of being passed around half the metropolitan area like the first three did, they definitely received respectable workouts.

So, what was intended as a quick overview of three new machines has turned into a roundup of the best 12-volt impact drivers out there.

Because they rotate screws with a series of hammer-like impacts, the operator’s wrist isn’t under constant torque. Even driving dozens of screws is less tiring on the wrist than with a standard drill/driver.

Universal appeal

A word of caution: Impact drivers are addictive. While I had them for testing it seemed I could always find a use, no matter what I was working on. From driving lag bolts, building cabinets, to maintenance on my dirt bike. Every one who visited my shop ended up driving a collection of screws and lag bolts into a piece of red oak 4x4 I had on my bench to test the impact drivers. Drive in, drive out, drive in, drive out. They drive difficult fasteners so easily you have to drive and remove several before you really believe your eyes.

I have to admit right up front that I’m not an expert in power transmission, battery design, or scientific torque or electronics evaluation. What I based this review on was the input of both the professionals and hobbyists who used these tools, and my experience as a user. The first “cordless” drill/driver I carried to a job site was called a brace. I have been lucky enough to use or test just about every kind of corded and cordless introduced since then, and I’ve driven enough deck screws and drywall screws to consider myself an expert user.

I started this review with the idea of picking a winner – the one impact driver you need to run out and buy today – but that didn’t happen. I found that different users, for completely different reasons, had their own favorites. We shouldn’t be surprised. With the cost of developing, tooling, advertising and manufacturing a new product, no major manufacturer is going to intentionally put a substandard tool on the market. They vary in features, price point and intended market, so this wasn’t intended to be an “even match” of models, or anything else. However, I found the quality of all of them met or exceeded my expectations. The bottom line is that they all drive fasteners better than any drill/driver.

Impact drivers are generally available in models ranging from 9-18 volts (plus a couple of odd-ball power levels like 19.2, and the newer lithium-ion models that go even higher), but I chose the 12-volt versions of these tools simply because 12-volt tools strike a good balance in the power range. Enough power to do just about any chore you could want, without the weight and bulk of larger battery packs. Of course, if you’ll rarely challenge an impact driver with heavy-duty use, a 9-volt model may work for you just fine. Likewise, if you’re a deck installer who’ll give one a workout every time you pick it up, a more-powerful 18-volter might be what you need. I prefer to carry the lighter 12-volt tool and an extra battery if needed, even though impact drivers have a battery life that seems much longer than using drill/drivers for the same chore. 

The drivers tested came as kits that included the impact driver, one or two batteries, a charger and case. Just about all the manufacturers of these drivers also offer other impact drivers with more and fewer features, and higher and lower voltages (as well as some corded ones). 

DeWalt DW052K-2

The DeWalt received high marks from our crew of testers for toughness and value. The poor DeWalt was also the one that seemed to receive the largest number of “drop tests” from ladders and two trips from the roof of my motor home to the ground. It is a no frills, tough tool, but it has one of the least-powerful battery packs in the roundup. This driver was the favorite of a professional mechanic who preferred the lack of features – such as a light to break when he threw it under a car. I found the trigger to be less sensitive than the Makita and Panasonic triggers, and the motor/transmission to be among the noisier that we tested. The grip was comfortable, and it definitely will stand up to abuse. 

With a street price of about $188-$199 for the kit that includes two batteries, this little DeWalt is a good deal.

Makita 6980 FDWDE

Makita gave their unit the highest motor-to-grip angle of all those covered in this article, giving a far different feel and balance than the horizontal DeWalt. (Of all the drivers covered here, only the DeWalt and the Bosch 23612 have near-horizontal motor angles.) Users either loved it or hated it. I found the high-angled head made the balance perfect for me, and made working in awkward positions like inside a cabinet much easier. 

At first, I thought the little LED built into the casing right under the chuck was just a cute add on, but the more I used the driver the more I appreciated the extra light. Maybe it’s a function of my age, but cabinets seem way darker than they used to be, and the LED made finding and engaging screw heads easy. 

While it may have “lagged” behind the others a bit when it came to removing lag screws, the Ridgid right-angle driver was the only one that could fit inside the drawer compartment of this chest to remove and replace screws.

darker than they used to be, and the LED made finding and engaging screw heads easy. 

The battery pack lasted long enough to hang all the drywall in a shop ceiling without changing batteries. A comfortable grip combined with the angled head made this my favorite driver. It just seemed to always be at the right angle with the least strain on my wrist. This driver also suffered a quite a few “drop tests,” including a couple onto the concrete floor of my shop, and escaped with only cosmetic damage. 

Priced at $199-$219 on the street, the kit includes two batteries.

Panasonic EY7201GQKW

Panasonic has long been an industry leader in battery technology, and this driver’s battery pack reflects this. At 3.5 Ah, it was the longest-lasting of the three we passed around town. I gave it a bit of stamina testing on my own, and found it still going strong when I quit driving 3/8" lag bolts one after the other because it just wasn’t fun anymore after 20 minutes. 

This unit, which is a successor to their earlier model EY6506, has a very bright LED built into the motor casing below the chuck like the Makita, and a retractable belt/pocket hook. As with my initial reaction to LEDs, my first thought on the retractable belt hook was that it was one of those little gimmicks that look good in advertising, but I’d never bother using. Wrong. It is really great when you are not wearing a tool belt, standing on ladder, to be able to hang the driver from your belt or pocket while fishing around for another screw or holding a workpiece in place. 

Great ergonomics, smooth trigger, belt hook, light, good batteries and a strong, quiet, smooth motor might make this a contender for best overall for you. (Which may account for why it was also the hardest to get returned when loaned out; those that liked it had a hard time parting with.) This impact driver was the only one in our group with two impact torque settings, with the lower “gear” really seeming to have more torque than some of the others. But, with a street price of $220-$245 for a kit that includes two batteries, you’re definitely paying for what you get. 

 As I mentioned earlier, we received four additional models, but didn’t have the opportunity to loan them out to half the neighborhood for in-depth abuse in the same way we did with the three above. However, we gave them several weekends of intensive shop thrashing to see what they had to offer.

Black & Decker FS1202ID

Easily the least expensive in the bunch at about $70 at your local home center, the Black & Decker Firestorm driver is a good contender for household use. Although it has one of the lowest torque ratings of those tested and isn’t likely to stand up to rigorous use on a job site, it still managed drive both conventional screws and lag screws respectably. 

This model had the second-highest motor-to-grip angle ratio (only a hair less than the Makita, in fact) giving it a very comfortable grip. Intentional durability wasn’t tested with this one, but it wasn’t really necessary – it was dropped once in the parking lot here at the office, once off the editor’s desk, and once onto a concrete garage floor with no damage.

The kit includes two batteries, and is the only driver we tested that came with a generous 15-piece assortment of hex-shank drill bits, driver bits, and nut drivers. 

With a torque rating of only 800 in. lbs. it doesn’t have nearly the head-to-head power of the others, but it’s a good cost-conscious choice for less heavy-duty use.

Bosch 23612

This driver was a real workhorse; its smooth (but somewhat loud) motor was the most powerful in the roundup at 2,800 rpm, 3,200 ipm, and with a torque rating of 1,150 in. lbs., it drove every screw it met with ease, and then some, for a long time between charges. Like the DeWalt, the motor-to-grip angle of the Bosch 23612 Impactor is nearly horizontal, but the grip is solid and comfortable. The belt hook retracts when not needed, and can be swapped from the left side to the right by removing a screw at the base of the grip, or removed if you have no need for it. This was one of only three drivers tested – the Ridgid and Hitachi were the other two – that offered any kind of on-board bit storage, which seems like something all drivers should have as. The very bright LED is mounted at the base of the grip, and can be rotated up and down to give the best lighting angle. It’s really too bad that this one didn’t come in earlier, as it likely would have been one of the favorites of those we passed around our extended testing group. 

With street prices of $190-$220 for a kit with two batteries, this driver gives a lot of bang for the buck.

Hitachi WH12DMR

At 3½ lbs., standing just 8¾" tall and with a motor casing just under 6" from nose-to-tail without a bit installed, the Hitachi is easily the most petite driver in the group. Don’t let the size fool you, however. Packing 2,600 rpm, and matching the Bosch’s torque rating of 1,150 in. lbs., and impact range of 3,200 ipm, this little guy easily held its own against its larger blue test companion when it came to driving power and run time. In spite of its power, this was also one of the quieter units in the test group. With a high motor-to-grip angle and diminutive size, it was extremely comfortable to hold and use in spite of the fact that it’s the only one tested that lacked the soft rubbery over-mold on the grip. This tool was a pleasure to use for long periods of time.

Tested in a piece of hard white oak, the left screw was driven with a standard drill/driver, while the one on the right was set with an impact driver. Because the rapid impact action of these drivers reseats the bit with each impact, stripping screws is rare.

The Hitachi had the most unusual belt hook and LED arrangement of the lot, combining the two into a single accessory that mounts to either side of the grip. The light is also the only one in the group that wasn’t powered by the tool when triggered – the light has its own on/off switch and its own battery compartment, meaning that it can be removed and used as a flashlight. 

With prices ranging from $189-$200 for a kit with two batteries, the Hitachi is a good deal.

Ridgid R82233

The Ridgid was the only dedicated right-angle impact driver in the roundup. If this had been an even match of models, the Ridgid would have been outclassed by all of the other conventional impact drivers we tested. The impact mode is very loud, and with a torque rating of only 700 in. lbs. – the lowest in the group – the driver had difficultly removing lag bolts the other models both drove and removed easily. I personally didn’t care for the location of the paddle-style switch, but anyone with a lot of experience with similar pneumatic tools may find the switch shape and location quite familiar. There’s no LED, but considering how this driver would normally be used, a light wouldn’t help much anyway.

That said, this wasn’t an even match of models, so even though it’s not quite the same species as the other impact drivers it has some abilities they don’t. The right angle head and long length let it get into places that no conventional driver can. With a standard Phillips bit in place, it needs only 4" of clearance to reach its target, which makes it a natural for work in places like small drawer openings and between workpiece components. It’s also the only model tested that has a protective rubber cover around the business end to keep from scratching workpieces, and a rubber-bottomed battery that keeps it from sliding when you set it down. The Ridgid kit is the only one with a single battery, but the 20-minute charger – and second-lowest kit price in the group at $129 – makes that less of an issue.

If you don’t really have a need for driving hundreds of lag screws, but you do need a driver that can reach otherwise impossible fasteners, the Ridgid may be just what you’re looking for. 

These tools won’t spell the end of the cordless drill/driver, but they will change which tool you reach for when you need driving or loosening power, or when you have a lot of fasteners to drive. Before testing these impact drivers, you could never have convinced me that they would be so superior to a drill/driver that I’d be willing to plunk down my money for something this specialized. Now I’m completely sold. 

It doesn’t matter if you are bolting together a swing set, screwing down decking, or hanging a cabinet (or, for that matter, undoing any of those tasks), impact drivers perform at a completely different level than your drill/driver.

– Tim Rinehart is contributing editor to Woodcraft Magazine.

HOW IT WORKS

An impact driver works by combining a hammering action with rotational action, with the hammer blows – impacts – acting in the rotational direction. (Although similar to the idea behind hammer drills, the force of the hammer blows in an impact driver is in the direction the screw is spinning; hammer drills apply their force in-line with the drill’s travel into the workpiece.)

To accomplish this, impact drivers have an internal hammer/anvil arrangement that engages when the driver senses a load. That’s why an impact driver starts out sounding like a regular drill/driver at first, then begins “clacking” once the screw resistance hits a set level.

When this resistance is met, it compresses a spring inside the gear assembly and engages a cam mechanism that forces the hammer to strike the anvil. When the hammer impacts the anvil, it momentarily doubles or even triples the amount of torque in the direction of rotation. Depending on the driver’s design and the amount of load, this hammering action can occur up to 3,200 times per minute, delivering smooth, high-torque driving power as needed.

To understand the process, consider the experience of changing a tire with an angled lug wrench. If the lug nuts have been in place a long time, they’re likely “frozen” in place very tightly. Turning the lug wrench as hard as you can – delivering as much torque your arms can normally muster – sometimes isn’t enough. But if you whack the angled arm of the lug wrench with the palm of your hand several times, you can sometimes free the nut to start it spinning. Each time you hit the lug wrench, you’ve momentarily applied more torque to the wrench than you normally have available through regular muscle power alone.

You’ve just imitated the action of an impact driver. — A.J. Hamler

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