Power drills have tendency to shear off screw heads
Power drills have tendency to shear off screw heads
You no doubt already have a cordless drill/driver in your home or shop, and have come to really appreciate everything these highly versatile tools can do, from drilling holes to driving a wide variety of fasteners. But you may have also come across a few of their limitations as well. Most lack the raw power for driving large fasteners like lag bolts. And their high rotational speed can shear off screw heads at the most inconvenient times, especially when fastening long screws or working with harder lumber.
The solution might be to add an impact driver to your arsenal of cordless tools. An impact driver probably won't replace your cordless drill, but it certainly provides a great complementary tool for a number of different tasks.
So what's the difference between a drill and an impact driver?
A drill utilizes a motor to provide rotational motion only. In order to drill a hole or drive a screw, you need to provide the strength against the drill to keep the bit in contact with the material or the fastener.
With an impact driver, you still have a motor initially turning the chuck, and when there's little resistance against the bit, the impact driver works pretty much like a conventional drill. But when the bit senses resistance, the impact driver automatically changes modes, and an internal hammer and anvil mechanism engages. This slows the chuck's rotational speed, but applies a great deal more torque (rotational force), so you can drive long screws or bolts with considerably less effort and with less chance of shearing off the heads. The typical impact driver provides about three to four times as much torque as a conventional drill of the same voltage, in a smaller and lighter package.
So with all that, are there disadvantages to an impact driver? A few. For one thing, they're noisy. When they switch to their impact mode -- which, by the way, they do without warning -- they make a loud and somewhat irritating noise (think about those wrenches in a tire store), so you need to be wearing hearing protection.
Another disadvantage is that impact drivers have a 1/4-inch hex chuck, not a conventional chuck, so you can only use hex bits in them. Most screwdriver bits and bit holders are this size, so that's not a big deal. However, if you want to drill holes, you'll need to invest in drill bits with a 1/4-inch hex shank on the end.
Finally, expect a bit of learning curve with an impact driver, especially if you opt for one of the higher voltage ones. Because the impact mode kicks in unexpectedly, and because of the high torque, you need to get a feel for these tools. However, that's not especially difficult, and you'll find the trade-offs are well worth it especially if you have a big outdoor project like a new deck to tackle.
Shopping for an impact driver
As with cordless drills, the best way to buy an impact driver is in a kit, with a charger, a couple of batteries, and a storage case. If you're in the market for both an impact driver and a drill/driver, you can get some great combo kits that have both and save even more money.
Many kits come with a choice between standard 1.5-amp-hour (AH) and extended-run 3.0 AH batteries. With the extended-run batteries you'll be able to work longer between charges, but the trade-off is a higher initial cost and more battery weight. With a two-battery kit and a 30-minute fast charger, you may or may not find the extended-run batteries worth the extra investment.
Here are two professional-grade kits that are well worth considering, with their approximate retail kit prices:
DeWalt 20V Max 1/4-inch 3-Speed Impact Driver (Model DCF895C2 w/2 1.5 AH batteries, $279; Model DCF895L2 with two 3.0 AH batteries, $349): This tool has a nice, comfortable rubber-molded grip, with protective rubber pads where you set the tool down. It has a brushless motor for longer life, and a battery fuel gauge. The chuck has a nice push-button release for one-handed accessory changes, and there are three LED lights around the chuck for great visibility.
It features three speed/torque ranges to match the material you're working with: 0-950 RPM and 500 inch-pounds of torque; 0-1,900 RPM and 900 inch-pounds; and 0-2,850 RPM and 1,500 inch-pounds. Tool length is 5 1/4 inches, weight is 3 pounds. The complete kit includes the impact driver, fast charger, two batteries, reversible belt hook, accessory storage clip, and hard-shell case.
Milwaukee M18 1/4-inch Hex Impact Driver Kit (Model 2653-22CT w/2 1.5 AH batteries, $229; Model 2653-22 with two 3.0 AH batteries, $299): The tool fits nicely in your hand, with a nonslip grip and rubber cushioning. There's a bright, trigger-activated light, and the mode selection is done with a convenient button rather than a switch, with a light to indicate the selected mode. The batteries also have a lighted, push-button fuel gauge.
This impact driver also has three speed/torque modes, so you can compare the two and see which ranges might work better for you: Milwaukee's is 0-850 RPM and 200 inch-pounds of torque; 0-2,100 RPM and 700 inch-pounds; and 0-2,900 RPM and 1,600 inch-pounds. Tool length is 5 1/2 inches, and weight is 3 pounds. The complete kit includes the impact driver, fast charger, two batteries, reversible belt hook, and hard-shell case.
Milwaukee 35-piece Impact Drill and Drive Set (Model 48-32-4402, $29.97): The high torque of an impact driver can twist and shear standard bits and sockets, so you really need to invest in the right bits to accompany your new impact driver. Milwaukee, for example, offers a beautiful set at an affordable price that's specifically engineered for use with impact drivers. This set gives you five drill bits, three nut drivers, two socket adapters, two long screwdriver bits, and a bit holder with several different screwdriver bits, all in a nice fitted case.
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