63 VIDEO WHY IMPACT DRIVER ARE BETTER THAN DRILLS

I don't know any builder who's used an impact driver who then goes back to

using a cordless drill to drive deck screws and lag bolts. That's because they

work so well. But what you might not know about is what goes on inside a tool like

this. So let's go down to my shop. I'll pull one of these apart and we'll take a

look inside. The main thing about cordless impact drivers is how light and

short they are. That makes the tool easier to use. And to make that happen

engineers have used a few techniques that I want to show you right now inside

the tool. The first thing you notice about the tool when you take it apart is

just how short the motor is. If you pull it apart you find that the windings are

less than 3 quarters of an inch long. Here you can see them here. Now tool

engineers get the power they need from a motor this short by using four instead

of two powerful magnets around the stator of the motor. Over the last five

years I've taken apart dozens of tools like this for stories but I've never

noticed this feature before. Instead of the brushes being replaceable individually they come as part of a module that you can unplug. The brush

comes ready mounted in a holder with a coil spring that applies pressure to the

brush so it pushes against the rotating part of the motor. This makes it easier

to maintain the tool and also lets the replacement brushes work better because

they're in perfect alignment with the rest of the motor. The main thing that

separates the performance of an impact driver from a regular drill as far as

screwdriving is concerned is the way the shaft of the tool turns under load. With

a drill it's just a straight rotation. With an impact driver it's a combination

of forwards and backwards movements that happen more than 40 times a second. This

is the impact action of the tool and it happens thanks to this drive mechanism

here. It's a lot simpler than you'd imagine. You've got this disc right here

that's supported by a powerful spring on the back. These two cogs interlock with

these two pawls right here. When the tool is operating under a no load situation

the engagement is complete and full just like it would be in a drill. But when the

tool gets under load, because this back disc is spring-loaded, it backs off

slightly and allows the tool to slip, as I said, many times a second producing that

forwards backwards motion that gives the driver tip much more traction in screw

heads. They're much less likely to cam out. For a detailed tour inside impact

drivers, take a look at my article in Canadian Contractor magazine