A second portable table saw with a riving knife!
Ever since portable table saws first appeared on jobsites, carpenters have been throwing away the guards, and for good reason: They’re difficult to remove and re-install; after they’ve been used for a few months, you can’t see through the plastic shroud, so it’s impossible to align the blade with a measurement mark; you have to remove the guard to make narrow rips or rabbets; and carpenters have always suspected that the splitters cause more kickback than they prevent. Those are a lot of reasons to set aside a saw guard.
Fortunately, tool manufacturers—prodded by governmental regulations—are upgrading the guards on portable table saws. Bosch was the first manufacturer to release a new guard system. On my website almost two years ago, I reviewed Bosch’s new Smart Guard System for their portable table saw. At the time, I learned that several tool manufacturers had been working on the same system together, so that every new portable table saw could be equipped with an easy-to-use guard system where the splitter converts to a riving knife. Up until then, the only way to install a riving knife on a portable table saw was by modifying the splitter, and that meant the shroud couldn’t be used again. But Bosch’s new Smart Guard System eliminates the need for modifying the splitter, allows carpenters to use the plastic cover or shroud, and converts easily into a riving knife simply by lowering the splitter down beneath the top teeth on the blade.
If you don’t know what a riving knife is, or how important it can be to your safety, pay attention! A riving knife acts just like the splitter on a table saw—it prevents the kerf from closing on the back of the saw teeth, which usually results in kickback. A saw kerf can close for a variety of reasons, either from pressure built up in the wood grain—especially in hardwood— or from a warp or twist in the board, which creates pressure between the rip fence and the teeth at the back of the blade. Kickback is one of the most dangerous things that can happen while using a table saw. Many carpenters have lost fingers—or worse—because of accidents due to kickback.
Like a splitter, a riving knife mounts behind the blade, but instead of projecting up over the blade, a riving knife is about 1/8 in. shorter than the top teeth of the blade. More importantly, a riving knife attaches to the blade carriage, so it travels up and down with the blade, staying at the same elevation, no matter how high or low you crank the blade. Some splitters don’t do that, which makes them impossible to modify. But the best thing about a riving knife is that it doesn’t have to be removed—ever, unless you switch to a smaller blade or dado set. Riving knives can save a lot of fingers. (For more on riving knives, read this article from Fine Homebuilding).
Bosch’s Smart Guard System revolutionized table-saw safety—mostly because it was the first easy-to-use guard that carpenters weren’t inclined to throw away! Bosch made the plastic shroud easy to see through, easy to remove, and easy to store right on the saw. They also made a splitter that converts into a riving knife quickly and easily: It takes only a few seconds to loosen the splitter and lower it into the riving knife position. If you’re not familiar with the Bosch Smart Guard System, the tool review article referenced earlier discusses the system in greater detail.
The guard system on the DeWalt saw is very similar to Bosch’s guard system, but there are many other benefits to this saw. First of all, the DeWalt 745 weighs less than 45 lb., while the Bosch 4100 comes in at 60 lb.! The Bosch saw does run much quieter and more smoothly, but the weight difference is so dramatic that many carpenters will be tempted by the DeWalt saw, especially considering that the DeWalt saw costs as little as $400, while the cheapest I’ve seen the Bosch is $550.
Because the DeWalt saw is so much smaller, I was able to get a smaller Rousseau Saw Stand, which saves on the overall weight and space. The only real compromise I’ve had to make with this saw is the noise: This new saw is a screamer.
I tried the saw with the factory blade from DeWalt, and also with a Forrest blade, and found little difference in the noise—although the saw cut beautifully and ran more smoothly with the Forrest blade.
Another problem I have with the DeWalt 745 is the blade elevation mechanism—it takes over 40 revolutions of the crank to raise the blade fully!
At first, I thought the smaller gear teeth would be prone to sawdust buildup, but after using the saw for more than a year, I’ve found that the mechanism still works smoothly, if slowly.
Fortunately, the engineers who designed the Bosch and DeWalt guard systems paid a lot of attention to the way we use table saws. Both guards are split down the middle, so the operator can see the blade looking from both the front of the guard and through the top of the guard. Because you can see through the top of the guard, you don’t have to lift or remove the guard to check that the blade is hitting a measurement mark.
|DeWalt has definitely improved on Bosch’s clumsy and difficult-to-operate guard latch.
The 745 guard slides easily onto the back of the splitter/riving knife—simply lift the front of the guard and slide the rear ring and pin over the hook in the splitter.
|To lock the guard in place…
|…press the large thumb latch down.
|To remove the guard, lift the latch up.
Nothing could be simpler. The latch on the DeWalt guard operates smoothly and easily—a significant improvement on the Bosch latch, which is difficult to grasp, and it sticks.
DeWalt’s easy-to-use hardware for storing the plastic guard under the saw is similar to the Bosch, so storing the guard and keeping it with the saw is no longer an excuse for not using the guard.
Trust me, this is one table-saw guard you won’t throw away in frustration.
To adjust the guard and splitter/riving knife, you have to remove the throat guard. But DeWalt made that easy, too. The throat guard is secured with a tool-free lock, and a finger hole makes it easy to remove the insert.
Converting the guard from a splitter to a riving knife means lowering the splitter until it’s just below the top of the saw blade teeth.
|Bosch uses a very small lever to release the splitter/riving knife.
On my Bosch 4100 saw, even in the locked position, the splitter/riving knife isn’t perfectly snug. I’ve tried tightening the lock nut to increase the pressure, but the bolt is so small, I worry that I might shear it off.
By comparison, the DeWalt splitter is secured with a T-knob that tightens and seats easily. You don’t have to remove the knob to lower the splitter.
|Just loosen the knob about three turns, and push the knob in, so the splitter can slip off the retaining pins. Then lower the splitter into the riving knife indexed position.
DeWalt tried to think of everything with this saw.
|They even ship it with a plastic push stick.
I guess, in a pinch, that’s better than nothing…
|…but my advice is to make yourself a proper push stick, one that doesn’t push towards the blade but over the top of the blade.
That’s another great way to save fingers while working with a table saw!
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Please don’t try anything you see in THISisCarpentry, or anywhere else for that matter, unless you’re completely certain that you can do it safely.