3

When I watch videos on using a table saw safely, it almost always is about kickback. I realize, that kickback is the most dangerous hazard, but are loose teeth, that could become projectiles, when disconnecting from the blade really no issue ? For example in case of an manufacturing defect.

Or am i missing something?

  • I don’t think anyone will think less of you for inspecting the blade. – mreff555 Dec 15 '18 at 20:09
  • If there is a manufacturing defect in the blade, it would potentially be hard to see. – user2664856 Dec 15 '18 at 20:12
  • Probably impossible but I suppose you could make sure it hasn’t lost any tips – mreff555 Dec 15 '18 at 20:13
  • 1
    A lot of things could have defects. The motor could have a shorted armature and catch on fire when you turn it on. Prevent what you can but you can’t prevent everything. – mreff555 Dec 15 '18 at 20:15
  • Yeah right (not really) ... that is more or less the question. Maybe there are a few ways to protect against this. – user2664856 Dec 15 '18 at 20:24
5

Loose teeth on a modern table saw blade are indeed a thing to be concerned about. It would be anybody's guess as to where the loose tooth would fly if it came off the blade. As many readers here may know the most popular blades in use today are the type with carbide tips bonded to the tooth cutouts on a blade core.

It is possible that there is a history of table saw safety over many years that has contributed to the current body of knowledge, articles and videos. Historically the saw blades in use twenty or thirty years ago were much more likely to be steel blades with teeth that were sharpened and set with alternate facing cutting edges that were bent slightly in each direction from the plane of the blade body. It is much less likely that a tooth on a blade would come flying off when the teeth are all cut and formed from the core material of the blade. So in the past it was less likely that saw blade destruction would be stressed in any particular way in safety information.

It is also true that warnings about trying to use blades that are dull and worn would have been more prevalent. The modern carbide tipped saw blades in common use today stay sharp much longer. And even if they do become slightly dull the integral design of the blades upon which the carbide tips are mounted prevents a lot of the binding of the saw blade in the kerf that is experienced with an all steel saw blade when the teeth have lost most of their set.

4

In theory it's not a serious issue. The tooth of a table saw blade travels at a linear speed around 146 feet/second, so if a tooth suddenly came loose you'd be faced with a tiny piece of metal travelling just under 100 mph. In reality the most likely result is it breaks and lodges in the wood when entering the kerf, or exits the kerf and travels straight down. [FWIW the teeth of a 7.25 circular saw blade would seem to be more of danger since they're similar size and run at much higher rpm.]

While a hundred mile an hour tooth sounds bad, it's not a huge amount of kinetic energy. It's much less than a baseball, probably more than a pellet gun. (A smaller mass travelling at 750 ft/s.) Certainly enough to merit eye protection, but highly unlikely to kill or seriously injure.

A much larger concern would be some sort of catastrophic blade failure flinging both lumber and large pieces of metal around. Large kicked back pieces have quite a bit more kinetic energy than a tooth. A prudent precaution is to let the saw spin freely for a bit prior to cutting. Grinders, which use resin blades typically suggest allowing the blade to run for 15s away from your face to be sure the glue isn't failing before you start grinding.

The real danger with a table saw is that accidents happen quickly in close proximity. That's compounded by the fact that the saw typically has enough power to accelerate anything on it to 100mph. While a tooth may present a limited danger getting hit by a 2x6 at 100 mph is an entirely different ball of wax. (Big leaguers shrug off baseballs, but don't want to be hit by a car travelling the same speed!)

  • 1
    I think your math is off. My Grizzly table saw spins at 4200 rpm. The blade is 10" in diameter. By my calculations, that means that the teeth travel at 10 * pi * 4200 inches per minute. This is about 11,000 ft per minute or 659,715 ft per hour or about 125 miles per hour. – Edwin Dec 15 '18 at 21:00
  • 1
    Duh, brain cramp. It should be 146 ft/sec which works out to 99 mph. – Matthew Gauthier Dec 15 '18 at 22:31
1

The biggest problem with them is that they go missing on modern blades easily, causing kickback. Remember, the teeth are typically soldered on and if they come off, it's most likely going to be at the point of contact with the material you're cutting.

I recently had my miter saw kickback. I had bought a cheaper blade and discovered that several teeth had come off. None of the teeth I found were more than a foot from the saw.

If you want to reduce the chance of missing teeth, try buying higher quality blades.

  • Could you feel any imbalance or wobble/shimmy while the blade was spinning? Guessing not cos of the small weight of a tooth. – Criggie Dec 16 '18 at 4:47
  • 1
    @Criggie I was only missing 5 teeth on a 40 tooth blade. It was the two next to each other that did me in with kickback (block flew off the fence and hit my hand) – Machavity Dec 16 '18 at 13:53
0

Anything coming off the blade is a problem, for sure. With table saw blades, though, there is little chance of that happening, so it doesn't get as much attention. Kickback is a much more prevalent issue, therefore it gets more attention.

Kickback (and most other well-known table saw dangers) is a preventable danger (for the most part), while a manufacturing defect is all but undetectable by the end user. You can certainly inspect the blade before use, to look for signs of metal fatigue, loose teeth, or other dangers, but most table saw blades are thrown out because they become dull, not because they break. Of course, if you happen to hit a piece of metal you'll most certainly want to inspect your blade and perhaps replace it, but during normal use the blade will remain in one piece, almost guaranteed.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.