Injuries from Flying Carbide teeth

[Rickbird]

I don't know if starting a new thread is a good idea or not but anyway...

Looking at that untoothed Blue Thunder blade that Ryan has showed made we wonder about injuries when this type of catastrophe occurs.

On the other hand, has there been any kind of reported injuries with flying carbide embeding in people? I wonder if these flying pieces have the kind of momentum to actually cause piercing of the skin. (My guess is that they would not)
What is the knowledge out there about this?

[willr]

Originally Posted by Rickbird

I don't know if starting a new thread is a good idea or not but anyway...

Looking at that untoothed Blue Thunder blade that Ryan has showed made we wonder about injuries when this type of catastrophe occurs.

On the other hand, has there been any kind of reported injuries with flying carbide embedding in people? I wonder if these flying pieces have the kind of momentum to actually cause piercing of the skin. (My guess is that they would not)
What is the knowledge out there about this?

I'll ask the boss -- she sees a lot of the nail gun and table saw users professionally -- mostly nail gun users -- so don't pull the plug on your table saw yet.

[mbowler]

My guess is that teeth that are ejected from the blade are ejected the same place the sawdust is going... which is generally not at the operator. Unless the tooth comes loose at a point when it is not striking the object being cut (seems unlikely).

Nevertheless, there is a general safety rule to never stand directly in front of a vertical cutter. Good one to follow in my opinion.

Cheers,

Mike

[ed on manitoulin]

I,ve fortunately never had any experience with teeth coming out of sawblades, but about a month ago I was routing some maple stair stringers & I snapped off a 1/2" routerbit. My Makita 3612? I think has 22,000 rpm. Within a second of the bit snapping off, the cutter portion of the bit was laying lifeless in the treadspace. It barely moved from where it snapped!

[Gene45]

I once asked a supplier of brush trimmer blades why I could not use a normal saw blade instead of their 1" arbour blades.

The reply was that people would use carbide blades and injure themselves. Probably.

I have had carbide teeth disappear from table saw/radial arm blades, and a circular saw blade, and never knew where they went.

If they came free at full speed, they would almost certainly penetrate the skin. I believe the rim speed is nearly 9000 feet per minute, or 300 feet per second.

According to:

http://www.velocitypress.com/air_rifle_ballistics.shtml

the velocity of a .22 rifle drops to 400 fps at 70 yards.

And the carbide tooth is sharper than a 22 bullet. Ouch!

[redlee]

I have been Machining for 30 Yrs. Carbide Breaks quite easily,and can come at you fast enough to kill you, dont underestimate what any kind of broken tool HSS or Carbide can do.

[Gene45]

Originally Posted by Gene45

If they came free at full speed, they would almost certainly penetrate the skin. I believe the rim speed is nearly 9000 feet per minute, or 300 feet per second.

Of course I was using my new Apple clock that runs on Quicktime, only 30 seconds per minute.

The right answer is 150 fps. So Sorry!

[Max In Sudbury]

A table saw motor usually rotates at 3450 RPM. With a 10" blade, the outer speed of the blade is roughly 102 miles per hour. Given the light weight of the carbide, it is unlikely that it would cause more than an abrasion or bruise - very unlikely to penetrate your skin or clothing. It will, however, damage your eye.

According to the interweb, a Colt 45 fires a bullet at approximately 550 miles per hour, while a .22 caliber handgun fires at over 2000 mph.

As a further reference, raindrops fall at around 20 miles per hour and a large hailstone can fall at approximately 100 miles per hour.

All that said, several years ago, I dropped a very small piece of wood (I believe it was poplar and maybe 1/2" x 1/2" x 1/2") on my spinning table saw blade. It hit the blade, bounced up and hit my left index finger, right on the middle knuckle. It hurt like he77, and to this day, my finger does not bend properly and still has minor pain.

[J.P. Rap]

I have seen (as many of you have) pictures of kick back resulting in a hold in a block wall. I doubt the carbide would fly off with any less force then a piece of wood gets kicked back. A tooth could (in theory) get damaged while in the wood and not break free right away. If it breaks free when it's traveling toward you, it will travel in a straight line...toward you.

A number of years ago there was a similar thread on this forum. One of the members related a story of a friend who was hit in the leg by a piece of carbide that broke off a router bit. The fragment entered his leg and severed the main artery (or is that a vein?). The poor guy bled to death before anything could be done. IIRC this happened on the job and there was immediate aid but there was nothing anyone could do. Sad story.

[Max In Sudbury]

Originally Posted by J.P. Rap

A number of years ago there was a similar thread on this forum. One of the members related a story of a friend who was hit in the leg by a piece of carbide that broke off a router bit. The fragment entered his leg and severed the main artery (or is that a vein?). The poor guy bled to death before anything could be done. IIRC this happened on the job and there was immediate aid but there was nothing anyone could do. Sad story.

IIRC it was a piece of wood from kickback that pierced the artery in the person's stomach. There may have been another one where a splintered board from kickback pierced an artery in the individual's leg. They were posted on other forum as well.

The mitigating factor that would likely (and I say likely) prevent carbide from penetrating is the weight.

Again, I'm saying likely - so make sure to be safe.

[Ryan in Edmonton]

Rickbird, I think this is a great topic to start. As woodworkers we should all be aware of the dangers of the hobby, and sharing experiences about such incidents as carbide teeth flying off saw blades is valuable to all.

I looked at the manual and found that the no load speed of my 12" Bosch miter saw is 3800 RPM. Using this site:
http://www.sharptool.com/reference_tables.html#RimSpeed
I figured that a 12" blade at 3800 rpm, the rim speed is 11938.11 feet/minute.

Using this site:
http://www.convert-me.com/en/convert/speed

I converted that to more common measurements of velocity. The teeth of my saw will spin at 199 feet/second = 135.7 miles per hour = 218.3 kilometers per hour.

Not quite the speed of a bullet, but pretty darn fast. Of coarse that is no load speed, so add a load, and it slows down. Then consider the fact that the teeth likely hit wood before or during flying off (in my case), then they probably would have slowed down more.

I don't know exactly what injury I may have sustained if the teeth or even the wood splinters had hit me, but I'm sure glad I didn't find out.

But I sure think it is worth it to spend the money on a higher quality blade where the processes for making the blade and attaching the carbide are likely better and more strictly controlled. Hopefully that seriously limits the chance of carbide coming off or entire teeth breaking at the gullets. I've always said, you get what you pay for, and I guess it was wishful thinking to think a $55 12" blade would hold up much better that it did.
Today I spent $160 on a new blade from a reputable industrial blade supplier. I'm excited to see the difference quality makes.

Ryan

Oh, if down the road someone has no idea what I'm talking about, here is my other thread. http://forum.canadianwoodworking.com...ad.php?t=27978

[J.P. Rap]

Originally Posted by Max In Sudbury

IIRC it was a piece of wood from kickback that pierced the artery in the person's stomach. There may have been another one where a splintered board from kickback pierced an artery in the individual's leg. They were posted on other forum as well.

The mitigating factor that would likely (and I say likely) prevent carbide from penetrating is the weight.

Again, I'm saying likely - so make sure to be safe.

Those might be different guys. I clearly remember it was a piece of carbide from a router bit.

[Tom Hintz]

Every once in a while I get photos and descriptions of injuries in woodworking. Last summer one of those injuries was of a man who dropped a wrench he was using to adjust his miter gauge attachement. The wrench glanced off of the miter gauge fence and directly into the spinning table saw blade. Several teeth were sheared off and two lodged in his forehead, penetrating the skin far enough that they had to be removed in the hospital. One required opening the wound a bit by the doctor (cutting) to get at the broken tooth to remove it.
I never put photos like that on my site because I have agreements with many schools and lots of family-type viewers. But I think it is important that we never assume something probably won't hurt us that bad. Given the right situation - which always happens at exactly the wrong time - just about anything we use in woodworking or anything else really can hurt us.
Best not to tempt the evil woodworking spirits!

[Ryan in Edmonton]

Originally Posted by Tom Hintz

Every once in a while I get photos and descriptions of injuries in woodworking. Last summer one of those injuries was of a man who dropped a wrench he was using to adjust his miter gauge attachement. The wrench glanced off of the miter gauge fence and directly into the spinning table saw blade. Several teeth were sheared off and two lodged in his forehead, penetrating the skin far enough that they had to be removed in the hospital. One required opening the wound a bit by the doctor (cutting) to get at the broken tooth to remove it.
I never put photos like that on my site because I have agreements with many schools and lots of family-type viewers. But I think it is important that we never assume something probably won't hurt us that bad. Given the right situation - which always happens at exactly the wrong time - just about anything we use in woodworking or anything else really can hurt us.
Best not to tempt the evil woodworking spirits!

So the guy was making an adjustment with a wrench while the saw was running??? Thats just plain foolish.

I'm not surprised though that the teeth easily penetrated his skin. There was some suggestion that they wouldn't. I suppose it would depend on where on the body they hit. My cushy stomach might give a little more than my forehead, so the teeth may not penetrate with less resistance behind the skin (i.e. flab vs. skull). The days of my rock hard 6 pack are gone....

Ryan

[John Bartley]

My cousin used to own a circular sawmill - something in the 52" diameter size, run by a Cockshutt tractor. Between the operator and the blade hung a sheet of cloth mesh - something like a burlap window screen. Every once in a while, one the insert carbide teeth would work loose and come flying out. If it happened to come in the direction of the operator it would hit the cloth and fall to the ground. I saw a couple hit the cloth and they never came through. I'm not saying it isn't dangerous, I'm just saying that wearing the correct work-wear, safety gear etc. is a good idea.

cheers

john

[JoeBoxer]

Yeah,

Thanks alot guys. I'm selling all my power tools and getting hand tools.

Anybody want to trade a number 8, 5, 4, and other hand plane for a 13" jointer.
Some good quality hand saw for a 1 1/2 hp delta TS (induction motor) with 3 sets of brand new blades (60/80/100 T), with a 60" Beisy fence.
I'm not sure how to replace my router though, some ideas please.

[Gene45]

Originally Posted by John Bartley

My cousin used to own a circular sawmill - something in the 52" diameter size, run by a Cockshutt tractor. Between the operator and the blade hung a sheet of cloth mesh - something like a burlap window screen. Every once in a while, one the insert carbide teeth would work loose and come flying out. If it happened to come in the direction of the operator it would hit the cloth and fall to the ground. I saw a couple hit the cloth and they never came through. I'm not saying it isn't dangerous, I'm just saying that wearing the correct work-wear, safety gear etc. is a good idea.

cheers

john

The force of the impact depends on how quickly it happens. The loose hanging "cloth mesh" will slow the piece down over a few inches, and result in low forces.

A skull will stop it very quickly, or else you are dead.

The formula is in the form of:

F = (mass x velocity) / duration of collision.

So if it stops in zero time, the force becomes infinite, which is, like , really, really, big,

[willr]

Originally Posted by Gene45

The force of the impact depends on how quickly it happens. The loose hanging "cloth mesh" will slow the piece down over a few inches, and result in low forces.

A skull will stop it very quickly, or else you are dead.

The formula is in the form of:

F = (mass x velocity) / duration of collision.

So if it stops in zero time, the force becomes infinite, which is, like , really, really, big,

FWIW -- the boss does thousands of exams a year -- no known "flying carbide teeth injuries" -- none among the 25 or so others in the group who process at the same rate. But that's just in this area and the three other hospitals she has worked...

So, it's pretty rare I gather -- for whatever reason.

Nail gun accidents are way up there. They form the majority of incidents from the carpenter crowd -- mostly home owners with a nail gun and too little concern for safety, and a distant second is carpenter/framers. Not my words...

People trimming their digits (table saws, band saws, circular saws, knives etc.) are a weak second.

So if I were going to expend more effort here -- it would be on safe practices and procedures, and protective clothing.

If a carbide tooth does come loose from the table saw and hits me in the eye, considering the angle of projection, I doubt that I will be commenting on it.

I heard some lively anecdotes I would love to pass on (some that beggar the imagination) -- but they would identify people uniquely -- if not by name. sorry...

[Tom Hintz]

Originally Posted by Ryan in Edmonton

So the guy was making an adjustment with a wrench while the saw was running??? Thats just plain foolish.
Ryan

He said in his first message about the injury how dumb it was. He was just snugging up the gauge ater having adjusted it with the saw off, made a cut to confirm the setup and wanted to just check the bolt before going right into production on a bunch of cuts. He knows it was dumb but I suspect we all do things without thinking from time to time that when thought about later we would never do. I know he won't ever do it again anyway!

[Jim in Burlington]

Bandsaw blades that break scare me more. Bigger the blade the worse it is.