disposable router bits - how safe?

[marq35]

I have used disposable router bits for some years. This is the type where the main shaft accepts disposable blades, usually with 2 or 4 cutting edges. These blades are held in by two grub screws.

Recently an associate mentioned that one had shattered whilst in use - luckily the bits not harming the user or anyone else nearby.

The question is - since in my normal work stance the blade is very close to my well developed stomach, I feel very much at risk and what can I do to minimise this perceived risk?

It has been suggested that as a minimum a leather apron should be worn ( I think perhaps two).

Perhaps a bullet-proof vest?

Any suggestions or comments or experiences?

Marq 35

[cyberben]

You'll always find someone who's got a story about a router bit flying out of control. Even a tooth on a saw blade can break loose and fly...

On the other hand, I think your best bet is to double check your cutters on the router bit each time you use them. Make sure all screws are tighten properly and everything's fine. Maybe you can take the habit of starting the bit at the slowest speed just to make sure everything's well balanced and in good working order.

Aside from that, there's very little you can do to protect yourself from a potential accident. Powertools are inhenrently dangerous and as woodworkers, it's a risk we all have to accept or else you quit woodworking... A leather apron would provide you very little protection against a flying knife. Don't forget a router bit can spin as fast as

20 000 rpm. Where talking here of a speed in the range of a few hundreds miles per hour. Bullets travel at a similar speed so if you get hit by a flying knife at max speed it's like being shot with a .38 caliber. Your leather apron won't do anything...

Cyberben

[Clint]

IMHO, now you're just being silly. I'm not going to do all the math again, but here's some sources, and their conclusion.

bit speed = ~60 mph at the tip for a 1" bit @ 20,000 rpm

From the rec.guns FAQ

velocity of a 38 special ranges from 1085 to 760 fps, depending on weight of the bullet. Works out to (velocity in f/s) f/s * 3600 seconds/hour / 5280 ft/mile = 739 mph to 518 mph.

Order of magnitude difference.

Another important measure is the amount of energy delivered. That same FAQ lists the bullet energy at 156 to 290 ft pounds. For the router bit, I'm going to pretend the largest fragment would be about the size of the bullet, but I'm just making that up cuz I'm lazy. Since the wood-working FAQ lists the kinetic energy as 1/2 * mass * velocity squared, and the only difference is the velocity of the two projectiles, the amount of energy of the bullet would be about 100 times greater. That gives the router bit 1.56 to 2.9 foot pounds of energy, which is less than a .177 caliber airgun.

Whew! Guess I shouldn't have taken today off. :) Net effect is I wouldn't want to get hit with either item, but I'd much rather be hit by the router bit pieces. Of course, this doesn't take into account the fact that the router bit pieces are probably rather sharp, rather than "bullet" shaped, but still...

Clint

[bf]

the leather apron would probably be a good idea (can't hurt). Routers are dangerous, no doubt. But, if it makes you feel any better, I had a chunk of carbide off a bit fly off and hit my arm. It was a pretty good cut, but it's not as if it put me in the hospital or anything. I did stop using cheap bits after that though :)