Explain glass breakers to me...

D

dillon_b12

Joined
Dec 23, 2009
Messages
242
I don't get it. I think it is safe to assume that, for most of the public, glass breakers will only be used in an emergency situation.

If you are already carrying a knife, why couldn't you just use the tip of the blade to break the glass? I realize this could damage the knife/blade, but if you are trapped in a burning car you probably won't care too much about the condition of your knife.

Now for LEOs(or firemen, EMTs, etc...), who may be need to break glass on a much more frequent basis, I can see the use. But for the average consumer, it doesn't make much sense to me.

Do actual purpose-built glass breakers perform better than the tip of a blade?
 
Tips can glance off and go who knows where, really not good to have something sharp with an edge glancing off anything near your head/neck. :eek:
 
I've never used the tip of the blade but even CHEAP CHEAP glass breakers will still bust glass up quite well.

Also most knives with glass breakers are LEO/MIL. (Microtechs and such).
 
I still think I would try it, if all I happened to have on me was a knife that didn't have a glass breaker, and my life was on the line.


Just to clarify, I mean that I don't understand knives with glass breakers. Not just glass breakers in general.
 
Stabing a window will result in a damaged blade and probably a sore hand as well. A dedicated glass breaker gives you more controle and is generally made of harder material (like a ceramic of some sort) than a blade would be so is more effective for task.
 
I think the tip of a knife might be able to break glass, but then again it could break or bend instead. There's also the risk of it glancing off (dangerous), hand slipping to the blade due to hitting a very hard object (dangerous), and lock failure (dangerous). Most people underestimate the hardness of automotive tempered glass. It is actually quite difficult to break.
 
glass breakers are typically much harder than the blade material, and even then the ones on knives dont work so well unless they are spring loaded. ceramics or carbide tips seem to be common.


vehicle windows are suprisingly difficult to break. and if you try one of these on the windshield, you'll just end up with a little hole (they don't shatter).
 
MORIMOTOM said:
glass breakers are typically much harder than the blade material, and even then the ones on knives dont work so well unless they are spring loaded. ceramics or carbide tips seem to be common.


vehicle windows are suprisingly difficult to break. and if you try one of these on the windshield, you'll just end up with a little hole (they don't shatter).
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I had a few hours of fun at a scrap yard not so long ago. I and a few friends tested out the glass breakers on the Umnumzaan, Microtech troodon, Surefire Mk2 pen, as well as things like spark plugs, rocks and the butt on knives like the ASH-1 and CRK Pacific.

Out of them all the ASH-1 and a thrown spark plug were the only things that broke a side window on the first try.

(The ASH-1 was used like a hammer with the knife secured in the sheath, not a hamer fist strike with the knife in hand).
 
The idea is you carry your knife on you most of the time, and should you be in a car wreck or witness one, you can use the glass breaker as a relatively safe tool to evac through a window or windshield. As long as it doesn't get in the way or affect ergonomics I don't care if they're there, but usually aren't a deciding factor when buying a blade...
 
Good luck getting through a windshield with anything short of a axe. Side tempered glass is not just hard to break its extremely hard to break. The tip of a knife would smash like clay upon impact to the glass and you would be even further up sh!?& creek without a paddle.

I personally feel they are a useless feature.
 
knifenut1013 said:
Good luck getting through a windshield with anything short of a axe. Side tempered glass is not just hard to break its extremely hard to break. The tip of a knife would smash like clay upon impact to the glass and you would be even further up sh!?& creek without a paddle.

I personally feel they are a useless feature.
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I was told that windshield and window glass will break with about 100 pounds per square inch of pressure-with a glass breaker it's about 4lbs of pressure you need to apply to get a window to shatter. If this is true, then it's a practical feature if applied correctly.
 
Glass is brittle but as hard as cutlery steel. Both are around 5.5 on the Mohs scale. What would happed if you rammed the tip of your knife into the side of another blade? Expect the same thing with glass. You could in theory break it with your knife tip, but expect to fold it. Take a look at the life hammer and other breakers with hardness similiar to knife steel. The inclusive angle is around 90 deg, not the 40-50 typical edge bevel or the more severe point angles. It's going to be near impossible to fold.
 
dillon_b12 said:
I still think I would try it, if all I happened to have on me was a knife that didn't have a glass breaker, and my life was on the line.


Just to clarify, I mean that I don't understand knives with glass breakers. Not just glass breakers in general.
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I'd rather try hammering with the butt end or with a closed folder rather than stabbing with the tip. Ever try stabbing something hard? I wouldn't want to do that if I had a choice, I've seen too many people with damaged tendons in their fingers because they thought it was easy. If your hand slides off the handle in to glassbreaker chances are you won't get injured. I can't say the same if you had a hard grip on the handle and your hand slides onto the sharp edge will still gripping hard.
 
MORIMOTOM said:
vehicle windows are suprisingly difficult to break. and if you try one of these on the windshield, you'll just end up with a little hole (they don't shatter).
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Laminated glass. You can shatter it, but the polymer in the center holds it together.

dwong said:
sometime it not easy to break the glass, some video on a spyderco tip
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That's the reason you're supposed to hit in in the corner. If you hit it in the center, the glass flexes and absorbes the energy of the impact.
 
Clang! said:
That's the reason you're supposed to hit in in the corner. If you hit it in the center, the glass flexes and absorbes the energy of the impact.
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Don't the newer windshields and windows have a mark somewhere in the corners where you're supposed to hit them if you need to break them?
 
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