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Hammer to Hammer

comments (21) August 20th, 2009 in Blogs
Ed_Pirnik Ed_Pirnik, producer

Video Length: 1:33
Produced by: Ed Pirnik, Mike Dobsevage

For a few years now, one of my guilty pleasures has been to plop down on the couch with a frosty beer, flip on the TV and tune in to Mythbusters. I simply can't get my head around the fact that these folks have been able to find someone to pay them for having fun. God, what I'd give to be able to hang out in a shop all day and invent any number of hair-brained devices aimed at testing the abusrd, the little-known, and the just plain crazy!

Drum roll please . . . . Ladies and gentleman: my day has finally arrived.

A recent post on the dangers of striking two hammers (see photo above) together by the folks at our sister publication, Fine Woodworking, generated a great deal of commentary. Among the gruesome true-life stories sent to us by readers were these three gems:

". . . my final strike caused the hammer head to EXPLODE, leaving a marble size pellet missing from the hammer head and a corresponding hole in my leather apron, my denim jeans and my kneecap."

". . . when I was a youngster I too struck two hardened surfaces together, a sledgehammer onto an ax, trying to split an ornery piece of firewood. The result was a large razor sharp chip deeply slicing my leg."

"When I was 12 years old I built my first tree-house. At the end of one workday I was walking up the driveway to my house in Atlanta carrying 2 hammers and banging the heads together in a typically vigorous 12 year old way. Suddenly a searing pain erupted in my left pointer finger knuckle as a hot piece of hammer-head shrapnel flew into my hand."

I decided this would be the perfect opportunity to build my own hammer-smashing rig and let the chips fly. Now, before some folks begin firing off emails to me regarding the nature of my rig, please note that this wasn't meant to be a strictly controlled scientific test. I simply wanted to bang the heck out of a couple of hammers and record the results.

And what happened? Well, you'll have to watch the video to find out. As for me, my mythbusting days are over. It's time to get back to the nuts-and-bolts of Fine Homebuilding, but rest-assured, if there's another crazy rig to be built, I'll be there.


For more on hammer tech, visit our tool guide entry on titanium vs. steel.

posted in: Blogs, safety, hammer

Comments (21)

Coffered Coffered writes: Your benchtest did not result in either hammer shattering because your rig could not develop the high energy needed to shear dense forged steel. Your rig failed to ascribe to the general principle that mass times speed equals force. A heavy mass traveling at a slow speed won't get the job done. Give your good ole' human arm some credit...the energy accumulated via swinging a hammer with your arm is waaaaaaay higher than swinging that cumbersome wooden rig because your arm is swinging the hammer with a much higher head speed, plus your arm represents a good 20+lbs of mass behind it. I am going to estimate your rig's maximum speed at maybe 30mph, while a good estimate of the head speed of your arm-swung hammer would be in the vicinity of 60mph+. When you swing a hammer your arm speed is only about 30mph; but, the whipping motion of your wrist accelerates the hammer head exponentially, thereby causing head speed in excess of 60mph that regularly drives 12penny nails in one stroke by experienced framers. I would have liked to have seen you do the shatter test swinging the hammer with your arm. You could have worn flexible kevlar arm protectors available cheap at safety clothing outlets and used plexiglass sheeting to protect the rest of your body and swung away. I bet you could have exploded that hammer in less than a hundred swings. You could use that Mythbusters test firing gel to measure the penetration if you wanted to kick out a hundred bucks or so for the gel.
Someone wrote that forged hammers resist shattering. WRONG! Forged hammers are the ones that explode with the most lethality. A forged hammer's molecules are so densely packed that it is difficult to separate them. But the strength of their density is potential energy waiting to explode violently when acted upon with sufficient energy. A forged hammer is so hard it shatters relatively easily. Forged gearsets in automobiles are treated to bend slightly under the immense forces of a hard launch because the very strength in forging that they need to handle extreme stresses is the cause of them exploding like a hand grenade if not alloyed with components that modify their tensile properties to allow them to flex a bit. I would be surprised if these tensile softening components are included in the mix when they are selling a $30.00 hammer.
I have hit cat's paws a bazillion times and never caused shattering because the paw is not forged. It is soft metal that is not prone to shattering. I have also hit forged hammer to forged hammer many times without a shattering. I was lucky. It was only when I hit a forged hammer to a forged automotive spindle that I ended up in the hospital getting a shard of spindle pulled out of my forehead where it stopped only after contacting my skull. The spindle end was relatively small, and it was threaded, thereby giving it an avenue to shear and ricochet off the backing plate at an untold rate of speed directly into my head. A hammer, by virtue of its large head, is not prone to shearing. So it would be difficult to cause a failure. But, I am sure it can happen...and with possibly dangerous consequences. Someone also wrote about a mushroomed hammer having a greater propensity to shatter. I haven't seen a forged hammer mushroom appreciably, so I would have to assume this was a cheap Harry Homeowner hammer. One should have the presence of mind to throw away any tool that has been used beyond a safe condition. Noone would be surprised if a mushroomed hammer blew apart.
It isn't a perfect world, as a professional framer I often find a need to swing hammer against hammer, albeit reluctantly. Very few framers wear eye protection. Some find it uncomfortable to wear eye protection forty hours a week. I tell the guys who insist they don't want to wear goggles that they might as well leave their eyes wide open to at least save their eyelid when that shard is coming at them at probably upwards of a thousand feet per second...nuff said
Posted: 4:53 pm on October 7th

ShaneDugas ShaneDugas writes: Never hit two hammers together!!! My dad currently has only 5-10% of his vision left in one of his eyes as a result of this exact thing. One of the teeth on a waffle head hammer chipped off and flew into his eye.
Posted: 9:23 pm on August 27th

dmkatz01 dmkatz01 writes: I agree with your final statement, "My eyes are too important to me to tempt fate".
Everyone should wear quality safety glasses when working in the shop.
The only reason you didn't generate a chip is that your hammers looked to be in fairly good (perhaps fairly new) condition.
As a safety professional, I've pulled many a mushroomed hammer head out of the hands of production and maintenance employees. This is the most likely source of a chip (although it doesn't have to be mushroomed, just work hardened until it is brittle).

Take care of yourselves.
Posted: 9:05 pm on August 26th

Bark Bark writes: As a kid I was at the nieghbors building a go-cart. The dad in charge was trying to remove a bearing from a wheel and placed the point of a geologist hammer on the bearing and struck the square end with a ballpean hammer. Us kids were amazed at the stream of blood spouting from his hand 2 feet in the air. A chip had come off the geologist hammer and entered his hand between the thumb and index finger clipping the artery. We all learned something that day, right tool for the job means everything, plus the magic of metalurgy. I liked the tip about cheap chisels and punches, I won't use one with a mushroomed head either, a minute on the grinder seems a small price to pay for safety.
Posted: 10:25 am on August 26th

Cadabra Cadabra writes: Ed -
Between you and the Mythbusters I think you've both proved that metallurgy has everything to do with hammer safety. And, of course the drop forging process is the other key. Actually, the two go hand-in-hand. Yes indeed, Metalsguy got it right.

The cheap steel hammers of yesteryear are where the lore, legends and horror stories are made. Millions of them still linger-on in garages, basement tool benches, and Dad's old tool box. Just toss the old dog out if you're not certain of its pedigree! Buy a well made hammer that is drop forged and you will most likely never have a problem with it chipping or shattering. None the less (all the more, even so) just never strike any hardened steel or brittle object with a hammer. Forgo the cheap punches and chisels at Harbor Freight; they are dangerous.

Reading the comments with stories of eye shrapnel are bone-chilling. Wearing safety glasses is a small inconvenience to save your vision. Just wear a patch over one eye for a full day. After that, you will gladly wear safety glasses over both eyes for the rest of your days at work.
Posted: 4:14 pm on August 25th

Ed_Pirnik Ed_Pirnik writes: Metalsguy: "Great Video, A cross between a mattress advertisement and some of the shop teachers . . . " Maybe I should have gone for a more "Billy Mays" look. LOL
Posted: 1:14 pm on August 25th

Ed_Pirnik Ed_Pirnik writes: gonuts: I'm seeing the Stiletto TIBAR 16" going for $209. It's anything but cheap!

And as I said in the video - I've seen PLENTY of folks over the years banging on a hammer head in order to coax the claw under a stubborn nail head.

Posted: 1:13 pm on August 25th

lochness lochness writes: Who is stupid enough to hit to hammers together. This is darwins theory in full effect. If you ask to borrow someones hammer, what he doing while your beating on it. Standing there wasting time? Must be an east coast thing, just like sidewinders
Posted: 12:35 pm on August 25th

gonuts gonuts writes: What about Ti hammers? Are the resistant to chipping?
They make Ti cats paws also, so does that mean it is fine to drive away on them.
If the cats paw weighs half of the steel one I would be more likely to have one in my bags. That is if they didn't cost two hours wages for a consumable tool.

Posted: 10:25 am on August 25th

Ed_Pirnik Ed_Pirnik writes: Metalsguy: I could have used you when setting this rig up!

Chemdad: Tell me about it! I once quit a framing crew up in Rochester, New York after I discovered that one of the guys sheathing roofs with me was a drug addict. Never safe to be tossin' around sheets of 4x8 with someone who is high as a kite. Walked off the job that afternoon and didn't look back.

I think that in the end, there are simply so many variables involved, that actually reproducing it can be touch. Casting, forging methods, etc, are handled differently in different countries. Who knows what kind of oversight foreign manufacturing firms have in place. Looking back, I don't think it's so surprising that it didn't work out the way I had hoped! But like I said, I've heard too many stories - from you folks and those over at Fine Woodworking - to ignore the phenomenon!

Cheers all,


Posted: 9:39 am on August 25th

Eyeguys Eyeguys writes: try a nasty old rusty hammer. As the Ophthalmologist on-call, I can tell you, metal to metal impacts can send tiny sharp fragments right through your contact lens, cornea, anterior chamber, lens, vitreous, and become imbed into your retina and all you may feel is a transient sharp pain. All your ER doctor may find wrong is a corneal abrasion. As a weekend remodeler, I hammer away, but use safety glasses like my vision dependson it.
Posted: 1:15 am on August 25th

DVanditmars DVanditmars writes: The specific metallurgy of the hammer(s) used will determine if there will be chips flying or not.
Posted: 1:09 am on August 25th

Sharkbait Sharkbait writes: Why would you not just use a catspaw? There is a reason the are made of a soft untempered metal. I've see the aftermath of this kind of stupidity. Working on setting trusses with another guy. He borrowed someone else's hammer to help remove a truss spacer and bam! A piece the size of a .22 shot into his forearm. I was warned against this by my dad growing up. The right tool for the job.
Posted: 9:47 pm on August 24th

BldrMtnMn BldrMtnMn writes: I know that many think that the dangers of banging hammer heads together is minimal, but my life experience says otherwise. At age ten I was engaged in just such an activity while on a school sleepover field trip. I was tearing boards of with one hammer facing up, with the claw under the board and striking vigorously with another. I'm not sure how many strikes, but I would say a good ten minutes of this activity caused one of the hammers to shatter sending shards of steel into my left eye. Three of the shards remain to this day in my eye, they got two on the initial operation. I'm 51 now, so the accident was some 40 years ago, but the sound of two hammers being struck together, still raise the hairs on the back of my neck. I learned the hard way, I would recommend finding a different method.
Posted: 8:19 pm on August 24th

toolmonger toolmonger writes: Mythbusters actually tested this theory and "proved" it wrong. They set up a rig similar to what Ed built and had the same results. It seems the difference in the "myths" and the experiments is repeated hits and indirect hits. As we all know, what is produced in a lab and what happens in the real world often do not match. I've also hit many hammers to hammers and have yet to pick up any schrapnel, but I'll probably remember to put on my glasses and gloves next time.
Posted: 6:51 pm on August 24th

psluss0822 psluss0822 writes: I dont see a big probelm hitting two hammers together expecially if your wearing safty glasses. I have done this a couple times when a pry bar was not arround and like the video nothing happened. Think about it, we hit nails, pry bars, other metal objects and sometimes concrete with hammers. They are made to take abuse!!!!
Posted: 4:44 pm on August 24th

montereybay20 montereybay20 writes: I also stupidly was using one hammer to hit another. A piece of shrapnel about an eight of an inch in diameter chipped off the edge of the hammer face and entered my wrist, embedding itself under the skin. It was superficial enough that I was able to use a utility knife to cut it out...I learned my lesson.
Posted: 4:42 pm on August 24th

chemdad chemdad writes: New house are being built all around me. NOBODY wears safety glasses. Forget the hammer heads. Those workers I see are in constant peril from their own negligence.
Posted: 3:40 pm on August 24th

Metalsguy Metalsguy writes: Great Video, A cross between a mattress advertisement and some of the shop teachers I've known. Try freezing both heads, freezing both heads entirely. Drop forged hammer heads give the advantage of the molecular structure of the metal to follow the shape of the head. This molecular pattern resembles wood grain and the Forging process takes advantage of it. The things to avoid are cast steel, cast iron, and machined steel ( hammers blanked from common stock (mild steel). Drop-forged heads are okay to be machined, so look for signs of forging. A good Hammer usually makes a good ringing sound ( when struck).
Posted: 3:25 pm on August 24th

Loadmaster Loadmaster writes: Back when I was a sixteen year old kid, I got a dumb idea. Out of boredom, I started playing with the tools we had in the shed; I decided to grab two hammers and started banging thm together. It wasn't too long, maybe a bout ten strokes or a bit more, when one chip flew off of one of the hammers and hit my arm, halfways up to my elbow.

Posted: 2:17 pm on August 24th

JFink JFink writes: Great video!!
Posted: 9:47 am on August 21st

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