# ball bearing crushed in hydraulic press: why the explosion? **URL:** \ **Category:** Factual Questions\ **Created:** [July 8, 2016, 7:37pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420 "2016-07-08T19:37:34Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [July 8, 2016, 7:37pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/1 "2016-07-08T19:37:34Z")
[Video here;](https://www.youtube.com/watch?v=NWySdXedUiY) fast-forward to 0:40. A single ball bearing is crushed by a hydraulic press. After briefly distorting, it shatters and generates a whole lot of sparks. Why the sparks? ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [July 8, 2016, 7:44pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/2 "2016-07-08T19:44:49Z")
Iron is pyrophoric in small enough particles; I’d wager the ball bearing was hardened steel (look what it did to the press ram!) and with how rapidly it shattered, enough heat was generated to ignite the particles of steel as they scattered. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 8, 2016, 7:45pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/3 "2016-07-08T19:45:06Z")
Well, the bearing is very hard. It acts like a spring, storing up all that energy until it fails catastrophically, and all that stored energy is released as heat. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [July 8, 2016, 7:45pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/4 "2016-07-08T19:45:17Z")
The metal fragments are heated by the compression. ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [July 9, 2016, 5:19am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/5 "2016-07-09T05:19:50Z")
Take a piece of sheet metal and bend it back and forth. Before it breaks it will get hot. The ball bearing hard heat treated steel. Distorting the ball creates a lot of heat. When it torn apart creates more heat. ---
**Author:** ![thirdname](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@thirdname](https://boards.straightdope.com/u/thirdname)\ **Post date:** [July 9, 2016, 8:53am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/6 "2016-07-09T08:53:25Z")
If it couldn’t explode, how else would the ball bearing be able to at-tack at any time? ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [July 9, 2016, 9:58am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/7 "2016-07-09T09:58:19Z")
> [@Machine\_Elf](#): > > Why the sparks? cementite in the crystal structure. F3C , Cementite, is very flammable. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 9, 2016, 11:31am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/8 "2016-07-09T11:31:25Z")
In addition to everything else, the metal heated by pressure is shattering into tiny particles with a large surface area to volume ratio which allows rapid oxidation. Remember that iron ‘burns’ at very cold temperatures when it rusts, increasing temperature and the surface to volume area allows rapid burning. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [July 9, 2016, 11:31am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/9 "2016-07-09T11:31:50Z")
> [@Isilder](#): > > cementite in the crystal structure. > F3C , Cementite, is very flammable. That’s Fe[sub]3[/sub]C, better known as iron carbide. F is the symbol for fluorine, which is bad news if it gets in your hydraulic press. I don’t know if there would be enough iron carbide in a steel ball to explain all the sparking. I think it’s mostly due to heat caused by the compression and shattering, as mentioned above. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [July 10, 2016, 7:12am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/10 "2016-07-10T07:12:17Z")
> [@friedo](#): > > I don’t know if there would be enough iron carbide in a steel ball to explain all the sparking. I looked it up due to this question… Obviously I meant Fe3C . Its present in pearlite, 8%. Its the layers of cementite (iron carbide, Fe3C ) and ferrite that makes it look pearly… Does fencing wire spark ? nope. Pure Fe metal, or highly annealed steel, contains no pearlite… and doesn’t spark. The iron carbide will have a lower flash point … its the easiest to get to ignite. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [July 10, 2016, 7:21am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/11 "2016-07-10T07:21:06Z")
> [@friedo](#): > > I don’t know if there would be enough iron carbide in a steel ball to explain all the sparking. I looked it up due to this question… Obviously I meant Fe3C . Its present in pearlite, 8%. Its the layers of cementite (iron carbide, Fe3C ) and ferrite that makes it look pearly… Does fencing wire spark ? nope. Pure Fe metal, or highly annealed steel, contains no pearlite… and doesn’t spark. The iron carbide will have a lower flash point … its the easiest to get to ignite. ---
**Author:** ![The\_Niply\_Elder](https://avatars.discourse-cdn.com/v4/letter/t/8e8cbc/32.png) [@The\_Niply\_Elder](https://boards.straightdope.com/u/The_Niply_Elder)\ **Post date:** [July 10, 2016, 8:16am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/12 "2016-07-10T08:16:18Z")
In addition to everything that’s been said, I want to ask where is that dudes accent from? It’s like a mix between a Russian and Spanish. Also, at the moment of shattering the pieces attain near the melting point of iron, much like a milling machine cutting metal and chips flying off. ---
**Author:** ![mbh](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@mbh](https://boards.straightdope.com/u/mbh)\ **Post date:** [July 10, 2016, 8:26am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/13 "2016-07-10T08:26:20Z")
> [@The\_Niply\_Elder](#): > > In addition to everything that’s been said, I want to ask where is that dudes accent from? It’s like a mix between a Russian and Spanish. Scandinavia. In other videos, he makes occasional references to Sweden and Finland. ---
**Author:** ![thirdname](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@thirdname](https://boards.straightdope.com/u/thirdname)\ **Post date:** [July 10, 2016, 8:26am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/14 "2016-07-10T08:26:32Z")
Finland. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 10, 2016, 8:41pm UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/15 "2016-07-10T20:41:38Z")
Is Finland Scandanavia? Real question. ---
**Author:** ![Mighty\_Girl](https://avatars.discourse-cdn.com/v4/letter/m/7bcc69/32.png) [@Mighty\_Girl](https://boards.straightdope.com/u/Mighty_Girl)\ **Post date:** [July 11, 2016, 1:58am UTC](https://boards.straightdope.com/t/ball-bearing-crushed-in-hydraulic-press-why-the-explosion/759420/16 "2016-07-11T01:58:18Z")
English sounds different with different Scandinavian accents. Finns aren’t considered Scandinavians, though it’s a Nordic country. At least from most Scandinavians and Finns I’ve heard of. WWII helped none with that sentiment.