Dust explosion

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Forget the dust collector the drill press is the villain here. To day while drilling a 8" deep 1" hole with a spade bit at high speed in oak, I had an explosion. I was about 3 1/2" deep into the hole when with a loud bang and what appeared to be a flash, dust went all over the shop. Blinded by a layer of sawdust covering my glasses and with the taste of burned oak (maybe from oak dust landing in my pipe) I groped for the off switch to the drill press. In shock I looked at my wood, which was hanging from the drill bit and it looked fine with out my glasses on, looked fine after I cleaned my glasses and set down for a minute too. Found some ash and smell of "smoke" in the hole I was drilling so it must have been a real dust explosion. So dust explosions do happen but maybe not in dust collectors.
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sweetsawdust (in LC9wg.11678$ snipped-for-privacy@bignews1.bellsouth.net) said:
| Forget the dust collector the drill press is the villain here. To | day while drilling a 8" deep 1" hole with a spade bit at high | speed in oak, I had an explosion. I was about 3 1/2" deep into the | hole when with a loud bang and what appeared to be a flash, dust | went all over the shop. Blinded by a layer of sawdust covering my | glasses and with the taste of burned oak (maybe from oak dust | landing in my pipe) I groped for the off switch to the drill press. | In shock I looked at my wood, which was hanging from the drill bit | and it looked fine with out my glasses on, looked fine after I | cleaned my glasses and set down for a minute too. Found some ash | and smell of "smoke" in the hole I was drilling so it must have | been a real dust explosion. So dust explosions do happen but maybe | not in dust collectors.
I dunno - might wanna load your pipe with something more stable... :-)
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto
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wrote:

Ha!...lol
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Nothing to do with your explosion but rather your pipe. My niece wanted to make something with her uncle one day and we went out to the shop. After deciding she wanted to make a nameplate for her dad's desk we got to work with the scroll saw. Unbenounced to me while I was doing some of the more difficult cuts for her she was scooping small pinches of white oak sawdust into my Savanelli. Man did that ever taste bad ewwww. She got a good giggle out of it though so I guess it was worth it. Puff

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Seems you have proven that if you try hard enough to do it wrong, something bad will happen.

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And how did I do it "wrong" If you have a better way please enlighten me. Speed may have been a little high but not that much for the cut in end grain, clamping was tight etc..

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If the temperature was high enough to cause ignition, speed was more than just a little high.

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Speed was a little fast but I was not getting any heat build up or charring on the other holes I had drilled. The bit was cool enough to hold with out doing more then causing discomfort after drilling and had time to cool (about 15 min) between holes.

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You mean, besides smoking in a woodshop?
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

If a woodworker speaks in a forest, and there's nobody there to hear him........will Doug Miller still correct him?
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On Fri, 21 Jul 2006 23:32:34 -0500, "sweetsawdust"

Does this answer your question?

Could you drill that by hand? No.
How much power is behind your drill press ? Few hundred watts?
Now assume it's 90% efficient (it isn't) and half of that waste is going into heat. So that's the heat output of a reasonable size soldering iron, sat in a closed-in hole full of flammable sawdust. What do you think is going to happen next?
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"sweetsawdust"

The smoke and screeching that proceeded it would have given most of us a clue bad things were about to happen.
Dave
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No dust, No screeching, Everything was going smoothly with no problems and then BANG it happened. I have performed this operation several times with no problems. This time was a bit different and exciting.

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On Fri, 21 Jul 2006 23:28:25 -0500, "sweetsawdust"

Is it possible there was something inside the wood you were drilling? Some piece of metal or something else that, not so much causing an explosion, but something that caught and caused a "kickback" so to speak? I know you indicate you smelled smoke and charring, but that is sometimes normal with high speeds and/or dull bits in hard woods.

+--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+
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The Mark & Juanita entity posted thusly:

Something in the wood could also cause a spark. I used to see occasional sparks from calcium inclusions when cutting teak. No idea if oak can have the same, though.
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Oleg Lego wrote:

Wood can grow around just about anything, including small stones, grains of sand and so on.
I have to wonder if there wasn't something like a blasing cap (OK, that would be too big but something like that) in the wood. A dust explosion will not leave charred wood in the hole.
Here's a really wild hypothesis: Concentrated NItric acid reacts with celluose to make an explosive (guncotton). If somebody splashed a little nitric acid on the tree many years ago then there might have been a little explosive spot in the wood. I wonder, if you spilled ammonium nitrate fertilizer on a tree, could it form an inclusion that would go bang fifty years later?
If you didn;t have a posting history, or this was April, I wouldn't believe the story.
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My own opinion is that the bit may have gotten dull, I had drilled several holes with it since I last sharpened it. This could account for the slight charring I found in the hole, but not enough to cause a fire ( no glowing embers or any thing, just a dark "stain" on the wood) or maybe a foreign object in the wood. What ever the cause was it was a first time in nearly 40+ years of playing with wood that I have ever had anything like this happen. I have had steam explosions from using a dull bit at too high of a speed and have brought up glowing embers from the same cause, but this was a first. Just one of those odd events that was worth a passing on for amusement and pondering. I will now go back to making a living drilling ( hopefully none exploding ) holes in wood.
For what it's worth I did have a live bee come out of a hole in a board I was cutting the other day, but that is another story.

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snipped-for-privacy@spamcop.net says...

a) HNO3 (nitric acid) would kill any live tree tissue it stayed in contact with for any significant amount of time -- want an example? Stick your finger or other appendage in a bottle of it, don't wash it off, wait a while. It might not kill the entire appendage, but it'll turn real yellow and hurt like hell!
b) NH4NO3 (ammonium nitrate) is not an explosive -- it is an oxidant. When combined with a fuel source (usually hydrocarbons of some sort) the mixture can be explosive under proper conditions. Is what you're suggesting that someone bored a hole in a tree, inserted a quantity of ammonium nitrate, had it encapsulated by the wood tissue rather than dissolve in the sap and kill the tree, and years later supply the oxidant for a dust explosion? I'd have to say, possible. But, then again, so is it possible for a sufficient number of monkeys continually banging on keyboards to have one of them finally pound out the entire textual contents of the Library of Congress!
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Tex wrote:

Sure, but most of the wood in a living tree IS dead tissue. Only the outermost layers are alive. A 'dead' spot on the bark will get encapsolated if it is not too big. If you splash a little nitric acid on the bark and convert a little of the bark to nitrocelluose that little spot will get incorporated int othe wood as the tree grows. I'm suggesting just a tiny spot, not the whole trunk.

Depends on the conditions. Google Texas City Texas harbor explosion.

No, I'm suggesting that it go onto the bark and was encapsolated into the tree the same way a stone or nail gets encapsulated, and over the years converted some of the celluose to nitrocelluose.
--

FF


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On 22 Jul 2006 06:03:05 -0700, snipped-for-privacy@spamcop.net wrote:

It also reacts with oak tannins to make a very noticeable black stain. You'd see this a long way off.
I don't use nitric acid on oak, because it's pointless. I can stain oak with much simpler chemistry. However I do use nitric acid stain on maple and a few other timbers, sometimes heating it too.
Besides which, nitrocellulose won't last through a winter outdoors.
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