# scary mishap today ...



## wquiles (Jun 4, 2010)

First of all, I am not hurt or anything, well, maybe just my pride as an apprentice machinist. And as embarrassing as it was, I rather share it in the open so that hopefully others don't make the same mistake I did ...

I am working on a project that required me to make some new 10mm screws, about 60mm long, with the very rare 1.0mm pitch. Since the screw is not going to get stress or any kind, I decided to use 12L leaded steel.

I had a long piece, and since I know I was going to have about 2 feet of overhang past the end of the spindle, I used my spider to center the piece as best as I could:







My initial operation was going to be a simple facing, so that I could drill a tiny centered, pilot hole, to use a live end while threading, as I wanted to thread the 2-3 screws all in one operation:






I used the lathe's momentary button, and it seems to be in OK balance, so I setup my tool, the AccuRite lubber, the lamps, the safety shield, etc. - nothing new. I then made the one mistake that caused all this problem. I started the lathe, at the high speed I had before, which was 1200 RPM.

Everything seemed fine for a about 10 seconds, while I moved the cutter to the piece of steel, then all of the sudden, all hell broke loose. The machine started vibrating a LOT, and right in front of my eyes the 1200 pound lathe started MOVING away from me!. It took me a second or two to realize oh crap (well, I mentally used a stronger word!), and I calmly told myself: stop the machine - turn it off. 

It all seem to happen in slow motion. It took me (what seem at the time) like an eternity to think what I am supposed to do to turn the lathe off. As soon as I realized my hand was near the ON/OFF lever, I turn the lathe off. And everything stopped quickly and nicely.

As I stepped back from the lathe, this is the first thing I saw:






and then, even more horrifying, I notice this:






Yup, the lathe vibrated about 4 inches away from me in the quick time it started vibrating and the time it took me to realize the problem and turn it off.

Here is the offending piece of steel (about 4 foot long):






I was very calm, which surprised me a lot. I was also not hurt, at least not physically. And by virtue of standing in the right place, the safe place to be in a lathe, to the right of the chuck, I was never in danger of getting hit by the now-bent-piece of steel, which just a few seconds ago was flipping around at 1200 RPMs. Yup, I got lucky today.

Of course, after reflecting on what went wrong (and mental pictures of how bad could it been), I noted the three very important lessons for future work:
- don't have that much over hang - EVER!
- start at much, much slower speeds!
- next time keep the foot close to the lathe brake - just in case!

Once I reflected on those lessons, I reposition the lathe:






Re aligned the lathe with my Starrett level:






Checked everything on the lathe, once over, making sure everything was tight. I then cut the piece of leaded steel so that the whole piece was inside the spindle, and proceeded to continue on the job, of course, at a more reasonable 500 rpm's:






That is all. Please remember my mishap today, and hopefully you will learn from it, just as I did.


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## Illum (Jun 4, 2010)

I'm not a machinist but I cringed when I read "and right in front of my eyes the 1200 pound lathe started MOVING away from me!"


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## ninemm (Jun 4, 2010)

That's pretty nuts. Glad you didn't get hurt! Thanks for sharing, hopefully others won't make the same mistake.


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## wquiles (Jun 4, 2010)

Illum said:


> I'm not a machinist but I cringed when I read "and right in front of my eyes the 1200 pound lathe started MOVING away from me!"


Yup. It was definitely quite a sight. I did not expected that the lathe had travel that much, until I looked down and saw the old marks against the final resting position.



ninemm said:


> That's pretty nuts. Glad you didn't get hurt! Thanks for sharing, hopefully others won't make the same mistake.


Thank you. I know I got lucky today. 

If my mistake and me sharing it helps prevent this to at least one person out there, it was worth the embarrassing feeling I had in sharing this stupid mistake openly.


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## saabluster (Jun 4, 2010)

As soon as I saw that first shot I knew what had happened. Funny how the brain just skips town sometimes. I am soo glad you didn't get hurt. It blows my mind to think that bar could move the lathe. Hey maybe that would be an easy way to move it around from now on. Just stick that bar back in, crank the ol lathe up and push it where you want it.


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## Norm (Jun 4, 2010)

Lucky it wasn't a bit longer it would have been beating your BMW on the bonnet 
Norm


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## Chauncey Gardner (Jun 5, 2010)

Very scary. I'd check the lathe out very carefully also.

That kind of force with the out of balance weight at that rpm.....well, you saw how far it moved the 1,200 lb lathe.

Your description of the slow mo the brain does under extreme stress (much like what happens before serious physical trauma) was enough to make me squirm around a bit.

Glad you are ok, but that was very nearly something very bad.

Just a tiny bit of sag from your bar stock would cause this to happen given the length of overhang & rotational speed.

Don't even want to think what your leg (or arm) would have looked like if you had moved, slipped or gotten too curious...

Good post. It's amazing sometimes in retrospect how we avoid getting wrecked (or do anyway & see it coming in super-slo-mo) & look at what we did & say, "what was I thinking?".


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## Th232 (Jun 5, 2010)

saabluster said:


> As soon as I saw that first shot I knew what had happened.



+1. Also glad the car wasn't damaged. Bit hard to tell with that 3rd pic, how far was the end of the bar from the car?


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## Per-Sev (Jun 5, 2010)

I was a machinist for 16 years and I have never seen anything like that before. You said you used 12L steel I take it that is a very soft steel. I am glad you are still here to tell us about this I guess it had more run out then you thought. I have had it bang around inside the spindle but I ran a 24" dia swing lathe and could turn up to 26'' dia using a boring bar in the front of the tool rest.


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## gadget_lover (Jun 5, 2010)

Before I read the first line I saw that picture and knew the majority of the story. Knowing the size of your lathe I knew that long, thick stick-o-steel there was just waiting to become a wrecking bar.

Boy, are you lucky!

Thanks for sharing.

Dan


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## precisionworks (Jun 5, 2010)

> As soon as I saw that first shot I knew what had happened.


+1

That's pretty common, I did the same thing some years back. If your lathe has a "jog" button, that can help avoid disaster - I always jog the spindle first before starting any new op to make sure all the settings are correct, that the part is centered, etc. It adds a few seconds to the process but quickly indicates an incorrect setup.



> check the lathe out very carefully also


+1

There's a pretty good chance that you'll have to reset the Set-Tru screws, especially if the vibration caused any of them to back out.

Not a bad time to check the bearing preload. I believe your machine has a 1.5" spindle bore, if so you'll need a 24" length of 1.5" solid round stock, although heavy walled tube like Schedule 80 will also work. Remove the chuck & insert 12" of the bar into the headstock. Bring a dial test indicator into contact with the spindle nose & pull hard on the end of the bar. The indicator should show at least .0005" movement, but no more than .0010". Repeat the test by pushing hard, readings should be the same. Adjust preload if needed following the well written Chinglish instructions


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## TorchBoy (Jun 5, 2010)

I'm not a machinist either, and when I saw that first photo my only thought was "I hope he's not going to spin it quickly." I guess quick is relative. I've done similar things with a masonry drill bit (or two). Thanks for a good write-up and the lesson we can learn from it.


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## Tom Anderson (Jun 5, 2010)

Scary stuff!

Thankfully, you weren't injured!


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## wquiles (Jun 5, 2010)

precisionworks said:


> If your lathe has a "jog" button, that can help avoid disaster - I always jog the spindle first before starting any new op to make sure all the settings are correct, that the part is centered, etc. It adds a few seconds to the process but quickly indicates an incorrect setup.


My lathe has a jog button, and I do use it a lot. I used it on this job as well, and for the 2-3 seconds of the jog, everything was fine. It was not after the 10+ seconds of actual running that all hell broke loose. I guess that once I started to move the carriage, cutter, etc., everything aligned "just right" for the harmonic frequency to start making the shake. Once it started, it only got worst - again, it all happened very quickly. Of course, if I would had started much slower ...

Definitely a mistake I will never do again :thumbsup:





precisionworks said:


> There's a pretty good chance that you'll have to reset the Set-Tru screws, especially if the vibration caused any of them to back out.
> 
> Not a bad time to check the bearing preload. I believe your machine has a 1.5" spindle bore, if so you'll need a 24" length of 1.5" solid round stock, although heavy walled tube like Schedule 80 will also work. Remove the chuck & insert 12" of the bar into the headstock. Bring a dial test indicator into contact with the spindle nose & pull hard on the end of the bar. The indicator should show at least .0005" movement, but no more than .0010". Repeat the test by pushing hard, readings should be the same. Adjust preload if needed following the well written Chinglish instructions



Ever since I saw how you adjusted your bearing pre-load I have been wanting to check it, and since I also own one of those infrared temp sensors, this is the perfect "excuse" to do it.

The other thing I must do is to find a way to mount the lathe in a more stable/solid position. I have never liked how top heavy my setup is, and I have always found the base/feet too narrow for my taste. Myself and others with these 12x36 size lathes have commented in some of the newsgroups that these lathes could really benefit from a much heavier/wider base, so this "incident" just re-affirms this fact. There is just too much flex on those mounting cabinets - I definitely need something more sturdy and bottom heavy to get a more solid setup.


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## F250XLT (Jun 5, 2010)

Scary experience indeed, glad you are okay. I also applaud you decision to post it here, I am sure it will help educate aspiring machinists.


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## Illum (Jun 5, 2010)

F250XLT said:


> Scary experience indeed, glad you are okay. I also applaud you decision to post it here, I am sure it will help educate aspiring machinists.



makes me wonder how well you could vent a garage if you mount a propeller in the chuck....::green:

being that close to the car if you had been hesitant for a couple seconds longer there could have been a hefty scratch near the tire well
could the motor assembly be damaged through such an unbalanced load?


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## KC2IXE (Jun 5, 2010)

saabluster said:


> As soon as I saw that first shot I knew what had happened....snip...



Yep - saw the picture, first thought was - Oh, he didn't

BTDT, most of us probably have. No harm, no foul in this case. Now you need to get some outside supports


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## gadget_lover (Jun 5, 2010)

KC2IXE said:


> Yep - saw the picture, first thought was - Oh, he didn't
> 
> BTDT, most of us probably have. No harm, no foul in this case. Now you need to get some outside supports



I was going to mention that, but figured it might encourage bad behavior.

Here's my understanding;

The idea behind outboard support is that it lessens the oscillations to the point where the rod never gets far enough off center to allow centrifugal force to overcome the stiffness. The further off center, the faster it is moving. Moving faster = more force. More force = more deflection = moving faster.

If you constrain it in any two planes it will not be able to continue that cycle. 

I hope that is accurate enough for general understanding.

Daniel


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## HarryN (Jun 5, 2010)

One way to improve the hold down is to bolt it to the floor. The normal method is to drill some holes into the concrete through a convenient location in the base, and epoxy some all thread into the concrete. A few nuts and lock washers and you are finished.

This is used all of the time in earthquake prone areas.


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## KC2IXE (Jun 5, 2010)

actually, I find that for a stock stand, a PIPE the same ID as you spindle thru on a stand - actually a couple of them works fine - slide the stock through


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## precisionworks (Jun 5, 2010)

> One way to improve the hold down is to bolt it to the floor.


+1

If you extend the base you'll end up tripping on the extensions - at least I did. Harry's method is the way millwrights have installed heavy machinery for the past couple of hundred years, and is still the preferred method today.

You can either epoxy all thread into the concrete or you can install Red Head Trubolt wedge anchors - the people at the hardware store may not carry Red Heads & will try to sub something else, but nothing holds as well as a Red Head Trubolt

http://www.itwredhead.com/trubolt.asp

Easy to install with a hammerdrill & a carbide tipped bit, and both are available at rental locations nationwide. The "secret" to the thread anchors is that you first level the lathe & then use the thread anchor to pull down against the leveling pad. Done that way, the machine will never move again & it stays in level much longer.


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## wquiles (Jun 5, 2010)

precisionworks said:


> The "secret" to the thread anchors is that you first level the lathe & then use the thread anchor to pull down against the leveling pad. Done that way, the machine will never move again & it stays in level much longer.


Sounds like something to try, but remember I am highly visual - I don't quite follow you on this - what do you mean by still using a leveling pad? Can you please expand on this?


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## precisionworks (Jun 5, 2010)

Some machines, like mine, have two holes at each mounting location. If your has only one hole, a second hole is drilled next to the first one. The second hole is the one that the threaded anchor occupies, and when the nut is tightened on the threaded anchor it pulls against the leveling mount.


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## fyrstormer (Jun 5, 2010)

Man, I'm not even a machinist and as soon as I saw the un-secured end of that metal rod I thought "oh no, he started spinning it and it got off-balance and bent to the side." Done that on a Dremel a few times, and it's disconcerting even at that small of a scale. I can only imagine what it must be like to have essentially a piece of steel re-bar whipping around in front of your face like that. Glad you didn't get hit by it, or this thread would've been very different than it is.


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## wquiles (Jun 6, 2010)

precisionworks said:


> (snip pic)
> 
> Some machines, like mine, have two holes at each mounting location. If your has only one hole, a second hole is drilled next to the first one. The second hole is the one that the threaded anchor occupies, and when the nut is tightened on the threaded anchor it pulls against the leveling mount.



Awesome - after seeing the picture I get it - thanks 

Will


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## saabluster (Jun 6, 2010)

Hey Will if you need some help drilling those holes let me know. I have a hammerdrill that I used when I ran my sign company. I've used concrete anchors quite a bit.


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## StrikerDown (Jun 6, 2010)

I know Texans pride themselves on doing things BIG... but really, a 1200 lb weed eater?

 Live and learn, emphasis on the LIVE part! Glad you're okay.


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## wquiles (Jun 6, 2010)

saabluster said:


> Hey Will if you need some help drilling those holes let me know. I have a hammerdrill that I used when I ran my sign company. I've used concrete anchors quite a bit.


Thanks much Michael. My next door neighbor has one, so I am set 




StrikerDown said:


> I know Texans pride themselves on doing things BIG... but really, a 1200 lb weed eater?
> 
> Live and learn, emphasis on the LIVE part! Glad you're okay.


Thanks Ray


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## Rothrandir (Jun 6, 2010)

A shop I used to work at had that happen with a 12,000lb CNC lathe before I started working there. It moved far enough to disconnect it's own power. By all reports it was very, very loud.

Then there was the story I heard elsewhere about machinist A asking machinist B to grease his hands up and support the end of the bar while doing a real quick turning job. Machinist A survived.


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## cmacclel (Jun 6, 2010)

KC2IXE said:


> Yep - saw the picture, first thought was - Oh, he didn't


 

My thoughts exactly  Glad you didn't beat up yourself or BMW. The most I let something hang out is maybe 1 foot so that would never happen. I saw the same thing happen first hand 10 years ago at work. One of the inexperienced machinists loaded in a 6ft piece of 1/4 6061 aluminum and turned the machine on at 937rpm (Leblond Lathe) the 1/4 rod tore the collet closer box off the tail end of the machine! while making everyone there crap their pants!

Mac


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## Alan B (Jun 6, 2010)

Thanks for sharing this, Will. Great photos and story. Pretty scary.

Makes me really glad I have the variable speed setup, always start slow to verify things! (Though this looked scary even before starting to me).

Time for the VFD!


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## wquiles (Jun 6, 2010)

Alan B said:


> Time for the VFD!


I got the 5HP motor already - once I get enough money saved I will be buying the VFD and Braking resistor


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## TorchBoy (Jun 7, 2010)

Rothrandir said:


> Then there was *the story I heard elsewhere* about machinist A asking machinist B to grease his hands up and support the end of the bar while doing a real quick turning job. Machinist A survived.


I heard somewhere that was an urban myth. Pics or it didn't happen.



cmacclel said:


> The most I let something hang out is maybe 1 foot so that would never happen.


Spin a 1 foot overhang fast enough and wouldn't it would bend off centre too?


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## Torque1st (Jun 7, 2010)

I saw that 1st pic also and went Oh Sh--! 

For weight and mass consider filling the base with concrete or some of the newer materials for machine bases. There are articles and discussions over on PM about machine bases and filler materials.




KC2IXE said:


> actually, I find that for a stock stand, a PIPE the same ID as you spindle thru on a stand - actually a couple of them works fine - slide the stock through


That works and a lot of screw machines etc use that method. The roller stock supports work also.




TorchBoy said:


> Spin a 1 foot overhang fast enough and wouldn't it would bend off centre too?



Yes it will. It all depends on diameter and material.


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## wquiles (Jun 7, 2010)

Torque1st said:


> For weight and mass consider filling the base with concrete or some of the newer materials for machine bases. There are articles and discussions over on PM about machine bases and filler materials.



I have been thinking about doing both, not only bolting the lathe down, but also filling the two metal cabinets with something "heavy". Besides concrete, what other "filler" can I use to give it more weight? Any links to those discussions over on PM?


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## Torque1st (Jun 7, 2010)

If you search on; concrete machine base you will find many articles. Here is one to start with that has other links:
http://www.practicalmachinist.com/vb/gunsmithing/concrete-lathe-stand-186625/

another:
http://www.practicalmachinist.com/v...machine-tool-bed-casting-ideas-please-154076/


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## wquiles (Jun 7, 2010)

Cool - thanks much for the links


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## KC2IXE (Jun 7, 2010)

another thing you can do is "grout in" the machines - level the machine, preferably as close to the floor as possible, and pack in machinery grout under the legs/stands whatever, and wait for it to cure


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## HarryN (Jun 7, 2010)

wquiles said:


> I have been thinking about doing both, not only bolting the lathe down, but also filling the two metal cabinets with something "heavy". Besides concrete, what other "filler" can I use to give it more weight? Any links to those discussions over on PM?



Hi, some people fill their machines with shredded scrap tire rubber. It is pretty available most places and helps dampen vibration. You can bag it up to make it easier to move around as needed.


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## chew socks (Jun 7, 2010)

First thing i wanted to do when i saw the opening picture was jump through the screen screaming NOOO!!

....cause im ashamed to admit that i once did this on a machine of equal size, i was worried it was going to tip over for a second.


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## precisionworks (Jun 7, 2010)

> I heard somewhere that was an urban myth. Pics or it didn't happen.


Here's one that did happen, according to the NIOSH Fatality Assessment ... note that the machine started to make banging sounds just before the part & fixture launched & killed the machinist:

http://www.cdc.gov/niosh/face/stateface/mn/97mn028.html


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## Wilmette (Jun 8, 2010)

wquiles, I'm glad you're okay. Thank you for posting.

I have a LeBlond 15x30 and a Bridgeport mill in my garage, both on those round steel machinery feet with the rubber pads that many people seem to be using. Your post, one from HarryN, and one from Precisionworks has me rethinking my "floating machine" strategy.

My LeBlond has 7 feet. I am thinking that the 4 outboard-most ones at the very least should be anchors.


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## wolfy (Jun 8, 2010)

Glad your OK.

Glad dad has a heavy cast iron base, on his old lathe, and its bolted into concrete. As machining is a hobby for me, this is good lesson not to be learned the hard way.


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## Bimmerboy (Jun 8, 2010)

That was a frightening story, Will.

The main thing is that you're OK. This may be embarassing, but it could've been a whole lot worse. As one who's had only minimal contact with you, I'm personally relieved that you're unharmed. Much as I feel what the Bimmer almost went through, it's nothing in comparison, and would only be about money. I believe you were lucky to escape without serious injury, and am glad you're able to share the experience.

If it's any consolation, I had an expensive, and potentially dangerous mishap yesterday that takes the cake for stupid. I mean... _truly_. You'll feel like a genius in comparison. I'll PM about it tomorrow, because tonight I'm drowning my sorrows over the bill.

For all readers... As the saying goes, "measure twice, cut once." Translated to any situation, it means *think* when you're doing something. And, when tired, distracted, or if you've had an emotional day (all three in my case), sometimes best not to do it at all.


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## unterhausen (Jun 9, 2010)

thanks for posting this story, I probably would have recreated it at some point


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## precisionworks (Jun 9, 2010)

> when tired, distracted, or if you've had an emotional day


+1

Little room for error, as most machine tools will keep going & going & going, even if you have some body part wrapped around the spindle


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## StrikerDown (Jun 9, 2010)

precisionworks said:


> Here's one that did happen, according to the NIOSH Fatality Assessment ... note that the machine started to make *banging sounds* just before the part & fixture launched & killed the machinist:
> 
> http://www.cdc.gov/niosh/face/stateface/mn/97mn028.html



The school of hard knocks can be unforgiving. 

Every time I think about Will's 1200 lb weed eater... 

This is just something you don't think about. I had a long piece of 3/8 rod hanging out the back of my old 7x10 and as I was slowly increasing the RPM it started to rockin... fortunately I had my hand on the speed control and shut it down quickly, but not before the rod got bent! Really glad you posted this. Even knowing it can happen you just don't think about how bad it can get.


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## jhanko (Jun 11, 2010)

Will,
Glad you are OK. That is all that matters. Thanks for posting it. Seeing things like this really make you think twice...


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## wquiles (Jun 11, 2010)

Thanks much for all of the good thoughts


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## stinky (Jun 11, 2010)

wquiles said:


> Thanks much for all of the good thoughts



It can be hard to share something embarrassing, but you give a tremendous gift when sharing your mistakes (also known as "experience") may save others from more dire consequences.

Thank you so much for posting this story.


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