View Full Version : I just scared the poop out of myself today.

08-27-2009, 09:20 AM
It's a fairly normal day here in the shop. The phone is a little slow and I'm setting up a new job in our CNC turning center. This part is a brass button about 3/4" dia.

I'm running this part from bar and using a bar puller to index the raw material through the lathe chuck for the next part. Once setup, it runs by itself.

This CNC program has 2 parts..a main and sub program. The sub program does all the machine work. The main program just keeps count of the number of parts and tells when a new bar of material is needed.

Late yesterday, I finished debugging the sub program and ran a small bucket full of buttons in a semi manual mode. Today, I was going to run it in full auto from the main program...so I wrote the code, down loaded it to the machine, jogged everything into position for the first time..it looked good..so I punched the run button and were were off to the races!

The first length of bar was pulled into the chuck, the spindle started...and in the blink of an eye, I knew something was wrong...but I was a fraction of a second behind the action while my brain was trying to process everything. Suddenly the shop exploded with a thunderous racket. Everything in the shop shook and rattled. The deafening roar reverberated through my guts as my brain tried to catch up with what was happening. Everything seemed to be in slow motion as the 5500 lb CNC lathe started jumping in the air and walking across the floor. Finally, my frantic hands found the E-stop and there was silence giving my brain some time to regain the split second delay and realize what just happened.

My main program came from another part that we make..I just cut and pasted a few lines of it into this new job. One of those line was a "G96" command which keeps the cutting tool at a constant surface speed regardless of the part's diameter. So as the part gets smaller in diameter the spindle speed gets faster so that the surface speed is the same. It's a neat feature for some applications...but not today!! not for this job, not when everything else is program differently..and not on Bar jobs with bar hanging out of the back of the spindle.

When the spindle started, it reved up to an un-godly speed. I had about 12" of bar sticking out of the back of the spindle which flung around from the centrifigal force, bent at 90 degrees and tore the bejeezus out of the machine's enclosure. I have no idea how fast the spindle got to...

I knew better than this!! Holy smokes..how did I let it happen. I dunno...my knees are still banging together and my hands are quivering on the key board.

In the end, there is no blood...no foul. Just a torn-up cabinet panel and a bent rod of brass.

I'm going home for the day.

Be safe in your shop!!


Jeff Pearce
08-27-2009, 09:26 AM
Glad no one got hurt and nothing was broken to bad...Take it easy....huh1

08-27-2009, 09:55 AM
wow...i bet that was a moment. it is amazing how quick things can go wrong and with a machine that size, it would be lethal. glad you didn't get hurt.

Bill Coye
08-27-2009, 06:29 PM
Wow Rob.

Glad everyones okay.

08-27-2009, 08:45 PM
Since youre ok, the shop isnt burnt down, and no one is crippled from flying rod,.. I think im safe in saying thats both terrifying ,and hysterical to read.lol
As my Pop used to say after something REALLY scary happened fast--"Shriveled yer peas there for a minute didnt it kid?"

08-28-2009, 04:50 AM
Damn. Glad you're okay!

08-28-2009, 12:35 PM
Glad you are right. Man that is scary.

08-28-2009, 04:51 PM
Brass had no class. If you are going to kill yourself, you should be doing it with with 416ss:D

RJ Martin
08-29-2009, 06:33 AM
Hi Rob: Glad you are OK. For the first 6 months with my new CNC mill, I was a nervous wreck. I still use the "single line of code" switch whenever I run a new program to make sure I don't crash it.

Anyway, you were smart to take the rest of the day off.

RJ Martin

08-30-2009, 10:34 AM
First of all I'm thankful no one was hurt but especially you my friend. I hate when those unforeseen things happen in the shop. Its usually always something we all know better about but kick ourselves over after it happens too. Of course its always bad to have something happen like this but man this sounds really be scary to have a big machine like that jumping about. Whew! I bet your heart was about to pound out of your chest! Every bad accident I've ever had has been when someone was in my shop with me and my focus was distracted. I can't even let the pets in there with me when I work usually. I had a cat jump up on my table when I was grinding a blade once and scared the daylights out of me. Of course I messed up the grind too! Its why I work alone now. I seem to do better with no distractions and when folks come by now I stop working until the visit is over. I nearly cut my finger off once from that so I feel for anyone that has a close call in their shop. I don't blame you at all for calling it a day after that. I do that too. Reassess the damage when you recover. Its about all you can do. Stay safe guys.


Nathan The Machinist
09-07-2009, 01:24 PM
I keep waiting for someone to invent a sphincter mounted E stop.

I have a mantra I repeat before I ever start a new program, and you'd be surprised how many times I've caught a screwup.

Is the fixture zeroed
Is the spindle zeroed
Are to tools zeroed

And I might add - am I in G96

I learned to turn without it, so I don't use it, but then again I'm an R-tard and I don't do production lathe work. But if I did I'm sure it would catch me. Hell, it has a 6K spindle but only a 3K chuck. :eek:

Oh, and in my shop, the first part gets run with all the overrides set at 50% and somebody has a finger on the little red button. Saves some excitement when you put in the wrong facemill etc.

Glad you're okay. Hope your bearings are okay. Have fun releveling your lathe.

Knife Crazied
09-07-2009, 03:45 PM
Sure glad you weren't hurt.