What's your best crash / n00b mistake story?

[plasmator]

I'm a real n00b to CNC milling - just got my first machine. Last night, I was having issues trying to get anything to happen for me with some A36 steel. No combination of speeds and feeds seemed to work right at all. New tooling, shouldn't have been anything keeping me from making chips.

Then I noticed that the spindle wasn't running in the right direction.

A wire had come loose and apparently the spindle controller defaults to reverse(!). I completely torched a 1/4" HSS endmill (welded it to the part!) before I realized this.

Note to self: Don't machine while tired...

So what are your best stories? With as many combined years of expertise (or lack thereof) on this board, there's bound to be some good ones.

[christinandavid]

I have returned to a machine to witness red hot molten blobs of cobalt drill dripping back into the hole that it was presumed to be drilling.

Another good one was leaving a one off prototype mega-urgent job running overnight and returning in the morning to find that the cutter had pushed the job all over the place whilst it carried on attempting to cut it. Not good.

Then there was the time I rammed a long series 40mm endmill so hard into the table it split into two equal halves (the cutter that is) from end to end.

The funniest one I ever saw was a over-tall job on a VF4. The operator inadvertantly 'homed' the X-axis and sent the job crashing into the tool carousel. Managed to stifle my amusement until the table was gingerly jogged back and the whole tool change mechanism just dropped about 3", sagging grotesquely - I couldn't help p!ssing myself laughing by that point...

I am constantly surprised to find new ways of scrapping parts/breaking machines. An equally interesting idea for a thread would be 'fk ups I got away with...'

After many years of experience you can developed heightened senses and train your brain to filter out all other distractions - only last weekend on my morning break I was chatting away when I heard the sound from my machine 'change' and sprinted 100 yards, managing to rescue my cutter body after all the inserts had failed.

Will post more when I think of them, there's so many...

DP

Ha! Just thought of one! Same operator that stuffed the VF4 also tried to lift a trunnion rotary table off a VF9 without unclamping it from the machine bed! The machine (this is quite a large one) needed re-levelling afterwards - and the eyebolts were a little stretched...

[plasmator]

I find myself unfortunately replying to my own post...

Last night I learned the hard way to tighten the screws on my parallel port connector... It came partially loose, such that the X was still connected and driven, but everything else was not (including the spindle!). Needless to say, all hell broke loose and the 3/8" endmill snapped like a twig. Good thing I've been testing the machine with some cheap import tooling.

[christinandavid]

It's not too bad when you only have yourself to answer to. Only a few weeks ago I was setting a 40mm U-Drill in an eccentric holder. Got it cutting correct size, checking my little 20mm deep test hole. Set it going, drilling luvly. Next minute BANG! Drill has disappeared. Stop the machine to find what remained of the drill (the flatted bit of the shank) loose in the holder...it must have pulled out and tried to mill it's way over to the next hole position...now did I tighten it up after adjusting it? No way to know for sure but it don't look good and that's the only 40mm drill in the shop (long enough for this application). I have some explaining to do...

Never did find any other remains of that drill...seriously I didn't. I think it either atomised, or the titanic forces involved in the collision created a warp in spacetime and the broken drill fell into a temporal vortex/wormhole and is maybe floating around somewhere in deep space. We'll never know.

See you in the next installment.

DP

[AndrewJP]

My boss had me switch out engravers on a job and I forgot to calibrate the new engraver which was in a tool holder that was much longer. BAMMMMM!! It scared the hell outta me.

Another time I jogged a 3/4 inch endmill into the side of a Kurt vise. That was surprisingly loud.