What was the dumbest machining mistake you ever made?

[george wilson]

Back in the early 70's I made a dividing plate very carefully from brass.(not the correct one I've posted here before). I did a nice job with careful detailing on it,and several rows of holes. Then,I realized I had put 24 holes in EVERY circle of holes!! Might have made a classy bath tub drain or shower head!!

 

[Tony Wells]

That's a tall order, George. I have so many to choose from. Do we want the most expensive, or simply the most idiotic? I think I can fill the bill either way.

 

[Bill Gruby]

I ain't touchin that one Frank.

George, I could probably write a few pages on the Dumber ones. I gotta think a little on this one.

"Billy G" :lmao:

 

[george wilson]

I am getting lots of confessions,but no examples!!

One of my apprentice musical instrument makers(when I was master instrument maker in Williamsburg) visited a guitar maker in Newport News and brought back a guitar top with the sound hole cut out of the LOWER BOUT instead of the upper bout. That might have been a $100.00 German spruce top!!

Another dumb thing I did was to break off a 1" 8 thd. tap!! I very seldom ever break off a SMALL one,not even #00 80. I was in a hurry,and tired,and thought I could tap a piece of brass in the lathe by jogging the motor. I didn't even jog it much,either. Broke the sucker right off.

Tony,the most idiotic would be funnier!! You can make an expensive part .001" too small and ruin it,but just being absent minded is funnier.

 

[jumps4]

last I remember was grabbing a 1/4" drill for a 1/4" tap in a hurry
it got 5/16 bolts
steve

 

[jumps4]

you said dumbest, sorry
answering the phone while threading on the lathe, I just spun around to get the phone and bang
cost me a set of gears in the headstock, I was lucky the gears protected the slipper clutch
steve

 

[jworman]

Would you be meaning today??

The other day I was making an attachment for the 1 1/2" receiver hitch on my Toyota. I slipped down to the metal store and purchased a piece of 1 1/2" square tube. It didn't take me too long to realize that 1 1/2" was the size of the receiver. 1 1/4 was about right for any attachment.

Luckily, I was able to recover and use the purchased piece.

 

[Tom Griffin]

I can laugh about it now because no one got hurt, but I was once setting up a Hurco CNC mill and was distracted by a phone call. Long story short, I neglected to bolt down the 6" Kurt vise and it was launched off the table like a piece of wood, landing on the floor about ten feet away. Luckily, even though the old Hurco was pretty much bullet proof, the workpiece absorbed all of the abuse and nothing broke, not even the end mill. A 6" Kurt vise with swivel base weighs around a hundred pounds which should give you a pretty good idea of the produced by a 3HP spindle motor. Let's be careful out there.

Tom

 

[OldMachinist]

I'm sure I've made many mistakes over the years but my memory ain't what it used to be. I do remember the most recent. I was getting ready to dress the wheel on my surface grinder and was interupted by somebody. When I went to dress the wheel I hadn't turned on the magnet. The wheel dresser went flying across the room and punched a hole in a door. The diamond was gone and the wheel had a nice chunk missing.

 

[george wilson]

Seems like telephones and distractions are the cause of many accidents.

Years ago there was a letter in Fine Woodworking magazine from a guy who was changing the blades in his Makita Jointer. He had not unplugged it and the knives and gibbs were loose. He answered the phone and came back and turned the jointer on. Everything flew out and broke a hunk out of a separate piece of steel that comprised the edge of the indeed table. Lucky for him there WAS a separate piece of metal there,or he'd have lost the whole infeed table.

His letter was to gripe about the poor service he got from Makita replacing the part. All he got from the readers was a load of how stupid he was!!

I loaned a 12" Parks planer to a friend. He was changing knives when another friend came in and turned the Parks on. The gibbs were thrown out and mangled. They paid money to buy new gibbs!! This was in the 70's,and luckily new gibbs were still available.

The moral is obvious: UNPLUG your machines when working on them!!