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darryl
02-19-2003, 03:05 AM
Ok, so I'm human. I'm using this topic to help ease the frustration of a job well done- what? done perfectly wrong! I carefully milled some slots evenly spaced, equal depth, and with a smaller slot centered within each, and, WRONG SPACING! I'm laughing now, but I'd like to laugh even harder. So if any other of you humans would grace us with one of your blooper, hey, we could leave the post hole stories behind! By the way, I wanted to rename this topic 'tales from the scrap bin' but it seems I can't.

[This message has been edited by darryl (edited 02-19-2003).]

Forrest Addy
02-19-2003, 05:53 AM
Dang. That's tough.

Nope. Not me. Never screwed up a single job. Except maybe the 22 1/4 tooth gear but we didn't use it so that doesn't count as an official screw-up.

Herb Helbig
02-19-2003, 07:19 AM
I'd like to see a picture or drawing of that gear!
And its mate!
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[This message has been edited by Herb Helbig (edited 02-19-2003).]

JCHannum
02-19-2003, 07:49 AM
You must refer to those items in your scrap box as experiments, not mistakes. That way people who see them will believe you to be the genius you are and not some total screw up.
For instance, that perfect mirror image of the part you just spent three evenings making was to prove the set up methods.

SGW
02-19-2003, 08:03 AM
I seem to have repressed the memory of most of mine, but I've certainly had my share of "learning experiences."

F'instance, I'm in the middle of building Edgar T. Westbury's "Kiwi" engine. I made 9 rocker arms before I got two good ones. In my defense, I will point out it's a fairly intricate part: http://users.rcn.com/sas.ma.ultranet/kiwirocker.jpg , but it still shouldn't have taken me 9 tries. And the errors were mostly really dumb stuff.



[This message has been edited by SGW (edited 02-19-2003).]

John Stevenson
02-19-2003, 09:53 AM
Hey Forrest,
Will your 22 1/4 tooth gear fit my 42 and a 1/2 splined Alfa Romeo half shaft?

It's easy to be one hole out on a dividing head and the error is acculmative. Pays to do a dry run first.
In my case the guy went ballistic, I learnt a *lot* of new words that day. What made it worse he took the new shaft to a local top notch high priced company and they did exactly the same <g>.

Thankfully those days are gone with the help of Tony Jeffree's Division Master.
Unashamed plug for http://www.divisionmaster.com

Ironically enough this afternoons job is to mill the melted and welded on copper windings from the bottom of 67 slots on a large DC fork truck motor. As some of these larger motors can cost in excess of $4,000 it's well worth the time and effort to repair them.
What would have been a 2 to 3 hour job has now been reduced to about an hour.

John S.

jr45acp
02-19-2003, 12:35 PM
I was taking the machinist's program at the local community college. Was doing first project (evaluative) on the lathe. We called it a test bar, CRS specs called for knurling, multiple diameters, etc. tolerances +/-0.005. I was holding 0.003 and feeling pretty cocky. Was turning last diameter (0.5) Cutting dry, miked and got 0.040 over, took remaining incrementally, hit it with a bit of emery. took it out of the lathe had a smoke and took it to the instructor proudly proclaiming my ability to hold close. He miked 0.5, and it was 20 under. He looked at me and only said, "Go look up coefficient of thermal expansion"! Haven't had a cocky day since http://bbs.homeshopmachinist.net//redface.gif

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John B

gizmo2
02-19-2003, 09:33 PM
Darryl, my luck runs the other way. I make a part, and then figure out what ELSE needs modified to make use of it. In fact, just the other day I had my first perfect day in the shop. Every cut, slot, hole, EVERYTHING I did was within a thou or less. Didn't want the day to end, but was afraid if I pressed on, Fatigue would invite Mr. Murphy in for a party on my tab. My worst? 1973. While transferring a high speed oscilloscope to the clean room cart, I dropped it. Off to Texas Instruments it went: 2 months and $3000 later it was back. Dropped it again while unpackaging it... Depressing to recall the moment, even 30 yrs later!

C. Tate
02-19-2003, 10:09 PM
I don't have a scrap box. I have a box of good parts that have some of the chips removed already.

Techtchr
02-19-2003, 10:14 PM
Do many many many minor screwups add up to a major screup like the scope? Sorry to rub it in gizmo. I make a bad part almost every time I turn my lathe on.

The only major screwup I can come up with is a job I miss quoted. I had a cusomer bring in a very rare instrument that I didn't want to repair, so I quoted him what I thought was a very excessive price. After preping and replating the instrument 3 times I finally got the repair back to him. I think I made 10 cents an hour when I got done.

Matt

darryl
02-19-2003, 10:16 PM
Ooh, the 'scope! I can relate. Many moons ago I bought my first 'scope. A whopping 15 meg, dual trace. What a beauty (then). I got it home, and when I could get back to it (domestic stuff in the way) I plugged it in, then clicked the power switch. Uh oh, what happened ? Lights were out, fridge stopped, in fact as I looked around, there were no lights anywhere, the neighbors, everyone's power was out. My scope did that? Huh? As it turned out, at the moment I turned it on, someone had hit a pole with their car, and knocked the transformer off, it was dangling just feet above the hood. The poor guy inside just stared at it, afraid to move, do anything. Nothing I could do, either. What, get out the voltmeter? The sidecutters?

Thrud
02-19-2003, 10:21 PM
I was building a dividing head with an exact copy of my lathe spindle so I could use my chucks and other goodies with it.

Took a hunk of tool steel and spent a fair amount of time on it, even cut the MT#3 socket. Left the threading for last. Double checked everything (I thought) and set the compound gearing for 8 tpi. Quickly checked it (note "quickly") and cut the thread. Beauty! Measured just right with wires. Bastard did not fit! Threaded it 7.5... http://bbs.homeshopmachinist.net//eek.gif

x39
02-19-2003, 10:31 PM
Oh boy. Well for some reason the first of many to come to mind is the following. I was working second shift in a shop that did machine, welding, and sheet metal work. One night when I came in, there was a job waiting for me and one of my coworkers to do. Basically, it consisted of about two dozen two foot square sheet metal lids with a lip bent all the way around and a notched corner. We had been given a poor copy of the print, and were having a hard time decyphering which way the lips of the lid were bent relative to the notch. We made one part, and we started to doubt ourselves, and after a bit of discussion decided that it was backwards. We then ran the rest of the parts the other way. They looked like a million bucks, and we left them in the inspection room for the morning shift. Yep, you guessed it, we had them right the first time. The owner of the shop was called in to inspection. He had a look at them and said even though they were wrong, they looked so nice he didn't have the heart to say anything to us! And he didn't! We did them right the following night.

JCHannum
02-19-2003, 10:32 PM
Thrud, hope you didn't wast a lot of time machining a register on that spindle.
The last shop I ran had a sign over the office door "Mistakes made while you wait". I didn't take it when I left.

SJorgensen
02-20-2003, 01:32 AM
I guess it is only right that I chime in as well. Luckily I don't have any long term reminders about it, but about a year ago I had a little bathroom plumbing project to do helping my brother out. Mostly easy stuff. heat up the fittings and replace a bathtub manifold. One pipe had to be cut and it wasn't possible to hacksaw it. It was just a little 1/2" copper pipe and I just happened to have handy my 4 1/2" angle grinder. Safety goggles weren't handy. I figured I could close my eyes and turn my head and go right through that copper with one quick cut. About three quarters through, the pipe bound and fragmented the blade. A piece impacted my eye sure as hell. I looked in the mirror, and with my good eye I could see a 3/8" bloody wound in the white of my eye. Long story short, I had to have a doctor check to see if it had punctured my eye. So a doctor probed the hell out of it with some kind of stick and I didn't like that very much. Luckily eyes are very fibrous and tough and heal well (sometimes.) I'm more sold on those nerdy safety goggles than I ever was. It's those quick "one-time" chances that will F#%& you up. Other than that, I still have all my parts. My eye did healed up well.
Spence

Uncle Dunc
02-20-2003, 01:41 AM
I did one right out of the collection of wry old machinst's saying. I bored the hole three times, and it was still too big.

Del
02-20-2003, 10:25 AM
My first honey do after I retired was to shorten a door that was dragging on the carpet. I pulled the door and took it to the shop where I cut off one eight of an inch. Put it back on and still drags. Three more trips to the shop and then my dear wife asks " when I can see over it, will it then fit?" Yep, wrong end. I'll never forget, she won't let me.

motorworks
02-20-2003, 05:08 PM
Hi
One of my main customers had a second shop do some work for them.The customer faxed a drawing to the machine shop to have the part made ASAP!
The drawing was in metric (mm),the guy supplied the part in inches!!
I now get most of the work
e

BasementDweller
02-20-2003, 05:42 PM
This is not really a machinist screw up, but probably my most expensive. I was working for a local silicon chip manufacturer a few years ago. I got transferred to a new department involving the application of high powered laser beams to blow onboard fuses. The job was pretty straight forward, but on my very first night there I messed up. It was basically a machine operator job that required the removal of a set number of wafers for inspection under a microscope. While replacing the wafer into the carrier box, I completely destroyed it. In my self defense, it was about 3:30 a.m. when this took place. After discussing this with my supervisor, it turns out that the wafer was only worth about $75,000.00. I can still hear the "tink" of that wafer snapping.
Eric.

lynnl
02-20-2003, 06:33 PM
Hmmm - bet you were relieved to learn that at least it wasn't something real expensive. http://bbs.homeshopmachinist.net//biggrin.gif

Kevin45
02-20-2003, 07:00 PM
Everytime someone tells me not to screw it up look out. The first big one was a $15,000 custom made cutter from Switzerland. I was a setup man so I set this Japanese mill up. All the other mills would stop when you hit the switch. Well on this one the head would still drop. I was setting a job up cutting three trunnions at a time on a fixture. Beings it was incentive work I figured I would help out the operator by running a few pieces for him. I run the first set of three and decided to clean the packing grease off of the next set. Not too bad but the machine was a little faster than me. So I turned around after the next set, hit the switch to shut it off and proceed to clean some more parts. While doing this I heard a big crunch. You guessed it. I drove that brand new cutter right down into the parts and fixture busting every tooth off of it. 3 weeks later we received a new cutter. I got to set the job up again but with someone looking over my shoulder. The next item on the agenda was where I work now. I had to remove a broken screw out of a $25,000 Boeing landing light. Brand new product ready to ship. Supervisor told me "whatever you do don't break it". Scared the hell out of me when he said that. I used extra precautions when I removed the screw. I retapped it, set it on my bench and went to get the engineer that brought it in. When I turned around I had calipers in my back pocket, caught the wiring harness, turned the wrong way to see what was holding me back and pulled that sucker right off the table to the concrete floor. Man that was a long day and I don't think I ever lived that one down. Have been extra careful for years now after that.

Kevin

JoelK
02-20-2003, 11:11 PM
a few months ago, I was making a backing plate for a 3 inch chuck. Spindle has a 2 1/4 - 8 thread and I was using 3" material. I was trying to keep it as short as possible, so I was threading into a blind hole with a 1/4" from the maximum thread depth to the back of the hole and no end groove. It was a bit nerve racking, even with a clutch break lever and low rpm. I've only been playing at this about a year and it was about the 5th threading project I'd done.

Chipped the bit once, reground it, sync it back up and finished the thread. I was quite proud of myself. Then tried the spindle copy I got with the lathe, won't fit! Goes about 3/4 of a turn and stops. Try a few more passes at final diameter for cleanup, still won't fit. Even try taking 1 thou more off. No go. It's late and I'm frustrated, call it a night.

Halfway through work the next day it hits me. I go home and check, sure enough, I've got the gears set at 10 TPI! Sketch was right on wall behind lathe with big letters "8TPI".

[This message has been edited by JoelK (edited 02-20-2003).]

Thrud
02-20-2003, 11:43 PM
Metric Madness:
I remember a customer ordering two 60"x60"x60" two door cabinet to go on a concrete pad over electrical equipment. Very expensive. Made them up and shipped them out. The guy phones me and screams "What the hell are you doing - the cabinets are the wrong size!" (they had sent a drawing that we quoted on. He says "Juesus this thing should only be about 2 feet square!" I told him that he had better fax me the original drawing, which he did. Wow. I called him back and asked him, "So, have you ever converted metric BEFORE?" "Why no," the replied "but what's the big deal, you just divided by 10 anyways!?"

"Well, sort of...if you convert from the 600mm to 60cm you would divide by 10..."

"Oh, no..."

We ate the cabinets (good customer - its called tossing a donut, they rarely forget it when you save their butts like this) and made him the right ones 60cm on a side at a much lower price.

OUCH:
The local Haas Factory Outlet rep was telling me that one of their customer had a 2" carbide drill in a VMC and the machinist forgot that he had the rapid jog dial set to the z axis until the moment he spun it into the table destroying the drill and spindle as well as the workpiece. http://bbs.homeshopmachinist.net//eek.gif

x39
02-21-2003, 08:41 AM
Here's another one. This happened at the shop my buddy used to work at. They purchased a brand new CNC machining center. The owner of the shop was told by the seller that they STRONGLY recommended that the machine be moved to it's new home by an outfit specializing in moving that type of equipment. In an effort to save a couple of thousand bucks, the owner didn't heed that advice. Well, the guy he hired dropped the machine in the parking lot. My freind said it shook the whole building when it fell. They loaded the machine right back on the truck, and shipped it back to the factory, where they repaired it at the shop's expense. He wasn't so stingy on the rigging next time.

lynnl
02-21-2003, 01:42 PM
This thread is downright depressing...

Chris Fazio
02-21-2003, 02:35 PM
The only people that don't make mistakes are people that don't do anything!!

Chris

Spin Doctor
02-21-2003, 06:11 PM
Theres always the story about the carpenter working on one of the telescope construction project on Kilaewa. The fabricating shop is halfway down the mountain so that the crew doesn't have to worry about people having problems with altitude sickness and running machinery. Well it seems that he kept ordering the smae items too short 'cause he couldn't read his tape because of the altitude. It eally was acase of cut it twice and it was still too short.
Of course just about everybody's missed by .025" or read the depth mike the wrong way.

lynnl
02-21-2003, 08:21 PM
Truer words were never spoken Chris. ...whether machinists, engineers, NASA project management teams, or even governmental officials. Unfortunately some mistakes cost a lot more than others, and affect a lot more people!! As an ex-meteorologist, I'm well acquainted with mistakes and errors. (Not a question of 'if' but rather 'by how much'.) A very humbling 20 years of my life. I guess that's why I like machining... so much more precision. (Not that the mistakes have diminished, they're just of smaller magnitude! ...and I can throw 'em in the scrap box and make more mistakes on 'em later. http://bbs.homeshopmachinist.net//biggrin.gif)

Kevin45
02-22-2003, 01:19 PM
The bad thing about reading depth mics at .025 off is that it is always on the wrong side of the bottom http://www.geocities.com/bat3193/smiley1/spitnono.gif

Kevin

ckalley
02-23-2003, 11:12 AM
I have a magic saw that adds wood for those odd times when I cut it off twice and its still too short!

I'm working on a magic end mill that adds metal, but it's still in development......

I know I have several "learning experiences" sitting around in the shop. I just added another one the other day - 2+2=4, well, at least it should!
Craig