Workshop Mistakes (True Confessions)

No secret I'm not a master craftsman, but I hope it's obvious I want to learn! And I've no problem sharing blunders so that other self-taught beginners can make faster progress than I am.

"What's the clown done now?", I hear you asking!

Well, I'm squaring off a 140x160x35mm block of cast-iron for my Experimental Pendulum project using a WM18 milling machine. Having done most of the job successfully, I took a deep gouge out of the top surface, whilst tidying up the rear wall.

As common in accidents, this blunder resulted from a chain of causes. And, typically of me, the main driver was operator error rather than my Chinese mill, inexpensive cutters, or a slightly difficult material.

• all that's needed for the project is that the top of the block be machined flat. Though not strictly necessary, it was useful to machine the base as well, partly because a clean face makes it easier to clamp the block to the table and reference later cuts. This stage was completed successfully, then I made the first mistake: I decided to machine the block true and square on all sides "for practice". Rule 1: if it ain't bust don't fix it!
• However, yesterday afternoon, I got stuck in and successfully machined the two long sides correctly. Took quite a long time and revealed some problems I chose to tough-out: My mill is a little too low for my height, so I have to stoop slightly to twirl the lower controls. Not a problem normally, but I developed back-ache as the session proceeded; Silly Old Duffer isn't as fit as he used to be! Approaching the evening meal, I was tired, hungry and very thirsty. Rule 2: know when to stop!
• Nonetheless, having made good progress, and with 20 minutes in hand, I decided to carry on and finish the rear-face. Now I'm tired, hungry, thirsty, in pain and working against the clock. And it's very easy to make difficult situations worse. Rule 3: don't be rushed into making decisions or doing work unless it's genuinely urgent.
• Machining the rear face required the block to be upended, with a different clamp arrangement. On making a change, do not assume previous experience automatically applies. Rule 4. Think about it!
• My new clamp arrangement was solid right-left and down, less satisfactory front-back, and relied too much on the weight of the block to stop it lifting. I knew this, and went to get a G-clamp. Unfortunately my G-clamps couldn't easily be reached because I'd temporarily stored wood in front of the box. I allowed my tired muscles and hurting back to override good judgement. I decided, as I was only skimming the top that the block wouldn't lift. Rule 5: Brain knows best, don't ignore it!
• Making the first cut, I noticed starting was difficult and then suddenly got much easier, then harder with a mushy feel. I thought it odd, but carried on regardless. Bad mistake. At first the cutter broke through the hard outer skin, but then the hard edge caught in the helix and lifted the block off the table causing a deep gouge. Though the block weighs 6kg, and was restrained by two angled clamps, an 1100W motor is powerful enough to lift the job into the cutter and hack deep into the cast-iron. Wouldn't have gouged deep had I stopped, but I didn't react to the clues. Rule 6: when a cut suddenly sounds or feels different, make sure it's OK, and not an early warning of real trouble.

So I finished the day tired, hungry, thirsty, hurt, and knowing I'd made an entirely avoidable problem, spoiling a job that had otherwise gone well. Lots of opportunities missed to avoid the blunder. For instance, had I stopped for an early meal and recharged my batteries before finishing, I'd have fitted a G-clamps. The amount of work needed to reach them was insignificant, and I only wimped out because I was tired.

Let my shipwreck be your sea-mark!

That's my sad story. What mistakes have you learned from?

Dave

Edited By SillyOldDuffer on 09/03/2023 10:58:24

Do not go into the workshop when cold, tired and suffering from a headache. Leave it for another day.

That way you are more likely to connect the 24vdc input terminals of a stepper motor driver to the 24vdc output terminals of the power supply, not the 240vac input terminals.

On the plus side I can confirm the existence of ball lightning.

regards,

David

IE, "The nut that holds the handwheel".

Don't assume it is only self-taught beginners who drop clangers. I was told very early on that a good tradesman is not one who never makes a mistake, but is one who knows how to fix his mistakes. (Or at least hide them. Which means he probably won't post them on the internet for all to see!)

Here's one: Very early on in my chequered career I had the job in a car assembly plant toolroom in Zimbabwe to machine up some quite a few dozens of cast iron trolley wheels to run on an overhead track to carry car bodies along the production line from hangers. They were rough castings about 6" diameter, flanged like a train wheel and had to be machined all over and bored with a recess to take a big 4" or so diameter ball bearing. So I machined them all up over a week or so, then gave them to one of the African apprentices to press the bearings in. But somehow I had managed to bore them all a thou or two too tight so when they were done, the bearings would not turn, they had closed up with the pressing in. So we had to press all the bearings back out again, set each and every wheel up true in the four jaw chuck painstakingly, and skim about two thou out of each bearing recess then reassemble.

Never did tell the foreman. He just thought i was painfully slow at getting the job finished. As an old Glaswegian tradesman out of the shipyards once told me "Just act dumb and you will always get by". (In that particular case I did not have to act too hard!)

I've made just about every mistake, usually for the reasons mentioned by Dave.

David's post reminded of a mistake I made when I was very young. I was outside the house and turned around to see a brilliant blue object floating in the air about six feet away from my head. I backed away very slowly and made myself elsewhere!

The mistake was telling my parents and schoolteacher about it, I quickly understood than strange weird and unusual things were not subjects for discussion unless you wanted to get locked up.

I can also vouch for the existence of ball lightning.

daveb

Edited By daveb on 09/03/2023 12:12:54

Here is what I am talking about, hiding your mistakes. The ball on the end of the handle on my lever tailstock was SUPPOSED to be just a perfect sphere with a flat on it where the handle screwed in. But in my faffing about, I set up my jury rigged ball turning tool about 75 thou too far toward the end of the blank, resulting in the bit left sticking out where it joins the handle as seen in the above pic. It looked pretty ugly with a V groove in it from the turning tool and flaring out. So rather than scrap the job and start all over again, I simply turned the most of it down parallel as seen and blended the small remaining V groove in with a file. Until it all looked like that is how it was supposed to have been in the first place.

It was good enough to fool most of the people most of the time and made it onto the front of MEW so can't have looked too bad! Looks quite the part with a lick of paint, which covers many sins. Sometimes you get lucky.

Ive lost count of the number of times Ive called myself a moron and worse

Yes, when I get to thinking, I could write a book...

Too many but I have never damaged myself.

In my experience it is always the operator's fault.

The blame culture does not work in your own workshop. When I get the chance I need to start a lessons learnt log (just like work). It will be a spread sheet with all entries in large upper case Ariel bold. Perhaps I may use it as a screen saver.

JA

I was working in a shop that made geological exploration sondes. I had to machine a flat on a cylindrical diameter that was part of a longish complex component called a caliper body. I'd already set it up on a Bridgeport, in a dividing head with tailstock support to drill, then ream or tap, a number of holes in angular relationship to each other and the flat, which was the last feature to machine. I think the piece already had several hours of machining time done on it.

I used plastic tape to wrap the divvy head chuck end of the part to protect the existing finish.

When the endmill hit the cylindrical diameter to cut the flat, the workpiece rotated in the chuck, gashing teethmarks in the end face of the diameter and bending the slender protruding end diameter. Obviously I should've foreseen it, but my mind was more on the holes when deciding on the setup.

It was only because of the clock-and-mallet skills of the chargehand (an otherwise quite unpleasant man disliked by most of the machinists) that the bent bit could be rectified within a few tenths, the teethmarks machined out without loss of function, and I managed to keep my job.

That was 1976. I can only talk about it now because I've lived it down in my own mind since, and seen others, who should also have known better, make hugely more expensive mistakes.

My guess is that it happens to most engineers. They always say that anyone who never made a mistake never did owt that mattered.

Edited By Mick B1 on 09/03/2023 13:36:51

Ive lost count of the number of times Ive called myself a moron and worse

Me too but recon the worst was getting 4 jaw chuck stuck on lathe and I mean stuck to the point I had to wreck the backplate to free it

H

Many many mistakes both at work and in the home workshop, but one of the most amusing to the rest of the workforce was when I was asked to measure up and order some stickers to go on some electrical switchgear control boxes saying " Danger equipment fed from two separate sources" or some such. Never having ordered anything like this before I measured very carefully and as the boxes were quite small decided that 100mm x 150mm would be most appropriate,ordered 1000, filled out the supplied form and forwarded to the department that printed our signs. A week or so later came the message " theres a truck in the loading bay with stuff for you, where would you like it put, as soon as the forklift is free we'll shift it for you". Puzzled, went to the loading bay to find several very large heavy boxes waiting for me, on opening found 1000 huge signs 1m x1.5 , turns out the form carefully filled out was clearly in cm not mm! Boss took it remarkably well, the boxes were carefully hidden and were still there as a constant reminder when the firm closed down a few years later, every so often a huge sign would appear stuck across my locker or draped across one of the machines, Still get reminded of it forty years on!

Edited By Dave Wootton on 09/03/2023 13:54:16

Edited By Dave Wootton on 09/03/2023 13:55:28

Real skill is making your disasters look like they were a deliberately planned part of the job

Mine are far too many, and too embarrassing to enumerate. One place I worked backed onto the canal. Rumour has it that barges would go aground on bits machined in error and chucked out the window to avoid the foreman's wrath.

My biggest workshop mistake was ever entering one in the first place, got talked in to it and by the time I realised it was not what I wanted it was too late, stuck turning handles for a lifetime.

Hi, yes I've made many silly mistakes, both at home and at work. The last one I remember making in my final day job, was cutting up material which only enough was ordered each time on one customers items which were made on a four to six week periods, depending how quick they would wear the previous ones out. Cutting up the material, which was 25mm dia. EN8, meant putting aside four uncut lengths four each of four fabs, as their lengths were cut at the end of each fab. I then had to cut 40 short lengths and eight long lengths, but! eight lengths had to have three short lengths and one long length cut, however, I must have got a bit carried away cutting the short lengths first, but I realised just in time that I wouldn't have enough material to get the four longer lengths. The next but! was, what was left over was not long enough to complete the number of short lengths, and butt welding any bits together was unacceptable, however, I was lucky enough to find some odd off cuts in the stock shed that would complete the job, but. yes there was a third one, two or three of them were about 20mm shy, however, this is where fortune shined on me, as all the short lengths had to have a short section bent to a right angle at one end, which can be seen in the photo below. This sort section is where all these short lengths were welded to each of the four uncut lengths and this bent section could tolerate the odd shortcomings here, and so the mistake could be to some degree hidden by not putting them all on the same fab. Needless to say I had to deliver them to the customer the day after the were finished and no comments or complaints were made from them.

Regards Nick.

Edited By Nicholas Farr on 09/03/2023 15:55:40

As an apprentice marine engineer many years ago in the mid 1970's, I once cut a 6 inch dia hole (approx 150 mm!) in the wrong place in the hull in the very bottom of a new ship.....fortunately it was in dry dock at the time....

I still have that piece of hull plate on my table as an over large industrial coaster for my mug of tea, to continually remind me to measure twice cut once !

Regards to all

Derek

Best I can remember at sea was the entire engine room staff trying to get a cylinder head off the main engine. Swarming round frantically, the main hoist pulling at it, chainblocks, hammers, iron bars sweating, aggression, desperation

I only watched for a couple of minutes then made myself scarce

It took a while until someone noticed it had been welded on

TOO many to list! ranging from Apprentice to quite recent

Howard

Not me but a work collegue, tasked with milling a flat on the telescope of a brand new Theodolite. ( Maybe £3000 worth) It was duly strapped down on the mill table and the shell end mill starting to cut when it caught and threw the the Theodolite out onto the floor. Frantic check of theodolite and then reset on the mill and double clamped. Then succesfully machined Much touch up needed but ended up OK. He kept his job!

My latest (of countless):

Carefully measuring and working out that I could just get a Minnie cable winding drum and driving centre out of a piece of cast iron bar, very carefully setting up, extremely carefully machining the part, and one feature left to do on the driving centre which was to be a press fit in the gear which I'd made some time ago. Went to fetch the gear to get the required diameter and found that I had already made and fitted the driving centre.