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When the machining doesn't go according to plan...

E

Elektrishun

Well-Known Member
...how often do you try to hide your mistakes?

I am not a professional woodworker but I did spend a lot of years building numerous projects of varying degree of difficulty. One of the common sayings I heard/read in the woodworking profession was:

"90% of woodworking is knowing how to fix your mistakes."

Now that I am getting more into the world of making mistakes while making metal shavings I was wondering if there is a similar philosophy when working with metal?

It seems to me that the tighter tolerances often needed to make something with metal wouldn't allow for much room for error unless your churning out paper weights or catapult ammunition.

Would like to hear from members how often they need to fix an error or does 90% of errors in your machining end up in the scrap pile?


I assume a one time hobby project on manual machines vs a professional run of several like pieces using CNC equipment might change how you answer.

Thanks
 
I think the axiom still holds. 90% of my time is fixing mistakes whether it is metal or wood. Just with wood the mistakes are 1/4” and in metal they are 0.010.

I am building some stationary steam engines from casting kits. Of the 10 or so pieces I have done so far I’ve messed up most all of them. Sometimes by 0.002, and sometimes I’ve needed to remake a part from stock I have on hand.

The way I look at it is it’s cheaper than a course at BCIT or SAIT, and I sure am learning stuff. Worse case scenario, it looks nice on the shelf but won’t run. Best case, it runs.
 
I think it depends on what we define as a mistake and on what the work is.

If blowing a target is a mistake, it happens. But not very often.

If measuring or designing wrong is a mistake, it happens more often than I would like. But no where near 90%. Maybe 2 or 3%.

The vast majority of my machining is farm equipment repair. If I blow a target, nobody notices or cares if they do notice. An 8 inch by 1-7/8 inch pin just has to fit.

More often than not, my designs are in my head and hard numbers don't exist. I work to an idea and the idea evolves as I work toward a goal. "That will work" or "close enough" are very real machining terms for me.

A small portion of my work is what I would call precision work related to my hobbies. For this work, I am very meticulous. I can take weeks to do what a pro could do in a day, or a day to do what they could in an hour. As a result, mistakes are very rare. When they do happen, they are usually due to a process that didn't go as planned - eg an annular cutter makes an oversized hole. When that happens, I am not a happy camper.
 
There's an interesting saying I heard many many years ago. "The difference between a professional and an amateur is the professional knows how to cover up his mistakes".

Perhaps "cover up" is an insult and the reality is "recover from". When I do a circuit design and then PC board layout there can be mistakes. For example the first lamps for the barge based ring set had an interesting RF noise that happened to be right in the middle of the float plane radio frequencies.

Given that the barge had been towed and anchored where the float planes normally taxied in Vancouver Harbour you can understand there were some people who weren't happy. I tried to fix it with a variety of filters etc. No luck. Only a circuit change and new layout got rid of the RFI. But we were out of time. The new boards were never put into production.

Should it have happened? It didn't for the airport rings because I knew there would be airplanes flying over. And we had an extra few weeks. The barge rings were under a tighter schedule and the lamps had to run off 48V batteries that saw a charging voltage of almost 60V. The existing lamps wouldn't work.

So they made electrical RF noise and we put in a process to be able to shut them down in case of an emergency.

So I didn't cover up the mistake but it was there. Instead we worked around it.

I believe mistakes happen all over the place. It's only with volume production that on each iteration there are improvements made until the parts come out perfectly.

The heat sinks made by Custom Machining here in Central Saanich were perfect. But the late Rick Salaga had his whole life experience to draw on. How many samples he made before the product came out perfect I don't know. I never saw those. But I don't believe his first prototypes were as perfect as the production devices.
 
I find it easier to be a good machinist when I'm following a drawing - mine or someone else's. The chance for recovery is much less, as it's either to the drawing or not, but so is the chance for error when the brain is no also trying to design. I do some designing on the fly, but usually just on simple stuff and it often ends up being the long way home. I don't find it as enjoyable either compared ti just concentrating on the sequence, work holding, tooling etc when in the shop.
 
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Susquatch said:
More often than not, my designs are in my head and hard numbers don't exist. I work to an idea and the idea evolves as I work toward a goal. "That will work" or "close enough" are very real machining terms for me.
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I usually at least make a sketch (and drawing if it's something more complex/with multiple parts/may become an article), and this does reduce errors. However, ther are (frequent) times when a dimension changes or I rethink something during machining/fitting, and the drawing changes – since the final result matches the drawing I guess that means it's not a mistake/error?

Susquatch said:
A small portion of my work is what I would call precision work related to my hobbies. For this work, I am very meticulous. I can take weeks to do what a pro could do in a day, or a day to do what they could in an hour. As a result, mistakes are very rare. When they do happen, they are usually due to a process that didn't go as planned - eg an annular cutter makes an oversized hole. When that happens, I am not a happy camper.
Click to expand...
Gret point: that is one of the things we learn as we get deeper into the hobby: what requires precision and what doesn't.
 
Susquatch said:
I think it depends on what we define as a mistake and on what the work is.

If blowing a target is a mistake, it happens. But not very often.

If measuring or designing wrong is a mistake, it happens more often than I would like. But no where near 90%. Maybe 2 or 3%.

The vast majority of my machining is farm equipment repair. If I blow a target, nobody notices or cares if they do notice. An 8 inch by 1-7/8 inch pin just has to fit.

More often than not, my designs are in my head and hard numbers don't exist. I work to an idea and the idea evolves as I work toward a goal. "That will work" or "close enough" are very real machining terms for me.

A small portion of my work is what I would call precision work related to my hobbies. For this work, I am very meticulous. I can take weeks to do what a pro could do in a day, or a day to do what they could in an hour. As a result, mistakes are very rare. When they do happen, they are usually due to a process that didn't go as planned - eg an annular cutter makes an oversized hole. When that happens, I am not a happy camper.
Click to expand...

I think that saying is emphasizing that when a woodworking pro makes a rare mistake 90% of the time they can fix it, have it function, and look flawless.

Whereas the amateur now has a choice - start from scratch and or have a mistake/repair that sticks out like a sore thumb.
 
The reason I am asking about fixing errors is because I am currently working on a project that is revealing how far from an acceptable level of accuracy I am able to achieve.

It's a one time project for myself and so far I think it will still function to an acceptable degree but if it were meant to be a Christmas gift I would be starting over.

I like how you worded this:

@Susquatch
A small portion of my work is what I would call precision work related to my hobbies. For this work, I am very meticulous. I can take weeks to do what a pro could do in a day, or a day to do what they could in an hour. As a result, mistakes are very rare. When they do happen, they are usually due to a process that didn't go as planned - eg an annular cutter makes an oversized hole. When that happens, I am not a happy camper.
 
I took a course called Technical Drawings. It was really 'drafting 101' but technical drawings sounded better. I do detailed drawings for most of my projects. They help me visualize my end goal and also it's where I make most of my modifications.

If tested, I'm sure most of my welds would fail, but the results are usually OK for my purposes. Sometimes, my welds look awful because of improper procedures—thank goodness for a grinder! But I am a self-taught welder. Those poor welds that others would call mistakes are OK to me. Grinding them out and then changing parameters or techniques is part of the learning process. So, having to redo a weld is an acceptable mistake because I learned from it.

I had a good friend who was considered an expert in his engineering specialty. He often said, "I don't know how smart I can afford to get". While giving expert testimony, a lawyer asked him "What makes you an expert?" His reply "I've made more mistakes than the other guy".


jcdammeyer said:
Perhaps "cover up" is an insult and the reality is "recover from"
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I believe a code of conduct or professional ethics would/should eliminate a "cover-up".
But sayings like "The difference between a professional and an amateur is the professional knows how to cover up his mistakes" unfortunately exist because not all professionals are professional.

A mistake is not a bad thing.
Good things are: learning from a mistake; recovering from a mistake; avoiding a mistake; or fixing a mistake.
A cover-up is a bad thing.
 
“Cover Up” is a harsh term: many times field/existing conditions or choice of materials or purchased parts require after-the-fact changes or modifications to the end “product.”

A close to home example of this:

IMG_9065_Radiant_Photo.jpeg

30 years ago when I added cove molding to the existing kitchen cabinets after we wallpapered everything was good until I got to this condition: I came up with the best solution possible, and in those 30 years no one but me has ever noticed it.
 
So here is a recent "design feature" for the project I am working on:

Project.jpg


That bolt was supposed to thread directly to metal piece. Unfortunately, do a poor start, poor technique, just f*****g poor...it did not thread properly but at a noticeable angle. Like, if you looked at it from across the street noticeable angle.:(

What to do? It took a bit of time to get that metal to the right dimensions (i do not have a milling machine - just grinding, filing, etc.) so I wasn't going to remake it unless necessary.

I didn't want to drill it out and go up a bolt size.

So I turned a nut on the lathe to make it fit the newly drilled-out opening and used JB Weld. This is where I appreciate @Susquatch comment about how much time it takes when you're not a pro or in my case barely an amateur. I needed the nut to fit just right. That meant taking a measurement and then, when I thought that I was close, test fitting the metal piece to the nut while still in the lathe (backing off the tailstock again and again...). Very time consuming but now the bolt threads in properly.

But if I needed to make 3 more I would probably have started from scratch to make 4 and found a better way to tap the threads vs turning 3 more nuts on the lathe.

Edit: I should mention the repair doesn't interfere with the function whereas the mistake would have impaired the function.
 
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Mcgyver said:
I find it easier to be a good machinist when I'm following a drawing - mine or someone else's. The chance for recovery is much less, as it's either to the drawing or not, but so is the chance for error when the brain also trying to design. I do some designing on the fly, but usually just on simple stuff and it often ends up being the long way home. I don't find it as enjoyable either compared ti just concentrating on the sequence, work holding, tooling etc when in the shop.
Click to expand...
I agree with the statement that is is easier to be a good machinist when following a plan, and know it to be true for myself because I usually don't have a plan. Now I'm not doing any real high end work for NASA (or the Flintstones for that matter) but usually making some tool or gadget for myself, or I am doing a repair of some sort.

Having said that, yes I have obviously made lots of mistakes and I would say about half the time I am able to fix or proceed with the project despite the setback.

I've learned to incorporate a motto we used to use with our kids when they were little "Ooops, that will be a beautiful mistake". They were trying to draw something and it ended up being a squiggle so we would try to help them to see how that squiggle could be turned into something "beautiful".

Well I don't think I've yet managed to make any of my mistakes into something "beautiful", I have created new "features" or "alternate designs " :p
 
When I was coming up through my apprenticeship I was taught that everyone makes mistakes no matter how good or experienced. The difference between an amateur or apprentice and a professional is a professional has the knowledge and experience to know how to fix the problem in the most appropriate way and carry on. People with less knowledge and experience have to take more time to figure out what to do and might spend a lot of time and or money to solve the problem. Fit a part in the wrong spot and don't find out until it has affected other parts do you take it all apart and waste all the time spent getting to this point or can you make an adjustment on another part and keep going? What does the job call for and what is allowed? Things like that. I once welded lugs that connected the ends of conveyor sections, mirrored to how they should have been, onto about twenty sections. some had already been blasted and painted. I was just starting my apprenticeship and thought that it was going to be a huge deal to cut them all off and welded them all back on then reblast and paint each one. Each section was 40 feet long. I owned my mistake and went to my boss for advice. He spent 2 minutes taking to the engineer came back and said make a note on the drawing and make sure I do the rest the same way. As long as they were all the same they would all connect and work. Was over a mile of conveyore when we were all done. Learned a lot of lessons on that including how to slowdown and properly read the print before starting.
 
Mistake ? Meh, never happens.

18 years old, building a house for the first time with my flight instructor. Also his first house. We did everything, nothing subbed out. Electrical inspector shows up, takes one step inside, looks up and mutters "amateurs". Our hearts sink. He explains that if we had wired it "professionally" the wires would be going every which way, not neatly lined up with 90* corners etc.
 
I can not remember what happened to the engine that was involved, I think it toasted. I was doing a part replace on an engine, “the big boss” showed up and demanded that I leave that project and go with him to work on another unit else where. I protested, said I needed another 10 minutes to finish what I was doing, as it was at a point somewhat important to get all bolts in place and then torqued in a very difficult order and torque rating. NO, come right now, this has to be done, no time to wait!! Off I went, did and finished that job, got back at end of day. Burnt out and cold (winter). Came back in next day, and a big rush to get the engine out I had been working on, did not remember what I had not finished, put unit together and got running. Came back 2 days later in bad shape, with the “big boss” ranting about poor work and so on, how I had made a mistake and so on. My supervisor said everyone make mistakes, and it was very hard not to make a mistake around the outfit with nearly no spare parts to maintain equipment, sometime stripping one to keep other going and so on. The “big boss” states that he never makes mistakes!! My supervisor replied “that’s true. But you don’t do anything either”.
So remember, if you don’t do anything you will not make a mistake. The difference between a mistake and a total disaster is being able to figure out how to make it work with the mistake, modified or otherwise, that part is often called “experience”.
 
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