Home› Main Category› Clubhouse
Linefinder
Posts: 7,856 Senior Member
My toughest machining job yet.........
Linefinder
Posts: 7,856 Senior Member
I'm probably the oldest toolmaker apprentice in the world. I don't have enough working life left to become really good at it, as I'm reminded almost every working day. But this project was bad.....oh my gosh......it was bad.
Engineering needed a pin (or dowel, if you prefer). 2.79" long with a diameter of .046" out of hardened stainless steel. For the half inch off each end, the tolerance was "if we can measure a difference, it's not close enough". The remainder of the pin had a tolerance of +.0000"/-.0003".
Knowing this was going to be a tough act to pull off, I stared off by prepping, heat treating and drawing 5 blanks. Then off to the grinding room where equipped with a surface-grinder, spin indexer, and counterbalance fixture, I ruined all of them in less than 45 minutes.
Back to the stockroom, and prepping and heat treating ten blanks. This took me into day two. (For a simple pin, mind you......simply a pin).
Long story short.....nearing the end of day two, I had two blanks left when I finally got one that I think meets spec. I say think, because Metrology took off early on Wednesday, and there was no one there to "officially" measure my part. What a way to start the T'giving holidays.
To add insult to injury, engineering estimated two hours to produce this pin. Best I can figure, I had almost 16 hours in it. But, OTOH, our most skilled toolmaker told me it would have taken him only two or three tries (he spent five years on a surface grinder at another company) to do this part, but also said it would have taken him just about as much time.
If this pin doesn't pass Metrology on Monday, I'm gonna open a vein.
Mike
Originally, my intent was to use a "close sized" mold ejector pin, but as per normal......everything we had on hand was either too small (no good at all), or slightly too big (not much better).
Engineering needed a pin (or dowel, if you prefer). 2.79" long with a diameter of .046" out of hardened stainless steel. For the half inch off each end, the tolerance was "if we can measure a difference, it's not close enough". The remainder of the pin had a tolerance of +.0000"/-.0003".
Knowing this was going to be a tough act to pull off, I stared off by prepping, heat treating and drawing 5 blanks. Then off to the grinding room where equipped with a surface-grinder, spin indexer, and counterbalance fixture, I ruined all of them in less than 45 minutes.
Back to the stockroom, and prepping and heat treating ten blanks. This took me into day two. (For a simple pin, mind you......simply a pin).
Long story short.....nearing the end of day two, I had two blanks left when I finally got one that I think meets spec. I say think, because Metrology took off early on Wednesday, and there was no one there to "officially" measure my part. What a way to start the T'giving holidays.
To add insult to injury, engineering estimated two hours to produce this pin. Best I can figure, I had almost 16 hours in it. But, OTOH, our most skilled toolmaker told me it would have taken him only two or three tries (he spent five years on a surface grinder at another company) to do this part, but also said it would have taken him just about as much time.
If this pin doesn't pass Metrology on Monday, I'm gonna open a vein.
Mike
Originally, my intent was to use a "close sized" mold ejector pin, but as per normal......everything we had on hand was either too small (no good at all), or slightly too big (not much better).
"Walking away seems to be a lost art form."
N454casull
N454casull
Replies
One of my firearms mentors was a tool & die maker.
It'd be my guess that even incredibly smart people can't have a lifetime of experience without the lifetime part.
Jerry
Maybe. I'm getting used to working within a thou, but man, this thing sure was long compared to diameter. The chatter was what ate my lunch. I've no idea how to hold something so long and thin that insures less than.0003" chatter. If I did indeed successfully pull off this part, it's pure dumb luck. It'd probably take me just as long (or longer) to do it again.
N454casull
D
Alcohol, Tobacco, Firearms and Explosives.... now who's bringing the hot wings? :jester:
My worst job was not machining but lapping, we had to lap the oil seal end of gears with diamond dust and check them with a color optical comparator, if the color was not all the same shade of red, it was out of tolerance, the oil seal itself was a "carbon seal"
JAY
Jerry
No, they didn't. Which makes it even sillier. The diff between room temp and after holding this pin in your hand for ten seconds is almost a couple thou. They don't ever think of things like that, so I always assume ambient temp.
Mike
N454casull
I said they were engineers. I never said they were good ones.
N454casull
Good engineers, from any field, are really smart, capable guys/gals. The problem is that mediocre engineers are more prevalent, and still have the same arrogance that nearly all of them seem to have. I've always said that a full year of their training concentrates on teaching them to belittle problem solvers who can make stuff work without 5-6 years of college training. As a land surveyor, my worst frustrations came from dealing with civil engineers, surpassing even lawyers and realtors. It is a pleasure to work with an engineer who loves simple solutions to complex problems, but there aren't enough of them to go around.
Your problems most likely arise from a failure in engineering, for hanging too much emphasis on an unrealistic level of precision. If it's a prototype for some great new invention, that's one thing. But, if it is the final product and this is actually the mass production final solution, the engineering is bad.
The female body had to be designed by a civil engineer- - - - - - -who else would put the toxic waste dump right next to the playground?
:uhm:
Jerry
I'd rather be lucky than good. But I'll never again do this without a fight that'll make the pencil-pushers pee themselves.
Mike
N454casull
Jerry
Lesson learned.
Mike
N454casull
While the .0003 tolerance is tough, the problem really was simply that the aspect ratio of thickness to length was ridiculous. As to the numerical tolerance itself, the real toolmakers just consider it another day at the office.
Mike
N454casull
N454casull
Gun control laws make about as much sense as taking ex-lax to cure a cough.
Mike
N454casull
Mike
N454casull
I can barely understand the description !
You have an engineering background it seems ��
N454casull
Shamelessly stolen!:worthy:
George Carlin
Child's play. I can do that with my eyes closed, almost. I'm ashamed to work for a company that allows such slop.
But sometimes, it's a nice break. Today was a nice break.
Mike
N454casull
Sounds like fun in any case, the success part really.
One of my favorite construction sayings: "I've cut this stud twice, and it's STILL too short!"
"Close enough for Government work!"
"Good enough for the girls I date"
George Carlin
Until you find extra equipment !
One of the favorites I have learned; "Looks good from my house!"