"We can inspect the parts when they send them back"
"Fuck it, It's [that one consumer goods company which sends purchase orders to an ISO 13485 (medical device manufacturing) facility for some reason]"
All jokes aside, tight tolerances DO NOT indicate good engineering. Anybody can add a bunch of extra zeros to a fucking blueprint. A well engineered part / assembly will have things toleranced as loosely as permissible, with the exception of a handful of critical dimensions, and a good design will ensure that even those critical dimensions don't need to keep the machinist running back and forth between the grinder and the laser micrometer.
Excessively tight tolerances will cause a lot of perfectly functional parts to be scrapped, require additional machining operations, more expensive tooling, more frequent tool changes, increased rework, increased machine operator skill, increased inspection frequency, etc. etc. etc. When some fuckstick like Elon Musk comes around and says they're tightening the tolerances to make the fucking door panels line up correctly, they're telling you they have no idea what they're doing.
Holding tight tolerances is a matter of workmanship. Engineers are supposed to be the ones figuring out where that effort makes the most impact and where it makes no difference whatsoever.
God the over right tolerances have been the worst experience with parts I have ever inspected.
Piece of plastic with drilled holes into it with about a 12" OD true positioned to 0.0002" to the OD the center ID and the bottom of the part. We got everything consistent enough to 0.001" and called it good enough lol. Place was a literal clown show with so much wasted talent cause of a management shit show
What the fuck. Plastic will lose that .0002" tolerance if somebody farts in the same room (especially .0002 over 12 inches!). How do you even measure the location of a hole that size? If you're trying to nail the position down to .0002 what the fuck is the cylindricity supposed to be? Atomically perfect?
I’m over here thinking about temperature changes. It will be precise within 0.0002” at the ambient temperature on whatever Wednesday at whatever time
Going by a thermal expansion calculator, if the part is steel, then a temp increase by only 20F will cause the length to increase by 0.0048”. Idk what the coefficient of expansion is for plastic, but it also has one and it’s probably going to result in variations larger than 0.0002”
Lower tolerances is what allowed the Soviets to whiz past the entire Axis combined in terms of tank production. The only difference was a Soviet KV-1 could put a shell through the front and out the back of a Panzer IV a kilometer away while the Panzer's shells would bounce off at 200 meters.
"If it fits, it ships"
"We can inspect the parts when they send them back"
"Fuck it, It's [that one consumer goods company which sends purchase orders to an ISO 13485 (medical device manufacturing) facility for some reason]"
All jokes aside, tight tolerances DO NOT indicate good engineering. Anybody can add a bunch of extra zeros to a fucking blueprint. A well engineered part / assembly will have things toleranced as loosely as permissible, with the exception of a handful of critical dimensions, and a good design will ensure that even those critical dimensions don't need to keep the machinist running back and forth between the grinder and the laser micrometer.
Excessively tight tolerances will cause a lot of perfectly functional parts to be scrapped, require additional machining operations, more expensive tooling, more frequent tool changes, increased rework, increased machine operator skill, increased inspection frequency, etc. etc. etc. When some fuckstick like Elon Musk comes around and says they're tightening the tolerances to make the fucking door panels line up correctly, they're telling you they have no idea what they're doing.
Holding tight tolerances is a matter of workmanship. Engineers are supposed to be the ones figuring out where that effort makes the most impact and where it makes no difference whatsoever.
God the over right tolerances have been the worst experience with parts I have ever inspected.
Piece of plastic with drilled holes into it with about a 12" OD true positioned to 0.0002" to the OD the center ID and the bottom of the part. We got everything consistent enough to 0.001" and called it good enough lol. Place was a literal clown show with so much wasted talent cause of a management shit show
What the fuck. Plastic will lose that .0002" tolerance if somebody farts in the same room (especially .0002 over 12 inches!). How do you even measure the location of a hole that size? If you're trying to nail the position down to .0002 what the fuck is the cylindricity supposed to be? Atomically perfect?
I’m over here thinking about temperature changes. It will be precise within 0.0002” at the ambient temperature on whatever Wednesday at whatever time
Going by a thermal expansion calculator, if the part is steel, then a temp increase by only 20F will cause the length to increase by 0.0048”. Idk what the coefficient of expansion is for plastic, but it also has one and it’s probably going to result in variations larger than 0.0002”
Lower tolerances is what allowed the Soviets to whiz past the entire Axis combined in terms of tank production. The only difference was a Soviet KV-1 could put a shell through the front and out the back of a Panzer IV a kilometer away while the Panzer's shells would bounce off at 200 meters.