Geeze, some experts that don't know diddly! I never said I was cutting to that, I said I used those numbers to do the math. As for mattering one of my last projects in the sheet metal shop, I cut material for a storage tank 3000' around and the pipes going around the outside of it. For the math geeks, how high will a pipe be in the air if it goes around the world at the equator and you add one extra twenty feet long joint of pipe? Surely an extra twenty feet at the equator wouldn't matter much would it?
Since there is talk of tolerances, that is one of the first things I straightened out when I was hired at the local nuke to check all drawings from the drafting department except my own. One of the first drawings I saw was a bracket for a pipe hanger, dimensioned to four decimal places! It is debatable what tolerances are when none are listed and a friend was an expert witness in a case arguing just that. However, rule of thumb is one of the last digit so somebody could have somewhat reasonably cut those brackets to one/ten-thousandth of an inch and charged a ton for them at cost plus! A half inch tolerance was plenty tight for those brackets.
Working for the R&D company on the project before going to the nuke we built several versions of a roughly one cubic inch freon compressor. There dimensions were to a tenth as we commonly called ten-thousandths and the tolerances were one fourth that! Fun times but when I spent some time cutting in the neighboring short run production machine shop there were no tolerances on the drawings. Without thinking I asked him if a few tenths were good. He said that would be a bit sloppy and I realized my error. A few thousandths, even a hundredth was OK. Tenths of an inch would be getting sloppy. It was kinda fun hacking out parts after having to reject components because somebody polished one or made an extra spring pass.
To give some idea how tough it is dealing to tenths, I sent a request for bids to forty machine shops. Only two said they could do the job when I just told them verbally that components outside tolerances would be rejected. When I sent them drawings with the same statement on them the last two quickly rejected my request. I was in Louisiana and ended up doing business with a shop on the east coast and one on the west coast.
In my many positions over the years I have ran sheet metal fab shops, metal fab shops, and machine shops. As already obvious, I have been the liaison with and over machine and specialty shops. I have also cut to dimensions that couldn't be measured, they had to be gaged at a certain temperature. Micro-machining before NC was fun but it was a good way to get gray hair or bald in a hurry!
Design work in general was a blast. I got paid for staring out the window. Four days a week nobody could tell if I was working my ass off or thinking about the fishing trip that weekend. Friday after lunch there was no doubt. If there wasn't an emergency to deal with I was planning the stops on my weekend fishing trips. I got my bosses so well trained they would apologize if they brought me something to deal with on a Friday afternoon!
Hu
