--- In
Homebrew_PCBs@yahoogroups.com, "gandolfreefer" <synchronousmosfet@...> wrote:
>
> A part that I designed in eMachineShop, keeping tolerances as loose as I reasonably could, came in at about $250...which is actually not at all bad for a cam in aluminum with several turnings offset from each other, even though the part was smaller than a golf ball overall....
>
> ...but here in Metro Manilla I traveled a few miles to a little hole in the wall machine shop and got the same cam made for....$1 USD. Yup, one buck.
Yes, I lived in the PI for many years (though it was many years ago) -- a vast difference in the cost of labor!
> And they normally work to tolerances of +/- 0.0005 or even +/- 0.0001 and were frankly puzzled at the huge tolerances I initially gave them; +/- 0.005 made them think that perhaps it didn't matter WHAT the dimension was....
Interesting. Getting down to .0001" dimensions starts to get to the point where thermal expansion makes a difference. I can cut a part to .0001" easily enough ... in terms of measuring it with my equipment as I am making it ... but it may not be within .0001" after it cools down! :)
>
> PS: one thing that puzzles me about eMachineShop that you or someone may be able to shed light on...in their menu's, they keep trying to force grid spacings on me like 0.098", etc....when I prefer to work with 0.1", 0.050", 0.025", etc. Why the odd numbers? Is it some sort of machining convention worked out over the years to take into account normal tolerances (i.e. +/- .001", etc.), or are these dimensions most easily convertible back and forth between inches and metric????
>
Yep, sounds like they are working off a metric grid.