EDM "machining"

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Amazing accuracy...guy also explains tolerances and thermal expansion somewhat...but the precision is astounding.
 
We regularly machine some aircraft parts down to .7499" - .7500" tolerances (a very common part)

Some parts require honing the hole very slowly to bring it up to the exact dimension ( .2500" + or - 0.0000" )

I can see the need in the future (especially when making these new "extremely high pressure" fuel injectors, where machining to the .00001" will be needed
 
The green diesel engine plant I retired from kept the whole factory at a constant temp, and humidity year round for micron tolerance. Nice temperature to work in too.
 
Capable of 0.000050" tolerances with relatively straightforward process controls.
That's 50 millionths.

We did lights out machining of 3.500" thick die sections and held +/- 0.0002" and this was 15 years ago.
Set it up, let it cut all weekend.
Monday morning empty the used wire bin and drop the parts off for CMM inspection.

Scandalously easy to make money with the right customers...
 
It's been many, many years since I worked for the first EDM company that was able to do 5 axis wire EDM. 0.0005" was the standard tolerance for their basic machines, and that was a barn door to the "premium" machines. All it took was brass .010" wire; clean water; and time. One of my first training for programming involved a hexagon "cylinder" with a full 360* twist in a 2" thick piece of steel that was accurate to 3 decimal places... nearly 18 years ago. If you were willing to set insanely long cut times... 50 millionths was available. No idea what today's best EDMs are capable of.

EDM is an amazing technology, albeit not the fastest.

That's not even considering the accuracy of the die-sinking machines which used graphite "electrodes" that were used to make things like cell phone case pieces, etc.... the metal moulds were only limited by the accuracy of the CNC machine that had machined the chunk of graphite that was making the metal mould....
 
at Boeing we would bore sign key holes . 200." apart. in an aluminum plate. 1.5 " to 2.00" thick. + 0r - .001. for a press fit. sign key .
 
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