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Robin S.
 
Posts: n/a
Default Interview for a machine shop position


"Dave Lyon" wrote in message
news:yFlbg.952791$x96.450759@attbi_s72...

I'm a garage hacker and have no idea or desire to achive that level of
tolerance. Just curious, can some machines do that just from knobs and
such or does it require more finesse?


Most people that claim to be holding those tolerances are full of crap.
I'm
not pointing fingers at anybody, cause obviously it is needed for some
tools, and can be done. But, it cannot be done in a general shop
environment
day in and day out.


And therein lies the rub. Day in a day out. You can finesse some pretty
tight numbers out of most machines, you just don't want to have to do it all
the time.

Most surface grinders can reliably hit .0002 over a smallish area. Manual
jig borers have dials graduated in .0001 or .0002 (it's been a while since
I've seen one). Cylindrical grinders can hit those numbers reliably. There's
basically no chance that a Bridgeport/knockoff can reliably hit .001" in a
production setting, and it has to be setup correctly to hit even .001".

As far as why you'd want to, high-speed dies require some pretty tight
numbers. Automotive engines require very tight numbers over hundreds of
thousands of parts. I'd assume there are others ;-)

I think a lot of people don't appreciate how far off things become when you
have the right tools to measure them. The way holes are curved, plates are
not flat, cylinders are not round or straight, etc.

Regards,

Robin