On Wednesday 30 October 2013 13:42:55 Bertho Stultiens did opine:
> On 10/30/2013 04:29 PM, Gene Heskett wrote:
> > As someone from the other side of the pond, I am far more comfortable
> > in inches than in mm or mils for everyday work, but I think I need to
> > understand what a mil is in the definitions you use?
>
> A 'mil' is one thousands of an inch or exactly 0.0254mm.
Good, no confusion then.
>
> My own interest is from my work with PCB design, which uses mils all the
> time. But all mechanics are done in mm. The disparity always annoyed me.
Something I find myself doing fairly often recently, and which has driven
some mods to my mill to enhance the z accuracy.
It amazes me to see all these guys on youtube, using a drill chuck,
dropping the etching bit for contact, hand tightening it, raising the chuck
and taking it up tight with the key, driving their tool 15 to 20 thou into
the fr4 under the copper and calling it a good cut, then they turn it over,
don't even bother to air hose the pallet and then complain because the
'etch' isn't even on one corner. They walk among us, and even breed!
I don't drive the bit even a thou into the glass if I can help it. Harder
on the bit when its cutting glass. I use a g38.2 to find the copper & go
about 1.5 mil below that.
> > Please, can you define the mm to mil conversion, and how that relates
> > to inches for an old man like me who is used to speaking in
> > thousandths for everyday precision measurements?
>
> mil --> mm == value * 0.0254
> mm --> mil == value / 0.0254
> 1 inch = 1000 mil
Good.
>
> > I am in electronics, so to me metric always made sense, but I've been
> > stuck in "Rome, doing as the Romans did for 79 years. This old dog
> > needs to learn metric in the physical world, not just in wavelengths.
>
> Well, electronics still has a lot of imperial measures in use for PCB
> design.
Yup, trying to keep it sorted in eagle can keep you on your toes.
Cheers, Gene
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