> > CNC drilling seemed to have been high on wish lists in the
> group until
> > the resident machinist declared that any backlash greater
> than .001"
> > (or some similar nonsense from his
> > textbook) just wasn't going to cut it.
> > Surprisingly, he seems to still drill by hand.
>
> I reckon I woudl be happy with one thou
> backlash. And if I was not happy with it I reckon I would
> just always approch a hole from the same direction.
>
> CNC is a must I feel fot PTH. If you don't have CNC you have
> to do and extra photo development at the start to act as
> guide to drill by.
1/1000" is 0.0254mm. More than enough for thru hole PCBs. The errors don't
accumulate, so even 0.1mm accuracy is enough (especially for hand assembly).
And you drill the holes oversize anyway.
A quick and dirty way to eliminate backlash on a lightweight machine is to
attach a tape measure (or two) to it. A tape measure contains a negator
spring (like a clock spring) and provides a constant force. Hook one to the
X & another to the Y axis, same principle as using a counter weight.
You can adjust the negator for more/less force, and replace the tape with a
cable so it looks more 'professional'. You'd be surprised at the amount of
force you can get. Obviously the cheaper the tape measure, the sooner it
will fail. Good negator springs are expensive, tape measures are dirt
cheap.
Tony