Re: [CAD_CAM_EDM_DRO] Re: Flat as a (very precise) pancake...

Hi Tom:
It is the length to thickness ratio that determines the magnitude of the
problem.
A 1/4" thick block 2" long is easy to grind flat within 0.0002"
A 12" bar of the same thickness can be an impossible nightmare to get flat
within 0.005"
Similarly, a 2" thick bar 60" long will be a real challenge to get flat and
to keep flat.
This is why you want a deep section for any support pad for a linear way.
It will have sufficient stiffness to pull the linear rail straight.(linear
rails ain't straight right out of the box either!!)

Cheers

Marcus

----- Original Message -----
From: Tom Murray <thomasm923@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, March 27, 2001 9:11 AM
Subject: [CAD_CAM_EDM_DRO] Re: Flat as a (very precise) pancake...


> --- In CAD_CAM_EDM_DRO@y..., "Marcus & Eva" <implmex@a...> wrote:
> > Hi Tom:
> > The problem is that skinny stuff won't stay flat even when it's
> > precision ground.
> > Getting it flat and getting it to stay flat is really hard to do.
> > Precision ground stock is usually parallel within 0.0005" but
> that's about
> > all.
> > Cheers
> >
> > Marcus
>
> What is considered the "skinny stuff"? I was thinking about using
> 3/8" to 5/8" stock. Would the above problem still apply?
>
> Tom Murray
>
>
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