Re: re:re: ground plates

Guys,

The trick to get flat plates or other items is to go to a grinder
that knows what he's doing. Yes, the mag chucks may pull warped
plates down flat and they'll still be warped when the chuck is
released, but in that case you're dealing with an idiot for a grinder.

IMO, these are not issues that should overly concern the customer.
These issues are the responsibility of the grinder. You tell him
what you expect and it's his problem to make sure it happens or he
shouldn't take on the job.

My favorite grinder guy has all kinds of tricks to deal with warped
plates and he always tells me upfront when he anticipates problems
that may cost more to deal with. He's even used hot melt glue to
hold pieces down for an intial smoothing of one side.


Doug

--- In CAD_CAM_EDM_DRO@y..., "Elliot Burke" <elliot@h...> wrote:
>
>
> Paul Amaranth <paul@a...> writes:
> Subject: Re: Re: ground plates
>
> On Tue, Jul 09, 2002 at 08:59:15PM +0000, bjammin@i... wrote:
> > At 04:24 AM 7/10/02 -0000, you wrote:
> > >Dave,
> > >
> > >To get plate that'll end up flat after grinding is a two step
process.
> > >First it needs to be stress relieved by a heat treater, then
ground.
> >
> > Actually, this won't do it. Mag chuck will flatten it, then when
it's
> > released it will spring back some. To get flat, you need to
suppport it on
> > chuck so it isn't stressed in any way.
> >
> > Regards, Hoyt
> >
>
> >I had a vertical bandsaw table Blanchard ground. I wanted to get
it
> >flat because some idiot had tipped it over and the table had a
distinct
> >bend in it. The mag chuck pulled it flat for grinding and, when I
got
> >it back, it still had the bend in it. But at least it was pretty.
>
> > Paul
>
> I also have had things Blanchard ground. A cheap chinese 6" joiner
bed,
> about 40" long, was visibly out of flat.
> The Blanchard guy flipped it upside down, supported the working
surface from
> the magnet with a few carefully chosen shims so that it was resting
at three
> points and level, then leveled the four mounting feet.
> He then flipped it over and carefully removed metal from the table
surface.
> Worked great, and its still quite flat.
>
> I should put the autocollimator on it to make sure, though.
>
> This technique could be used in other applications if the metal
being ground
> was moderately stiff, maybe not the case for 1/2" thick 15" long
steel.
>
> The trick would be to evenly support it.
>
> Maybe a bed consisting of a couple of layers of bb's?
>
> Some sort of pin device like they sell in novelty stores might
work, a block
> of metal with lots of holes, pins through the holes. The block
sits on the
> chuck, the spring loaded pins support the work, when the magnet
goes on the
> pins are frozen in the block.
>
> Other ideas?
>
> Elliot Burke