Re: re:re: ground plates

--- 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

A trick I have used in the past instead of shimming the plates when I
ground the first side is to wax up a known flat surface and to apply
bondo (yea the autobody filler stuff) to the peice you are going to
grind on the side you are having down on the chuck first. Press down
on your waxed suface (might want to move it around a little to get
thin) and let it set up. after it sets up knock it free from your
known flat suface (you did wax it good) and you have a surface to put
down on the chuck with built in shims.

mike