Re: part holding

Tom, How about some pictures?

Keith Clark

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Tom Hubin <thubin@e...>
wrote:

> Hello Rick,
>
> > The hardest part about cnc is not the electronics, the servos,

the

> > ballscrews. The hardest part is holding down the friggen part!
> <snip>
> > How do you guys hold down a part when
> > you want to machine 5 surfaces on it?
>
> I make fixtures for the parts. I use dowel pins (usually 1/8 inch
> diameter) to securely and accurately locate the parts on the

fixture. I

> can remove parts, inspect, reorient, and replace within a fraction

of

> 0.001 inch.
>
> I often make a "standard" that can be installed on the fixture. The
> standard allows me to use an edge finder to locate sides for X and

Y

> referencing. Then parts can be dropped into the fixture without any
> change of X or Y reference.
>
> Sometimes I reference Z to a standard top surface too. That is

handy if

> I want to flycut several parts to a particular thickness.
>
> Minimum of 2 dowel pins to locate and orient a part. I often use 4

or 5,

> especally if that many dowel pins will be used to mate pieces in a
> complex but precise opto-mechanical assembly.
>
> The fixture itself may be secured directly to the XY table or it

may

> just be replacement pieces for jaws in my vise.
>
> Tom Hubin
> thubin@e...