Re: [CAD_CAM_EDM_DRO] Ball Screws for Bridgeport Copy

Hugh Currin wrote:

> CNC Crew:
>
> I'm almost convinced my mill is close enough to a Bridgeport to
> accept a Bridgeport retro-fit kit. It may take some fitting but I
> strongly suspect it will be easier than starting with bare ball
> screws and nuts.
>
> So, I've found four rolled thread ball screw retrofit kits. Those
> being:
>
> Thomson Saginaw .0005 in/ft $3821.30
> Nook/PowerTrac .001 in/ft $1665.00
> MicroKinetics .003 in/ft $ 975.00
> McMaster Carr .003 in/ft $ 743.00
>
> They seem to get more expensive as accuracy increases, ;-).
> I was shocked that McMaster Carr has the lowest cost.
>
> Does anyone know of other suppliers I should contact?
>
> Also, I suspect the lead error is quite consistent along any given
> screw. If this is the case it wouldn't be too hard to scale
> drawings and/or resulting g-code to minimize this.

Why scale DRAWINGS, when you can just set the scale in the CNC control
to give the correct dimensions at all times. not only can you do this,
but EMC
now has machine error compensation, so you can correct for variaions in
pitch
over the length of the screw!

> Particularly
> if, as suggested in recent posts, calculations can be done right
> in the g-code. A few hours measuring should give a very good
> idea what these errors are for a particular installation and see
> if they are consistent. Does this seem possible? Has anyone
> done this?

It is actually quite simple and fast to make these measurements, but you
need a
set of gauge blocks and a dial indicator.

Jon