Re: Knee for z-axis control?

as for myself, I am planning on using the knee for Z... with gas
sturts... a $100.00 solution

why?

well, for a TOTALLY different reason than any given

I use my right-angle head about 20% of the time so I want to be able
to use my vertical mill in limited horizonal mode, arbor and all, and
a quill Z would be useless to me.

in my case, knee is the only option unless i want to build either TWO
machines (and I don't have a horizontal) or i build two Z.sure, i
COULD job the quill down, and only use xy... then again, i could just
use my powerfeed in the same fashion... and THEN run into
the "inaccuracy" of the knee

then again, I am planning on the first version being preloaded acme
(ACME) screws... if the accuracy isn't there, then I'll worry with
ballscrews...

backlash? in my BP knee... there isn't any today

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "doug98105" <DougR@a...>
wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "pondindustrial"
> <pondindustrial@y...> wrote:
> > Hi all,
> >
> > I will be retrofitting my Bridgeport mill soon and know that some
> > have used the knee for z-axis control. Does anyone here have any
> > experience with this method? If so, what should I take into
> > consideration if I decide to go this route? The mill has a 9" X
> 48"
> > bed.
> >
> > Is a counterweight to offset some of the lifting load preferable?
> > Did you use the original acme screw/nut, or retro with a

ballscrew?

> > What would be a reasonably sufficient drive in terms of motor
> torque
> > and gear reduction?
> > What are the pros & cons of using the knee opposed to the quill?
> >
> >
> > Thanks, Eric
>
> To my knowledge there are no commercial CNC knee mills (B'port

clone

> types) with the Z on the knee. Ever wonder why? You would think
> that at least a few builders of CNC machines might use this method
> if it had some merit.
>
> In spite of the apparent success of some conversions mentioned

here,

> to me it seems like total nonsense to have that much mass jumping

up

> and down at traverse rates we normally expect of a CNC mill.
>
> Just my $.02,
>
> Doug