Re: bridgeport ballscrew question

Thanks for the explanation Jon. After i read your message i relies i
did not understand the function of the yoke...I thought it was
something to support the screw and stop it from whipping around. I
see now that all the forces to move the table go through the yoke.
Without the yoke the table could not move as the ballnuts would not
be secured to "ground".


Wally

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
> cnc_4_me wrote:
>
> >WOW, that sounded like a big job...And that explains why the yokes
> >are castings and so funny looking (to complicated to machine all
> >those clearances needed out of a block)....
> >
> >If i were to attempt to make one, i would try it in
aluminum...Much
> >easier to hack clearance in were you need it...Steel must have
been a
> >killer.
> >
> >
> Aluminum is not stiff enough for the purpose. The yoke receives
1000 - 2000
> Lbs of thrust in a CNC machine on fast acceleration, maybe more in
a crash.
> Well, it IS a full-size Bridgeport except for the Y travel. It
wasn't
> that big a
> deal to make the yoke. The mounts for the X and Y axis drives WERE
a
> big deal.
> The X axis mount started out as a 111 Lb chunk of 2" hot rolled
steel.
> By the time
> I was done, it was a 44 Lb. honeycomb, with a bunch of odd angles
in
> it. And, I had
> to do all that manually!
>
> >Arn't there any drawings of this stuff floating around...
> >
> >
> >Wally
> >
> >
> >Thinking about this a little more, i think the only purpose of the
> >yoke is to support the Y screw since it has no bearing mount on
the
> >rear end....The yoke stops the Y shaft from wiggling off center...
> >
> >
> The yoke holds the nuts for the X and Y screws. I don't follow
your
> last sentence
> at all. The Y screw is supported at the handle end by a dual
bearing
> set, and at
> the nut, wherever it is on the screw.
>
> >I think it also provides a false sence of security on the X axis,
> >since when the table is all the way over the yoke isn't at the
middle
> >of the X screw...And the X screw has bearings at both ends
anyway...
> >
> >I guess what i am getting at, is that a aluminum yoke should work
> >fine...At least acording to my arm chair engineering...
> >
> >
> It carries all forces that the screws apply to the table and
saddle.
> The idea is to
> put the X and Y nuts as close together as possible.
>
> Jon