Re: [CAD_CAM_EDM_DRO] Re: bridgeport ballscrew question

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