Re: [CAD_CAM_EDM_DRO] Z axis on the knee, how practical????

Jon,
How did you convert the quill on the Bridgeport with ball screw & ball nut?
Thank you,
Al Alfano

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, May 14, 2002 10:22 PM
Subject: Re: [CAD_CAM_EDM_DRO] Z axis on the knee, how practical????


> doug98105 wrote:
>
> > Group,
> >
> > I've been following the discussion of Z-knee conversions. I
> > understand why this is done...because it's easier than fitting a ball
> > screw to the quill.
> >
> > My question involves what it's like to machine parts on a B'port or
> > larger machine with the Z on the knee. Personally, I can't imagine
> > it would be a desirable situation. First off, sometimes I lean on
> > the table as a part is being cut, that wouldn't be possible with the
> > table moving up and down. How about part visibility, isn't it hard
> > to closely watch the cutting action if the part is moving up and down?
> >
> > So, tell me what it's like. Are you guys who are doing this type of
> > conversion experienced with more conventional Z axis (quill) machines
> > or don't you have any basis for comparison? Maybe the Z-knees move
> > so slowly there isn't a problem?
>
> First, let me say I did a quill conversion, and worked hard to keep all of
the
> 5" quill travel of the Bridgeport J head. One of the reasons for this was
> because my knee ways are worn in one area, and the table moves
> in the Y direction at least .001" when you go from up to down on the
> knee. So, I always lower the knee past where I want to go and then
> raise it a bit, to set the knee against the column ways, and keep the load
> off the dovetail part. I will eventually rescrape this machine, but in
the
> meantime, I need to use it.
>
> I do a lot of hole drilling, and some of it is with small bits, so the
feedrates
> get up there where lugging the entire table, saddle and knee around don't
> make a lot of sense.
>
> But, the 5" travel limit is occasionally a pain, and you have to move the
knee
> up for milling and down for drilling with a big chuck and long drill bits.
>
> Jon
>
>
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