Re: [CAD_CAM_EDM_DRO] Re: Ballscrew mounting

----- Original Message -----
From: Jeff Swayze <jswayze@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, March 21, 2001 12:43 AM
Subject: [CAD_CAM_EDM_DRO] Re: Ballscrew mounting


> Sounds like a good plan, Joel. I never considered drilling the ballscrew
> and inserting another piece with the features already turned on it. The
> darn screw is so hard it would be very difficult to turn and thread it.
> Great idea! Question: what do you plan to drill the screw end with? I
> tried it tonight on a scrap piece of ballscrew and even using a HSS stub
> bit the hole was still slightly off center. It just didn't want to bite.
The
> point at which the tip of the bit hits the material seems to be the
> critical issue. If it walks at all any other drilling will be off...

Hi Jeff,
Drilling the screw is not my idea, someone on this list mentioned it and it
seems like a good plan. I guess the screw is case hardened and the center
should be softer so it makes a lot of sense. I hadn't thought about keeping
the drill centered but a couple ideas come to mind. You could use a tool in
the toolpost to turn a depression of sorts in the end of the screw first,
that would help center the drill. Or maybe rough out the hole with a drill
and finish it with a boring bar?

Joel



>
> FWIW, I've taken apart the table and reassembled it. The Y axis is
> mounted exactly the same as the X except the end of the lead screw is
> just floating in space. The tricky part is reassembling the nuts - you
have
> to plan ahead :)
>
> Good luck. I'll post pictures of my progress on my website one of these
> days.
>
> http://www.swayze.org/shop
>
> -Jeff
>
> --- In CAD_CAM_EDM_DRO@y..., "Joel Jacobs" <jj@n...> wrote:
> > Hi Jeff,
> > I'm in about the same place with my mill/drill and I'll share my ideas
for
> > the conversion with you. I got 48" of .75 X .200 screw from
> McMaster-Carr.
> > The thrust bearings on both axis will be just two stacked 5/8id deep
> groove
> > ball bearings with shims between the inner races. I will make new end
> > blocks to house the bearings and clamp the outer races. I will
> machine stub
> > shafts with a shoulder and threaded portion to fit the bearings. I will
> > attach the stubs to the screw by drilling about a 1" x .375 or .5" hole
in
> > the end of the screws and a machining the stub for a slip fit and use
> 271
> > loctite to secure. The y axis will only be secured at one end. The x
axis
> > will have these thrust bearings only at one end with the other (motor)
> end
> > exiting through a single ball bearing. With the thrust bearings
> oppisate
> > the motor end I will be able to fiddle with the shims without removing
> the
> > motor.
> > For mounting the nuts - On the x axis I'll make a block about 1"
thick,
> > bore a hole in it and thread it to fit the nuts and thread a nut in each
> end
> > so there will be two nuts. I'll slot the block and put a bolt through
so I
> > can clamp the nuts from turning after I get them adjusted.
> > I haven't figured out the y nut mounting yet because I can't see in
> there
> > very good. I need to take the machine apart and get some ideas. I
> do have
> > a single circuit nut that I was lucky to get with not more than .001
lash
> > and I'll use it on the y. I won't need to double nut that one. I may
get
> > some half thou oversized balls and polish the screw till I get a real
> nice
> > fit.
> >
> > Wish me luck!
> >
> > Joel
>