Re: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends

Hi Les:
I have to agree with Dave (turbolatordude) that the cost of making an
extension is likely to be higher than the cost of farming the work out to a
shop with a cylindrical grinder.
The other big difficulty, of course, is getting the concentricity you need
to keep the ballscrew from wobbling...your customers are likely to expect
this whether it's realistically achievable with aftermarket parts or not.
As you know, when you're working to a tolerance band and expected to fit
pre-existing parts that you have no access to, you've got a much more
difficult challenge than if you can fit the parts together in-house.
If there was enough demand, and people were willing to ship me their
ballscrews (and pay the two way shipping) I'd grab myself a big old
cylindrical grinder on E Bay for a couple of thousand bucks, and have at
'er.
With a 16" diameter wheel on a big Cincinnnati, I could probably spin down a
journal end in a couple of minutes.
The whole job would be in setting up and indicating in, unless the screw
already had centered ends.
Cheers

Marcus

----- Original Message -----
From: "Leslie Watts" <leswatts@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, June 10, 2005 5:31 AM
Subject: RE: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends


> Marcus,
>
> I also find machining ballscrew ends not really a big deal. I do
> use an offhand grinder to remove most of the hardened land material
> though...saves a bit of time and helps prevent interrupted cutting
> with the carbide tool.
>
> I think part of the issue is the tools available. Perhaps many hobbyists
> do not have lathes with large enough bores to accommodate the screw,
> or they do not have enough rigidity. We don't have that problem...but
> we are not hobbyists.
>
> Here's a thought:
>
> What if there was a pre-machined ballscrew end that just screwed on to
> the unmachined ballscrew end? Internal threads would engage the screw
> ball race area rather than the sometimes non concentric lands.
>
> It would have to be pinned (taper pin) but a pre-drilled hole could
> facilitate
> making the hole. Perhaps some rough offhand ground "flats" in that area on
> the
> screw would allow the use of ordinary drilling and reaming methods.
>
> I could make such a product...but I have not considered how much it would
> cost.
> The logistics of having to have many different models for different screws
> is an issue. The threads would not have to be exactly the same profile
> though...
> just something that engaged a particular pitch and minor diameter in an
> angular
> contact fashion.
>
> What do you think?
>
> Les
>
> Leslie M.Watts
> L M Watts Furniture
> Tiger Georgia
> (706) 212-0242
>
> Main page:
> http://www.lmwatts.com
> Engineering:
> http://www.lmwatts.com/shop.html
> Cnc surplus for sale:
> http://www.lmwatts.com/forsale.html
> Carved signs:
> http://www.lmwatts.com/signwp.html
>
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com]On Behalf Of Marcus and Eva
> Sent: Friday, June 10, 2005 1:02 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends
>
>
> Hi John:
> Aren't you concerned about splitting the end of the ballscrew if you
try
> to press fit a stub in to the end?
> It's a case hardened screw, and the small root diameter is not going to
give
> you a lot of meat for a decent sized stub.
> Even in a best case, you'll bulge the end of the screw and make the last
bit
> unuseable to drive the ballnut on.
> That's probably not the end of the earth if you plan your design so you
> can't run the ballnut over it inadvertently but you do have to be aware of
> the problem and design accordingly.
> All this seems an awful lot of farting about, to avoid what really is
still
> a pretty simple task.
>
>
>
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