Re: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends

Hi Les:
I like this idea much better; it's certainly much easier to do for the
price point you're talking about.
Probably better concentricity too.
The hardest part will be getting the balls to stay where they're supposed to
as you slip the stub shaft over the end of the screw.
A spring or spiral wire slipped over the screw groove will certainly be
easier for the hobbyist to install.
Cross pinning the hardened screw will still be difficult for a guy with
limited equipment to do, unless he softens the end of the screw first.
He's also going to hit the wire with the drill, so the drill is going to
wander a bit.
I bet you'll get enough time consuming phone calls from frustrated hobbyists
to strip any profit out of the job in a real hurry.
That Cincinnati that Fred Smith is talking about, is starting to sound
pretty good.
Fifty bucks an end gives you almost an hour an end to work with...but the
customers will have to send their ballscrews to you.
I think that's a good thing...you have far better control over the outcome,
so you'll have far fewer complaints and queries...both money losers.
It's not a bad sideline if you are already in the build-it-yourself CNC
business, and can afford to have a machine standing mostly idle while you
scare up customers.
I certainly don't have the space for a machine like that in my shop, and I'm
up in Canada, so the cross border hassles and attendant costs would kill
this for most of my potential customers.
Cheers

Marcus

----- Original Message -----
From: "Leslie Watts" <leswatts@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, June 10, 2005 8:57 AM
Subject: RE: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends


SNIP
> I am considering a similar slip on end as before, but with no internal
> threads.
> With a gothic arch screw have some balls loosly affixed in the grooves-
> perhaps held on with a dab of rubber cement on the side. With two measure
> the
> overall diameter including the balls.
>
> Machine the end cap bore to a line to line fit with that diameter. Put
> 6 balls on the screw (two groups of 3 at 120 degrees) and slip it on.
> squirt in filled epoxy and perhaps pin it.
>
> If you screw up the ballscrew is not damaged.
> The cap is a short soft piece that does not require a large spindle bore.
> It can be easily made (including bearing locknut threads) without fancy
> stuff.
>
> The usual spiral wire wrap is also an option...but balls are more precise.
>
> ???
>
> 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 10:49 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: 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
>
>
>
>
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