RE: [CAD_CAM_EDM_DRO] Re: fitting ballscrew ends

Marcus,

For sure the price would have to be low. $50 or less.
Tough.

As far as concentricity understand the internal threads
would snug up on the flank of the groove...it is self
centering even with some diameter variation.

Having to have many types for different screws is a killer though.

I have though of a dedicated rig to rapidly do ends as well.
I fear that my price would still be more than a hobbyist could afford.

I think this is a common problem...Hobbyist buys a set of surplus
or used ballscrews on ebay or something then realizes that he has
6 ends to machine. He probably does not have a spindle bore big enough
and may not be able to deal with issues like the fact that the
lands are usually not good datums for work holding either in
concentricity or yaw...even a 4 jaw is no guarantee. And it's
bearing work... .005 mm tolerances might not be a problem for us,
but could be for the hobbyist. Screw up on the last end and you
have junk.


Wish there was a way to help these folks.

Might not be a product...just a method. I agree that a press fit
plug is actually MORE work than just machining the screw. It still leaves
out those folks that do not have a big spindle bore unless the screw is
short.

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