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.
I just can't see what's so hard about turning down the ends of the ballscrew
with carbide and lapping or polishing the journals to size if you feel
uncomfortable trying to hit the journal size by turning alone.
Thousands of people, including me, have done it this way without great
agony, and I still maintain that it's easier to do and less risky than
making and accurately fitting an extension to the screw by whatever means.
It's also undeniably stronger, and though your point about motor shafts
being assembled to motor armatures with nothing more than a press fit is a
good one, the contact area and the relative diameters of the motor
components do make a good bit of difference in the strength of the assembly
as compared to what one might expect with a stub extension grafted onto a
ballscrew end.
Cheers

Marcus

----- Original Message -----
From: "John Stevenson" <john@...>
To: "CAD_CAM_EDM_DRO@..." <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, June 08, 2005 4:39 AM
Subject: [CAD_CAM_EDM_DRO] Re: Re: Re: Model Engineers Workshop volume103


> A good press fit with loctite will more than stand the amount of force a
stepper can put out on machines of this class.
> Bear in mind that 99% of electric motor up to 10kw only have the shaft
pressed into the rotor and these never slip.
>
> John S.