From: John Stevenson <john@machines.fsnet.co.uk>

On Sun, 9 Apr 2000 08:49:55 -0700 (PDT), you wrote:

>Hi John,
>
>Thanks for both emails you sent me. More very good
>stuff.
>

>Of these three types what do you think the minimum
>quality I would need?
>
>Is zero backlash an absolutely essential feature? (I
>could probably live with 0.002" backlash if the price
>was greatly reduced.)

On a mill drill I think 0.002" would be sufficient.
zero backlash ones tend to be a lot more expensive.
>
>How much backlash is there in your ball nuts?

Mine are zero but they are a lot larger than what you are considering
and
were made for a production machine.
>
>What are some good brand names for which to look?

Can't comment on this other than say Thompson as a lot of our stuff is
European and probably not available in the US or CN
>
>The ball bearing zeroing idea is a good one. I would
>like to know how others do this. May I post your
>method on the cnc news group to start off the tread? I
>will give you credit or anonymity if you like.

Feel free it has been posted before.
>
>How often do you zero the software. Once per work
>piece or after each cut?

Once at the start of each job. With Ahha it remembers where you were
when
you switch off even if you are not on 0,0
Say for some reason you need to park up at one end of the bed to remove
some part and the display reads X8.500, Y 4.00 and you switch off when
you
start up again the display will read the same. Hit the 'G' key for home
and
it will go to 0,0
>
>Do you experience much stepper motor skip?

No but we never run at maximum rapid feed rates.
Most lost steps are caused by sticking slides, acceleration and
deceleration. Plenty of lube [ way oil - very sticky ] and reduced feed
rates will stop this.
>
>I will also check archives for the people you listed
>who have recently converted to CNC.

Links:-
http://www.seanet.com/~dmauch/
http://plsntcov.8m.com/grizzley.html
>
>Thanks again,
>Peter

--

Regards,
John Stevenson
Special Purpose Machines
Nottingham, England