Re: 5/8 Ball leadscrew thrust bearing assemblies and nut flanges

Hi all,

Right hand, 5/8-.200 ballscrews are the de facto standard size...
They will generally be the most cost effective IF their size is not a
limitation. ALL the ballscrew mfrs. have tables for figuring
compression loads, resonant speeds vs. end mount types,distance
spanned, etc. For mill drills and many smaller router type machines,
the 5/8 will be suitable. For bridgeport retrofits, and other "heavy
iron" ,you will want a larger diameter. I think a similar
price "break" is available in the 1 inch size, but not as significant
as the 5/8, relatively speaking.

The left hand Y axis ballscrew is an interesting question, and we
spent rather too much time discussing it a short while back on the
sherline list.

The thing is, for the handwheels to work as expected by a practiced
machinist, the screw needs to be left handed. However, used with a
standard graduated wheel, the numbers will be INCREASING while the
axis is moving in a NEGATIVE direction, according to CNC standards.
In other words, if you are a cnc machinist, walking up to a standard
milling machine (sherline to bridgeport, and beyond),the x handwheel
will work as expected, as it uses a RH screw. Clockwise rotation will
give increasing numbers on the graduated wheel, and the TOOL will be
moving in a positive cartesian direction. Now turn the Y axis
handwheel clockwise. The table will move AWAY from you, so the TOOL
TIP will be moving towards you (in a negative cartesian direction).
Meanwhile the graduations will be INCREASING!

So the posters (Cadman) dilemma is an interesting one. Personally, I
use the CNC to move any machine where it is so equipped, and
therefore, save some money(or time, for special ordering) by using RH
screws in both positions. We had (on this list) a pretty long and
strong discussion awhile back about the usefullness of manual control
(NOT "CNC" manual, by way of jog and mdi, but true "hands on" manual)
on a cnc machine. Opinions were strongly worded, and well supported...

So it does boil down to choice. And the choice would apppear to be
whether you are going to still turn the wheels by hand, after you
have CNC controlling them. Also, whether your brain is "conditioned"
to clockwise means table AWAY FROM ME on the Y axis of a mill. This
is important for obvious reasons, especially when reflexes are
guiding the wheels. So I guess there's a third consideration. Will
OTHERS, who have machinist expectations, be using the machine (or
design) as well as yourself...

Hope this helps.

Ballendo

> Also I have not decieded if I want to go with a left hand
> thread ballscrew for the Y-Axis.
> -CADMAN-