"DoN. Nichols" wrote in message
...
On 2012-03-06, Jon Elson wrote:
Bob La Londe wrote:



"Bob La Londe" wrote in message
...
Its metric. I bought it off Ebay a while back because the price was
right, but I can't find the descriptive number anywhere now. I would
like to get some more the same size, but longer for an application, but
for the
life of me I can't recall the screw number to look for. Its 6mm
diameter
and the pitch is about 1mm.

http://imageshack.us/photo/my-images...ballscrew.jpg/

After much search I am beginning to think this is a fairly rare size
ball
screw.
Yikes, looks like it is a very fine pitch. Well, the only thing that
matters is the diameter and pitch. Your 6x1 makes me think
6 mm dia and 1 mm pitch.

Which is a finer pitch than that used on the Compact-5/CNC, and
which is otherwise a similar length. I think that the Compact-5 uses
one of 8mm diameter, but I've never actually needed to measure it.

I have actually seen some like
that listed on eBay, so you ought to just search there and
see what comes up. The real problem is they are rarely made very
long as whip and stiffness become problems.

Agreed. Bridgeport, in their BOSS-3 through BOSS-6 machines,
even with a ball screw larger than one inch, and with the speed
limitations of their original stepper motor setup, did a trick to
minimize whip. The Y-axis is normally driven by rotating the screw, but
the X-axis has the screw rigidly mounted to the right end of the table,
and rotated the ball nut (in a pair of opposed bearings) instead. A very
good way around the whip problem, but perhaps not enough for stiffness
on a 6mm ball screw.

Good Luck,
DoN.

I am in the process of fitting this screw as a lead on the Z axis of a mini
mill. (Smaller than my Taig). I was hoping to finding something similar
for the X&Y, but I either can't find them or the price of a single lead
assembly is more than the whole machine. I had retrofit that machine from V
groove to Acme a while back, but the anti-backlash nuts I found for that
size are just to puny. Under light aluminum cutting loads the nuts give
constantly. Can't really use anything bigger in the space available. I
suppose I might be able to use 8mm, but that would be it, and I would have
to drill out the table and cross slide for clearance.

P.S. That nut is freaking hard. I tried to drill it out slightly so 6/32
mounting screws would go through easily, and I had to do it one drill size
at a time, and I still cooked two bits even while pouring oil on them while
cutting. If I find more of these they will get 4/40 screws for mounting.
LOL.