On 2012-03-07, Bob La Londe wrote:
"DoN. Nichols" wrote in message
...
On 2012-03-06, Jon Elson wrote:
[ ... ]
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.
[ ... ]
I am in the process of fitting this screw as a lead on the Z axis of a mini
mill. (Smaller than my Taig).
Ouch! Even smaller than a Taig, that leadscrew sounds too
small for the task.
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.
And expect that small a ball screw to flex under similar loads.
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.
Note that Bridgeport had an interesting approach for the ball
screw for the Z-axis (spindle quill, not the knee jackscrew, which was
not motorized). This was in the old BOSS-3, and probably the same up
through the BOSS-8 (which had servo motors instead of the BOSS-3's
stepper motors.
The quill bearing cartridge was built within a cylinder whose
outside was the ball screw, and the corresponding ball nut ran around it
in bearings and was turned by a timing belt. This meant that the force
applied by the ball nut was truly on axis.
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.
It *should* be hard, given that the surface forms the ball race
in the ball nut.
I think that you will find that all the drills which you used
need at least resharpening, if not replacement.
Good Luck,
DoN.
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