I have always been interested in the conversion projects. Very interesting.
The problem IMO is most conversions seem to be based around the smaller
mills like that. Is it just because they are such an inexpensive mill?
I do like your motor mounts and how you kept the manual operation. Do you
have an AC side switch so you can turn power off, move your machine, and
then turn power back on without frying your controller with back current?
I did a servo conversion on a 150-Lb mini-mill, mostly as a demo to drag
to shows. You can hit E-stop and move the machine manually, and
then clear the E-stop and be back to CNC operation, without ever losing
the coordinate reference.
It is an ugly hack, as I use it for a test bed of various ideas, motors,
drives, etc. it even has rigid tapping capability.
Retaining full manual capability was a priority. Having to turn on
computer (or wake from standby), log in and run the CNC software just
to drill a hole or two makes no sense IMO. However, I'll have to get
used to the small handwheel for the Z-axis.
I can either turn off the power supply or use a switch that connects/
disconnects power to the drives. Normally use the latter.
Interesting and well documented -- within the limitations which
the web site put on your own added text. I mean who cares about the
camera (a nice one) or the EXIF data when you are documenting a project
like this -- but you live with what the web site will allow. :-)
A question and a suggestion to follow -- both related to turning
the ends of the ball screws:
1) Was it truly necessary to anneal the ends of the screws? I
believe that they are only case hardened, so after a first
heavy cut to get under the case, you should be fine. (Perhaps
with the insert tooling you were using, you could not take that
heavy a cut. I've used that style of insert tooling, and have
long since abandoned them for the more industrial style with a
carbide anvil under the inserts among other things.
2) Looking at the photo showing the teeth of the chuck jaw lining
up with and resting on the crests of the ball screw thread, I
suspect that the other two chuck jaws would be touching at
non-optimum places, so what I would probably do (if I did not
have collets large enough for the task), I would have taken some
aluminum, mounted it in the chuck and marked the point in the
middle of the #1 jaw, then bored it to barely clear the ball
screw, then removed it from the chuck and slit it at a point
midway between two chuck jaws (probably 180 degrees opposite the
marking for the #1 jaw), then put it back in the chuck (using
the mark to put it in the same position), so it would act as a
reasonable collet and be less likely to damage the crests or
flanks of the ball threads.
Good job, anyway.
The ballscrew manufacturer (Roton) recommends annealing for easier
machining. Some posts recommend grinding off the hardened layer with a
grinder (heaven forbid) and those with better carbide tooling
recommend the same as you did. Interestingly, one fellow posted that a
machine shop he approached declined to take on the job for lack of the
Agreed, those little triangle carbide inserts suck even for normal
steel. Hardened steel would probably kill them in an instant. They're
fine for alu, brass and soft metals IMO. Furthermore, my parting
blades are all HSS so annealing it was. No biggie, I had the
Benzomatic already (plumbing repairs).
Several posts on this too. Some recommend using collets and others
recommend filling the grooves with aluminum or copper wire then treat
the ballscrew as a normal shaft. I simply positioned the ballscrew
carefully and had no runout or slipping issues even when using the
Thanks! And thanks for the advice. I really need to upgrade my lathe
O.K. If they recommend it, that should be fine.
I suspect that I might have tried punching a hole in the roaster
pans to pass the rod through, just to minimize radiation heating of the
rest. I presume that the wrapping was soaked in a coolant of some sort
to keep conducted heat down to a minimum.
That is interesting. I certainly would have found a way to do
it myself. :-)
And the interesting thing is that while the holders are cheap
enough in sets, the inserts (alone -- not in the sets) cost more than
those for serious industrial tooling in my experience -- both based on
prices from MSC. For most turning, I use the Aloris BXA 16N
(negative-rake) double ended holder, and inserts with grooves such that
while the holder is negative rake, the net effect is that of positive
rake -- but I still get the ability to turn the inserts over for three
more points, if I don't do something to chip them badly. :-)
In part, I suspect that this is because the shanks don't have
the carbide anvils, so they can bend a little and no longer support the
inserts solidly enough to prevent breaking.
Yes -- collets if you have them large enough and can handle
through spindle diameters large enough for the workpiece. The aluminum
or copper wire might work with chuck jaws which did not have those
precisely spaced grooves. Aside from the makeshift collet which I
described above (quoted), an alternative would be shims of aluminum
between each jaw and the workpiece, likely with an 'L' bend in the end
to let you stop them against the end of the jaws.
I got a lot of my inserts and insert tooling from eBay auctions
back in the days when they had more of usable size (and did not insist
that their vendors use PayPal). But I bought the Aloris BXA 16N *new*
and have not regretted it. Perhaps an AXA-16N for your lathe, depending
on the size.