Re: X-Y Table, Rotary Table for CNC INFO

Les, Marcus, Dave and others,

Thanks for the comments. This thread has taken on something of a life
of its own, and headed in directions that I didn't quite expect. Very
interesting discussion!

I have a lot of respect for old iron and certainly it's availability and
price represents a good deal for the home or small shop. Believe me, I'm
not a professional machinist or CNC pro. However, I think converting
old iron to CNC use does pose some questions which have to be answered.
One is that used machines have some wear which could affect overall
accuracy and automation can be expected to produce even more wear on
metal that was not designed for CNC. A good machinist can take into
account the individual personality of the old iron and work around its
limitations, but a computer program is not likely to do this. One
special problem in designing a CNC machine is friction and a dovetail
may not be as good as a ground stainless steel rod and a linear ball
bearing. Also, larger servos and steppers will be needed to deal with
the weight and friction. I'm sure all of these factors can be overcome.

All along the way, choices of this type are made as to what is best,
what is affordable, what is possible and what will be the results. I am
sure these questions come up all of the time on this list.

For a large scale operation, cost is a factor but probably not the most
important consideration. The cost of machinery is trivial next to the
capabilities purchased and in the context of a large operation the costs
will be recovered or something is really, really wrong that has nothing
to do with floor production. However, for the home or small shop it's
another ball game. The question is whether we can substitute sweat and
care in design and fabrication and get useful results. The problem is
confounded by the fact that very, very often we want to work on projects
which require a great deal of precision and we want to do it in a
reasonably affordable way--not dirt cheap, but as affordable as
possible.

A bolt-on X-Y table may be just one way to get there. This is certainly
not an original idea. However, it does allow for a great variety of
choices to be made which can contribute to the results we are frequently
looking for. My own need is to make small precision gears on a very
small scale, and I may end up with what may be the first (?) CNC slotter
(vertical shaper) or maybe just use an X-Y table and diamond or CBN
mandrels. For the latter, right now, I'm evaluating the need for an
environmental cabinet.

More later.

Larry Braden
Catonsville, MD