Re: New guy needs advice!

At 06:18 PM 11/9/2000 +0000, you wrote:

> I'm very excited about purchasing my first CNC milling machine, and
>want to make sure I get the right one 4 my needs....

I'd say if you want to machine a 6" turbine out of stainless you're way out
of the mini-mill league. Some argue if you take small enough cuts, and as
long as the piece will fit, you can do anything on a mini-mill but there
are limits. Motor power, tooling and rigidity are big problems. If you
have the floor space, I'd look at the Shoptask 3-in-1 mill/lathe (
http://www.shoptask.com ). It comes CNC ready for $1895, has dual 1hp
motors and weighs nearly 900 pounds. They have a few CNC packages starting
at around $1000 in kit form or you can do your own. For not much more than
the price of a MaxNC 15, you can have a "real" machine. Of course you'll
need an engine hoist to move it around.

You may want to consider the Shoptask "quadra lift" option to adjust the
mill head height. Without it, you either have to use spindle extensions to
bring your tooling down to the table or block your work up to reach the
spindle (with either losing rigidity). This is a common problem with most
3-in-1 machines--most only have about 3" of Z (quill) travel.

The Shoptask, particularly without ball screws, won't match the precision
of a good mini-mill but it will tackle much bigger projects (the Shoptask
has enough lathe swing to handle even automotive brake rotors and
flywheels). Another option would be one of the Smithy machines (
http://www.smithy.com ) such as their 1220 XL Limited CNC. I believe
Smithy, however, only sells their CNC option as a full package for about
$3500 (plus about $2000 for the machine) making it more expensive than the
Shoptask.

Besides the above options, you're left with doing your own CNC conversion
of a small machine. Grizzly ( http://www.grizzleyindustrial.com ) has an
interesting "big" mini mill for $495 (the G8689) and they have a fairly
nice "real" mill for $895 (the G1005). There are also a variety of under
$1000 3-in-1 machines but most have very limited milling capacity due to
the spindle being only a few inches from the lathe faceplate so they
wouldn't mill your 6" turbine. None of these machines are CNC ready and it
would take quite a bit of work (especially on the Z axis) to fit
CNC. They're also all made in China and are not of the precision or
quality of a Sherline, MaxNC or Taig US made machine.

Another option might be to get a US made CNC mini mill for your precision
RC stuff and do the big stuff by hand on say the Grizzly G1005? Still,
that turbine would probably be hard to do by hand. You may also want to
consider a 4th axis rotary table. Generally, these make machining "radial"
parts much easier but you would need software that can handle a 4th axis if
want to go CNC. If it's a simple "2-D" turbine, you could use regular 3
axis CNC.

Mike