Michael Koblic wrote:
This is the cheapest milling machine I have seen so far:

http://busybeetools.ca/cgi-bin/pictu...3&NTITEM=CT133

Has anyone got some experience with it? Any comments on the specs? I suspect
someone will recognize it as an equivalent of a similar piece of Chinese
machinery sold in the USA under a different name (a game I have been playing
with mini-lathes recently :-)

I got mine for $495 (I think) on sale a couple
years ago. Since I have a Bridgeport, this was
for carting around to shows to show off my CNC
control gizmos. I wanted a "square" column, ie.
no round column that the head can swing around on
when raised or lowered.

It is not a great machine, but it does work, sort
of. The X-Y base is really not too bad, but 4" of
Y travel is a big limitation. The X axis has a
pair of ball bearings constraining one end of the
screw, but amazingly the Y axis just has a
shoulder of the screw pressing against the
bushing. This may work marginally for manual use,
but was a real problem for a CNC retrofit. I
bored the Y bearing block to accept a pair of
ball bearings, and it has worked amazingly well.

The spindle drive has plastic gears, and a top
speed of ~2000 RPM. For the kind of work you'd be
likely to do on such a machine, that is going to
be another limitation.
I could imagine doing a lot of work with 1/8"
carbide end mills, but you;d want more like 10,000
RPM for that. (But, I do the same thing on my
Bridgeport at 2720 RPM, so it can be done.)

Also, you REALLY want the R-8 version of this
machine, unless you already have a shop full of #3
Morse Taper tooling. Much more stuff is available
in R-8 that is almost impossible to get in Morse,
like stub milling arbors, slitting saw arbors, end
mill holders, fly cutters, indexable carbide end
mills, etc.

Yes, every tool supplier has this same machine,
often at a lower price (although it may have shot
up due to the recent financial turmoil).

I finally found a REAL use for this machine,
however! I converted it to CNC years ago, first
with steppers, then with servos, and took it to
shows for demos. One of the production parts I
make is a mounting plate for servo amps. Blanks
are cut from 1/8" aluminum, milled square and
bent, then they need to be drilled and tapped.
I had been using a Procunier tapping head on the
Bridgeport, and it works fairly well, but is an
incredibly long and wobbly assembly hanging about
11" out of the Bridgeport's quill. But, using
"thread drills" and the reversing drive in the
Procunier, it can drill, tap and retract the tap
in one smooth operation. Due to the way the
Bridgeport head is built, it is REALLY hard to fit
an encoder to the spindle to accomplish rigid
tapping. The mini-mill, however, has the top
bearing preload nut right on top of the head! So,
I fitted an encoder with index pulse to it and
adapted some timing pulleys to the spindle and
encoder. I then hooked up a servo amplifier to
the spindle motor, so it could be reversed under
computer control. Voila, rigid tapping on a $500
machine (with a few additions)!

See the bottom picture at
http://pico-systems.com/minimill.html for the
spindle encoder setup.

Jon