"nuk" wrote in message
...
Hello,

What is the difference btwn a 'mill' and a 'mill-drill'? I presume a
'mill' is a vertical mill such as I can find in Enco or Grizzly or other
importer's catalogs... and I have a fair-to-middlin' idea of what a
drill press is... so what distinguisheds a 'mill-drill' and what are
the pros and cons of one?

A mill is what a mill-drill tries to be. Typically, a milling machine is
much heavier, much stiffer, and generally more precise. There may be
additional features on mills that are typically not available on
mill-drills. Most mill-drills have only a quill feed for the vertical
direction -- like a drill press. By contrast, a vertical milling machine
typically has a knee that can lift the entire table up in addition to the
quill feed. Other possible differences include the ability to zero-set the
various dials, to adjust the gibs, to lock the motion in any of the three
axes, power feed, speed ranges, etc. A mill-drill will not be able to do
the heavy-duty precision cutting that a true milling machine can. For a
hobbyist, some of these differences may not matter.
There is, however, a key difference between the two machines.
Mills use collets, such as R8, 3C, B&S, and other collets and special end
mill holders, arbors, etc. The typical mill-dril, like drill presses, has
a Morse (#2 or #3) taper spindle. That spindle is not designed to take
significant side load. It is designed to take load in the direction of the
spindle axis. Collets and tooling (e.g., tool holders, arbors, etc.) are
also available for Morse taper tools. Now for the most important
difference. What holds the collets in? In milling machines, the collet is
held in place by a drawbar that screws into the back of the collet and
therefore pulls the collet shut and tight. Some mill drills have a drawbar
for the collets. Some do not. A mill drill without a collet drawbar, in
my opinion is not much better than a drill press with a good XY table. The
end will will, under any significant load, screw into the work and thereby
pull the entire collet out of the spindle. This is the main reason why
milling on a drill press is so limiting. I would reject any mill-drill that
did not have a collet drawbar.

Boris

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