DoN. Nichols wrote:
According to :
Can anyone elaborate on the differences between a Drill and a Mill as
far as the relative size, placement, and materials when it comes to the
chuck, spindle, quill, arbor, collet, bearings, gears, ect.?

In other words, it's obvious that a mill can move the tooling along
more than a single axis, unlike the drill press, but I am attempting to
get a handle on the *physical* reasons why so many here say that a
drill press shouldn't be adapted to mill use.

Start with the lack of rigidity of the drill press's frame. It
is designed only to support the workpiece against the axial forces of
drilling.

A milling machine has a *lot* more metal in the head, a more
rigid column (the best ones don't have round columns, and actually move
the *table* up and down with a leadscrew. Even those with round columns
have a larger column diameter, to minimize the twist under cutting loads.

The quill (which moves the spindle up and down for drilling type
operations) is larger in diameter, and a more precise fit in the
headstock, so it will not move sideways under cutting loads.

The mounting of the cutter to the spindle of a milling machine
is *not* via a drill chuck. A drill chuck is normally mounted via a
taper -- a mount not designed for side loads, as the drill chuck will
pop lose and start bouncing around the shop, spinning rapidly, and
carrying a sharp cutter with it.

And -- a normal drill chuck is not designed to grip the hardened
surface of an end mill shank. (An exception is the diamond grit jaws on
one of the more expensive Albrecht drill chucks -- designed for use in a
milling machine, and made with a standard milling machine taper (e.g.
#40 MTMB, or R8 collet format) shank -- *not* a taper such is used for
normal drill chucks.

The bearings in a drill press are designed to handle only the
axial (thrust) loads, not side loads.

If these physical reasons can be solved with only small manufacturing
changes in drill presses to allow them to become more suited for
milling, then does the conventional drill presses unsuitability have to
do with the bottom line of the manufacturers or lack of consumer
interest responsible for a lack suitable adapers/tooling, or perhaps
there are other logistical issues involved?

I've heard about the specific forces that the bearings and so forth
would have to take as being a reason for a drill presses unsuitability
for milling operations, but it seems to me that a suitable gearing
adapter would negate much of these "lopsided" forces.(Probably at the
expense of a lot of power).

Gear drives can increase the torque at the expense of speed. So
can belt drives. This is *not* the major weakness of a drill press when
used for milling.

Milling machines have a *lot* more steel and cast iron which go
into their makeup.

There are cheap small tabletop drill presses which can be easily
lifted with one hand. The weight of a tabletop milling machine of
similar size will probably require a two-hand lift.

Also, I figure that since so many of you have been machining for so
many years, is there a possibilty that any bad drill press milling
experiences are at least in part a result of a lack of availability of
suitable adapters and tooling for this?

A lack of suitable design for the purpose. A *first*
requirement for a drill press which is going to be used for milling is a
hollow spindle, so a drawbar can lock the end mill holder or collet into
the spindle -- to protect against popping the tool holder out from side
loads.

And *nobody* is going to make a drill press with such a spindle,
as it would cost more, and the machine's frame would still be inadequate
for the lateral and twisting loads which milling would apply to it.
Making a drill press with such a spindle would simply be leaving them
open to lawsuits, which all manufacturers would rather avoid at all
costs.

Note that a radial arm drill press *might* be solid enough in
some features so you could get away with it -- but none of these weigh
less than a minimal floor-standing milling machine, and there is no way
that you could get it up to your apartment.

Anyway, in the meantime I will of course still take the advice of not
using a drill press for milling purposes, but only when it comes to
metals, because there shouldn't be as much of a problem with plastics
like Nylon or Delrin.(But I'll listen to opinions either way). :-)

Of course there are problems using it for Nylon or Delrin. You
have done nothing to deal with the tendency of the chuck to pop off the
taper when subjected to side loads.

And there is still the tendency for the frame to wind up under
cutting loads, causing a deeper cut than you intended, and thus
increasing the chance that the chuck will pop off.

Yes -- it is *possible* to redesign and manufacture a drill
press for use as a milling machine -- and this is exactly what you will
get if you purchase a "mill drill". And -- it will be to heavy to get
up your stairs. (And -- it will still not have the workpiece size
ability of a milling machine so designed from scratch.

To clarify what I said about the specific(radial) forces not friendly
to the conventional drill press, I was addressing the possibility of a
"gearbox" placed *after* the chuck that would negate these negative
forces to an extent.(That is why I said that it would result in the
loss of a lot of power, by virtue of being inefficient). This gearbox
would of course have to be made to "fit" the housing in the chuck area.
This would have the effect of distributing out the radial loads that
account for all the negative things you mentioned. But of course there
is still the ridgidity issue.

P.S: I haven't been able to find detailed plans on the internet, so if
anyone is aware of any illustrated info concerning the parts and
dimensions of these machines, and in particular the work tables(rotary
and otherwise), I'd appreciated it.

Thanks a lot.

Darren Harris
Staten Island, New York.