In article ,
Allan Adler wrote:
(DoN. Nichols) writes:
When you are through with this, *you* will be the person who
others are directed to when questions on the Unimat-1 are asked.
Oh, no, not that!!!! I had better rethink this....
:-)
Note that the Taig at least *used* to be offered with an
optional milling attachment.
I was hoping for something like that but the only thing I saw at the
Taig site was a separate milling machine costing a lot more than the
fully functioning lathe.
Because it needs one more axis of feed as a starter, thus one
more dovetail assembly, and more metal to give it all rigidity. Also,
the cheap or found electric motor which can be easily adapted to the
lathe is more difficult to use for the milling machine, because the
motor must be supported by the column with the milling head.
On the other hand, it occurs to me that if
some other company sells an inexpensive milling machine, say for around
$300, that might be a possibility, together with the no-frills Taig lathe.
Hmm ... let's look at the cheap Harbour freight milling
machines. I've seen them, and they are at least a major step up from
the Unimat-1 configured for milling. let's see -- there is the "Micro
Mill-Drill" for $279.99. Check out the URL:
http://www.harborfreight.com/cpi/cta...emnumber=47158
It is not much of a machine, but it is *far* beyond what you were
considering. It is also well beyond the capabilities of the Taig with
the milling attachment which I mentioned before, which itself is beyond
the capabilities of the Unimat-1.
Normally, I would suggest something even bigger, but bearing in
mind your stated limitations, this may be the best bet you have.
Beware that any milling machine or lathe will sooner or later
double your investment in accessories and supplies. Do you have any
precision measuring equipment, such as micometers? Those, at least, can
be time-shared between the mill and the lathe.
What do you think of the improvised milling machine shown at
http://members.rogers.com/lenwinn/mill_wlathe.html
He says it cost him about 300 Canadian dollars to modify the drill press
for this purpose, presumably including the vise he attached to it. I think
he means also including the cost of the drill press. I don't know what it
would cost now or what equipment would be needed to carry out this project.
It seems possible that he didn't need anything but the drill press to carry
out the modifications. Well, maybe he needed to tap some threads by hand.
It doesn't look to me as though he had to do any welding, not that I can
really tell.
Frankly -- it scares me. It is a combination of a cheap drill
press (with all the rigidity issues that involves), and a small X-Y
table with a vise mounted on it. Those tables are sort of reasonable
for placing holes at reasonably accurate location, but the side thrusts
involved in milling tends to rock the top of the workpiece on the rather
wimpy ways.
Second -- a drill press's quill is also not designed to take
side loads. The bearings are designed for thrust loads only. The quill
is usually rather sloppy in the head casting. (It looks as though he
has attempted to work around that by tightening a bolt threaded through
the side of the casting to press upon the side of the quill. (Look just
in front of where the hub of the feed levers attaches.
Third, a mill should be able to produce a fine feed of the
quill, and to lock it at a certain extension. It looks as though the
"locking" is accomplished by turning the stop assembly on the left
partially upside down, to press down upon the quill, instead of stopping
it at a preset depth. That bronze colored collar, with the white scale
wrapped around it, should be above the black arm, and is adjusted
according to the scale on the white sticker to the right of the threaded
shaft.
This lack of positive control of the quill position, let alone a
lack of a way to *lock* it in position, means that if a cutter starts to
dig in, as will happen on certain materials under certain conditions, it
will pull the end mill deeper into the workpiece, probably spoiling the
job.
Forth (and this would have been first, had he not found a
workaround) -- a drill chuck is *not* made for holding the hardened and
ground sides of an endmill, so the endmill tends to pull out. And the
chuck is normally attached to the spindle via a Jacobs taper, which is
excellent on thrust loads, but which is known to let go under side
loads, or loads which pull. Apparently, this one has a threaded
spindle, instead of a standard Jacobs taper to fit the chuck (making it
closer to a hand-held electric drill motor). And -- he has made an
end-mill holder to screw onto the spindle, thus reducing that particular
problem. This, he almost certainly made using the Taig you mention
below.
One final consideration is the diameter of the column. That is
rather small to be handling the loads involved in milling, and is likely
to flex and lead to serious chatter.
If you want to study modification of a drill press to make a
milling machine (sorta), go to google, and pull up a lot of dgoonz's
postings in this newsgroup from a few years back.
He also says he started off with a Taig lathe that he used for his
lathe work and milling. I'm not sure whether he is talking about
the attachment you mentioned or the milling machine he cooked up
out of the drill or something else, for example something like what
is described at:
http://easyweb.easynet.co.uk/~chrish/tmilling.htm
That one is talking about a milling attachment for a much more
solid lathe -- a Myford, which is a top-quality (and far from
affordable) lathe used by hobbists in the UK.
And even with that, it is rather limited in capability, compared
to a real milling machine. I would guess that the Myford with the
milling attachment is probably about as capable as the Harbor Freight
micro-mill indicated above.
P.S. The person who got the Micro-Mill that I saw, got it to
experiment with retrofitting it with CNC capability -- as he had already
done on a slightly larger mill-drill from the same source.
Good Luck,
DoN.
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