Don Foreman wrote:
On Mon, 22 Mar 2010 21:37:42 +0100, Tom Ivar Helbekkmo
wrote:


Need some advice, here...

I occasionally wish I had a small mill, but can't really afford to go
out and buy one. I was going to modify my 7x14 mini-lathe to accept a
small vertically mounted vise where the tool holder normally goes, in
order to use it for the odd milling operation.

Then, a local company started selling these:

http://www.wddm-machine.com/pro_show.asp?ID=51

That is, the one on the left, the WDM ZX7016. A better pictu

http://www.jula.no/bore-fresemaskin-125693

Click the magnifying glass in that picture for a large version.

It costs about a third of what importers charge for a typical mini-mill
over here. Now, I know it's just a sturdy vertical drill with an X/Y
table, but it does feel really solid and stable (it weighs 165 lbs
without the stand shown in the picture), and even if I don't lock the Z
axis, I can't detect any slop whatsoever in the quill, even when cranked
all the way down.

I'm sorely tempted. However, I notice a couple of details that I'm
unsure of. The spindle taper is MT2, whereas it seems most tooling
offered out there is R8. The importer does supply a nice looking collet
chuck in MT2, though. Possibly worse: I'm wondering if I'm going to be
cursing that table every time I use it, because it lacks a central T
slot...? It seems to me every picture I see of anything at all mounted
on a coordinate table uses the center slot, which someone must have
plain forgotten to draw when the plans for this mill were made.

-tih


Morse taper is fine for drilling, unacceptable for milling unless
there's a drawbar to hold the cutter firmly in place.

This would make a decent small drillpress, and a rather poor mill, as
you correctly surmise. Still, if the price is right, it would probably
be better than a milling attachment in a small lathe. I also agree that
a drawbar is essentially REQUIRED. I've seen a few similar small
mill-drills (drillpress based) ... most have had some kind of drawbar
.... perhaps 'wimpy', but probably "OK" for such a small machine.

A Morse taper alone will not hold adequately for most milling unless
seated FAR to tight to get out easily. A few early mills used only a
Morse taper, sometimes with NO drawbar. It was a bad idea, but worked,
sometimes, maybe. Even when the taper is properly seated, an interrupted
cut can work the cutter loose. That's NO fun at all! You REALLY want a
drawbar.

While much harder to find, and likely more expensive, than R8 tooling, a
fair selection of M2 Morse Taper tooling is available (drill chucks,
collets, endmill holders, boring heads, flycutters, slitting-saw arbors,
etc.). I think any you find today will have a threaded socket for a
drawbar, usually 3/8" (at least in the "English" world).

I have a little BenchMaster horizontal/vertical mill that uses M2 tapers
and a 3/8 drawbar. It's completely satisfactory for it's size. The only
issue with the M2 taper is that, once a tool is seated with the drawbar,
it often takes a pretty good WHACK on the drawbar to unseat it. Morse
tapers are said to be "self-locking", while R8 tapers are
"self-releasing" (both, sort-of). Such a jolt can't be the best for the
spindle bearings, but really has caused no problems in many years of use.

Dan Mitchell
============

--- news://freenews.netfront.net/ - complaints: ---