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In article ,
(DoN. Nichols) wrote:

In article ,
Joseph Gwinn wrote:
In article ,
(DoN. Nichols) wrote:

In article ,
Joseph Gwinn wrote:

[ ... ]

Instead, I'm thinking of getting a VFD that's big enough to run this
little 1/3 HP motor off one phase when I'm using the little drill press,
and this same VFD to run a larger 3-phase (probably a floor model) drill
press to be named.

Hmm ... you *do* know that *single* phase induction motors do
not start well (if at all) at anything other than their nominal
frequency? Typically, a 60 Hz motor can be started on 50 Hz and vice
versa, but run the frequency much up or down from there and you will
have problems. (A cap start motor could benefit from changing the cap
value depending on the frequency, but I'm not at all sure that it will
have much torque in any case.) I don't think that you can make this
usable at all. You won't have enough speed range to do you much good,
and you will always have to start it at the nominal frequency and then
adjust to what you want and see whether the motor stalls before you even
put any load on it.

I suspected there would be a problem, but can't say that I knew it.
This is why I tried the idea out on the group. At this point I'm
collecting ideas. And if I go the VFD with 3-phase motor approach to
variable speed, it won't cost me much to try it out on the little
1-phase drill press. I probably only need to be able to run at say 1/2
speed, and could have a run capacitor sized for 30 Hz.

Well ... try paralleling a second start capacitor of the same
value with the original one. This will only help with starting,
however, and I suspect that the torque needed to stop the spindle will
still be lower than you would like.

That's a good idea.

Running at half frequency (30 Hz versus 60 Hz) requires that the drive
voltage also be cut in half, to maintain constant flux density within
the motor. I don't think the running speed regulation is greatly
affected, but I suspect that the breakdown torque (where the motor
stalls) is cut in half compared to what it would have been had the motor
been wound for 30 Hz. The answer is probably documented in application
notes somewhere.

So the question will probably be how close to breakdown torque we are at
present. The mechanical variable-speed system drops the speed to 536
rpm for a motor speed of 1750 rpm, a 3.26:1 ratio. (These are measured
values, at zero load.) The torque at the chuck will increase by a like
ratio, and I have not seen the motor even laboring.

For the record, the ad copy claims 500 rpm to 3100 rpm, and I measure
536 to 2948 rpm (no load), so the ad copy is a bit optimistic. The
motor turns at about 1750 rpm, at the motor shaft.

So far, torque has not been the problem. If anything, the problem has
been that the chuck doesn't pinch the tool shanks nearly tightly enough,
so the chuck slips rather than the motor stalling or even laboring.

[ ... ]

I think I'll roughen the shank of the MA Ford countersink with flooded
wet-dry sandpaper. It really doesn't need to be polished.

I'm wondering if a better chuck would help. I looked at the
ball-bearing jacobs-style chucks, and at the more expensive keyless
chucks, such as those made by Rohm. Any opinions?
[snip]

There is a pecking order of cost and value, and I'm trying to find
something a bit better than what I have. Any ideas?

Hmm ... Can you find an ER collet adaptor with a MT shank to fit
your drill press? That, and a few selected collets might do the job for
you.

This is something to consider when I get the floor mount drill press,
but the cute little Delta DP350 has only the JT33 taper. I like the
size of the DP350 for many things, but in retrospect I'm not sure the
mechanical variable speed was that good an idea, although it sure is
convenient.

An alternative might be to simply get the tools you need with a
Morse taper shank to fit the drill press. I'm not sure whether a Ford
countersink is available with a MT shank, but you could check for it.
You might even call a good vendor like MSC (if you don't find it in
their catalog) and ask them. I've had them call the manufacturers for a
special at times -- and it wasn't *too* expensive. (I needed a
non-standard set of chasers for a Geometric die head for my turret
lathe.)

I know that for larger drill bits, I use MT shanks directly in
my drill press. (Though I've not had any problems with slipping chucks
in that one. It is a MT-2 spindle, with a Jacobs keyless chuck (akin to
the Albrecht in design and behavior). Granted, I did not pay new price
for that chuck, but lucked into a barely used one. I only had to get a
good arbor to fit my drill press spindle. Most of my other drill chucks
are Albrecht, with one Rohm (3/8" and quite good) and one Polish made
clone of an Albrecht (not as nice) in my bigger (12" swing) lathe
Tailstock. The key type Jacobs chucks are a real pain in a lot of
situations.

It pays to be lucky. So, the Rohm chucks are good. That's useful to
know. I assume you mean the Rohm keyless chuck. While the ball
bearing keyed chucks are better, they are still keyed.

No milling machine yet, for lack of a place to put it. Likewise lathe.
But soon. I'm slowly building my shop up, often on the debris of what
was once a vibrant machine-tool and manufacturing industrial base in New
England. Also, judging by what turns up on the used tool market, there
must be a lot of mechanics retiring and selling their tools by the pound.

Good Luck with that,

Thanks. I used to have access to a small machine shop and lived in
apartments. Now I have a wife and a house (now with a small workshop
area), but too far away from that machine shop. So, I'm seriously short
of iron toys, and a lot has changed over the years. At least the wife
doesn't mind the iron toys, even the noisy ones. But I don't think I'll
start a foundry operation.

Joe Gwinn