DIYbanter - View Single Post

In article ,
(DoN. Nichols) wrote:

In article ,
Joseph Gwinn wrote:
In article ,

[ ... ]

I looked at it this morning. It's a long shaft (~6 inches) with a long
keyway, plus two circlip grooves between which the variable pulley
mechanism sits, all metric. Definitely custom.

In another posting, Gunnar suggested machining an adapter shaft, which
could be done, but I don't know that I want to go to the trouble.

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.

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.

Stick a S&D drill bit, 1" or bigger, and the average VFD poops out
down there at low rpms, but simply change to the proper pulley size,
and fine tune your vfd and voila..a hogger.

The other problem I'm having is large drill bits and countersinks
slipping in the chuck. With the original keyed jacobs-style chuck, it
was not possible to get it tight enough by hand, so I used a six-inch
length of 3/8 black iron pipe as a key extender. This does work,
although the key arms were right at the edge of bending, or a little bit
over the edge, and the whole operation was pretty time consuming.

So, I bought a Phase II keyless 1-13mm chuck (Travers # 63-099-024, $32)
and it's a lot faster, but it too will slip on the larger stuff. I got
a surplus spanner wrench that allows me to hold the top (narrow) knurled
ring while hand tightening the body of the chuck, and this works for all
but the MA Ford 5/8 inch countersink (which has a very smooth shank).
There is noticeable added tightening when using the spanner.

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?

Note that Albrecht makes a keyless chuck with diamond
impregnated jaws, so they will grip on a hardened shank. I'm not sure
that you can find those with Jacobs taper sockets for an arbor for your
drill press. I think that they may be only in the "integral shank"
line, where you can get them with R8 shanks, or NMTB 30 or 40 or 50
shanks to go right into your milling machine.

It's a J33 taper, and Albrecht does make a diamond-impregnated keyless
chuck to fit (Travers # 63-005-558 for instance), and I've got to
believe that it would work well. But I'd feel a bit silly putting a
$326 chuck on a $200 drill press.

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?

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.

Joe Gwinn