On 2014-01-23, wrote:
I figure some of you out there must have done this before!

I just got an Optimum D650 lathe (see link 1), and I?d also like to
have a 12? disc sander in my shop, but in my country (Germany) they are
quite expensive, even used. I?m thinking of trying to kludge one on to
back of the lathe, and mount a tilting table to the back cover (see link
2). This would save space, and I?m not that busy at the moment.

My first question is "can your lathe produce sufficient speed for
a sanding disc to work well?". It looks as though your maximum RPM is
2200. Normally, the speeds are significantly higher. Is that 12 inch
diameter? I see a '?' with my system where I would expect a '"' for
inches. Did you compose this with a web browser? On Yahoo, I suspect
so. Spell out units if using a web browser, as they tend to install
weird characters which won't work with a plain text newsreader or e-mail
client.

Second -- how are you going to keep the sanding dust from
rapidly abrading the ways of the lathe? I would put a disc sander as
far as possible away from the lathe or any other precision machine
tools. The grit from the sanding disc is *very* bad for the ways.

And -- another safety point brought on by your photo of the
lathe itself. *Never* leave the chuck key in the chuck -- even just for
a photograph. If you hit the power switch, that chuck key gets thrown
at a rather impressive velocity -- assuming that it does not simply slam
into the ways of the lathe, damaging them.

The biggest problem is that the end of the spindle is not threaded,
and there?s not much to attach to back there. My idea is to mount the
disc plate to a long rod which goes all the way through the spindle bore
and is then held by the chuck. Since the spindle bore is only 26mm, I?d
need to make some sort of adapter ring to make everything stable (See
drawing ? link 3). I feel like this should work, if a bit quixotic. Any
ideas on whether or not I?m on the right track, or if there would be
another way to attach the disc to the spindle? Ideas on the tilting
table? I'm planning on doing everything with aluminum, since I don't
have a milling machine.

Is the lathe large enough to turn a 12 inch disk of aluminum?
You'll have to saw it to something a bit oversized and turn it down.

Also -- does it have the horsepower to proerly turn a 12 inch
sanding disc at the maximum speed which it can achieve.

Anyway -- I would turn a plug which would just barely fit into
the open end of the spindle, then drill most of the way through and tap
for a large setscrew (say 1/2 inch or so (or 13 mm or so), with a cone
point), and then using a hacksaw or bandsaw if you don't have a milling
machine, cut through the diameter on the inside end twice -- the second
at 90 degrees to the first. At this point, when you run the setscrew
into the center it will eventually hit the bottom of the drill hole and
expand the plug to grip it firmly into the spindle.

To this you will bolt your 12 inch disk. (Actually -- do this
bolting before you turn the disk to diameter, so it will be concentric.

Since I must regularly open the cover to change speed and feed rate,
the whole business must be easy to remove.

If you punch a hole in the center of the sanding disc (which is
moving too slowly to be of use sanding anyway) you can reach through
there with the Allen (hex) key to loosen the setscrew and pull off the disc.

The cover is fairly beefy, so
I think with some reinforcement bars I can mount a table which would
work well enough.

Again -- I would not put sanding operations this close to the
precision machine surfaces.

Better to go ahead and make the disc and hub (without the
expanding split grip I described above) and get a used electric motor of
adequate size and bore the hub to slip on the end of the motor shaft.
Get at least a 3600 RPM (really marked something like 3450 RPM or so)
and I think at least a 1/2 HP motor for that large a disc -- and more
likely a 1 HP motor. (In Germany, probably marked in KW instead of HP,
figure about 0.750 KW is about one HP.) Sorry for the inch figures, but
I *think* you used inches for the diameter of the sanding disc, anyway,
even though the ID of the spindle is just slightly over 1" (25.4 mm).
:-)

If you can't get a motor faster than about 1750 RPM, then plan
to add a pair of pulleys and a belt to increase the speed. Mount the
motor below a workbench, and the disc above it, so the weight of the
motor can put tension on the belt.

Drill the hub underized, and use a boring bar to enlarge to a
slip fit on the motor shaft -- a drill bit will typically be oversized.

Thanks for all constructive replies. Please no safety warnings!

Sorry! Already typed the one about the chuck key. And I could
not let that one go unremarked, anyway.

Also,
no. I don't have to worry about voiding my warranty. The machine is
twenty years old!

But you *do* have to worry about abrading the accuracy out of the
bed.

http://i389.photobucket.com/albums/o...ps3e4545f7.jpg

http://i389.photobucket.com/albums/o...ps9c7b821c.jpg

http://i389.photobucket.com/albums/o...ps89a0f1b9.jpg

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---