I'm trying to rough the outside so I'm not grabbing the bowl by a cut tenon
on one side (I'm trying to create the tenon as well!) but I'm trying to spin
the blank between centers to get a good round shape. I've done one blank
which turned out well and made the tenon (need to procure a chuck next!) to
hold in the chuck. But I've also noticed that the top and bottom are not
parallel. Not that much of a biggie as I'll turn the one side flat, but
this new blank wobbles so much and I'm trying to find the best way to center
it between the centers.

I am rounding out the blank initially on the bandsaw, but man does this
thing make the lathe wobble. I'm using a Jet mini lathe.

Thanks in advance for any help!

--

Mike

"Mike Rinken" wrote: (clip) this new blank wobbles so much and I'm trying to
find the best way to center it between the centers. (clip) I am rounding
out the blank initially on the bandsaw, but man does this thing make the
lathe wobble. I'm using a Jet mini lathe. (clip)
^^^^^^^^^^^^^^
The Jet mini is not a heavyweight, so you have to run slow, and try to get
the blank in pretty good balance from the start. Assuming you are mainly
trying to find a centerline that minimizes vibration, here is something to
try: slip the drive belt off, so the spindle is free to rotate. The heavy
side will go to the bottom. Shift the spur drive and/or live center until
the blank does not have a heavy side. Then put the belt back on and
proceed.

First off, I usually use a faceplate and live center for that
operation, not two centers. It's easier to get the blank positioned
properly, but takes a little more time. Build yourself a giganto-spur
by sharpening three or four machine bolts to a point, and bolting them
to your faceplate to form a three- or four-prong spur. As they'd be
further apart, they'd just naturally force the flat parallel to the
faceplate.

Second, I think it's expected that you'd turn the blank by hand and
see if it's doing what you want before turning on the lathe. Some
adjustment might be needed. As you turn it, see where the edge of the
flat part (drive center side) pass by the toolrest; if they all pass
at the same spot it will be close to parallel.

Third, I often use a Dewalt powered plane to carve the blank a bit
after it's mounted, to get it more balanced. This is after the rough
carving-to-shape with a chainsaw. FYI: for reeves drive, it's easier
to hand-balance the blank if you set the lathe to the FASTEST speed.
That gives the spur a mechanical advantage over the motor, and thus
reduces "friction". Remember to slow it down again before spinning up
the blank for real. If you have step pulleys, just take the belt off
or de-tension it.

"Mike Rinken" wrote in message
news:ljGed.308438$3l3.33866@attbi_s03...
I'm trying to rough the outside so I'm not grabbing the bowl by a cut
tenon
on one side (I'm trying to create the tenon as well!) but I'm trying to
spin
the blank between centers to get a good round shape. I've done one blank
which turned out well and made the tenon (need to procure a chuck next!)
to
hold in the chuck. But I've also noticed that the top and bottom are not
parallel. Not that much of a biggie as I'll turn the one side flat, but
this new blank wobbles so much and I'm trying to find the best way to
center
it between the centers.

I am rounding out the blank initially on the bandsaw, but man does this
thing make the lathe wobble. I'm using a Jet mini lathe.
===========================
Mike,
If you're using pre-cut square blanks, draw a diagnonal line line from
corner to corner on both sides. Where the lines intersect will be the center
for each side. Place your drive spur on one center and the live center on
the other side. You can draw a circle using the center point to use for a
guide for cutting with the band saw.

If the pieces aren't square, cut some circles out of plastic, cardboard, or
hardboard (Masonite or equavilant). Make these with increasing diameters in
the range you expect to be turning (i.e., 3-10 inches, 1/2 in. increments
are good). Use these as templates for your bandsaw cuts. These blanks should
be close enough in balance to start at the slowest speed on your lathe for
rounding into better balance.

If you have varying densities inside the wood, or voids, you may have to
manually balance before your 1st cut. Suspend the piece loosely between
centers; allow it to rotate to its natural balance, the low side will be
heaviest. Raise slightly and repeat until you no longer have a "low" side.
That should be near you balance point for turning.

Ken Moon
Webberville, TX.

Mike Rinken wrote:
I'm trying to rough the outside so I'm not grabbing the bowl by a cut
tenon on one side (I'm trying to create the tenon as well!) but I'm
trying to spin the blank between centers to get a good round shape. I've
done one blank which turned out well and made the tenon (need to
procure a chuck next!) to hold in the chuck. But I've also noticed
that the top and bottom are not parallel. Not that much of a biggie
as I'll turn the one side flat, but this new blank wobbles so much
and I'm trying to find the best way to center it between the centers.

I am rounding out the blank initially on the bandsaw, but man does
this thing make the lathe wobble. I'm using a Jet mini lathe.

Thanks in advance for any help!


Thanks for all the great advice. I've gotten better at finding the "center"
on both sides and improved my method this weekend. The blanks I got we're
from Rockler and all 6 turned out well once I started getting them in shape
on the lathe. I actually clamped the lathe to my workbench and that took a
lot of the vibration out. I also cut the tenon on the bottom for the chuck
and then decided to cut a tenon on the top to flatten it out now that I had
turned a center and that obviously dampened it down.

Now I just gotta get a chuck!