jc

There's another answer to your question and that is, balance the work
carefully BEFORE you turn on the lathe.

I turn a lot of bowls (on a Jet 1442 by the way). When I take a slab of
tree that's 13" or so in diameter, and 9-10" deep that's a respectable
weight. If it's eccentric it can make that 200# or so pound lathe dance.

What I learned to do, by trial and terror, was to balance the wood BEFORE I
started to turn it. First, I cut off any stuff that makes my skin crawl,
like branch protrusions or other sharp corners that would otherwise need to
be turned off. I put pointed centers in the head and tail stocks, and stick
them into the wood where I think the center is. Only the points penetrate
the wood, so it will pivot on them.

Of course the wood isn't exactly centered and it revolves so that the heavy
part is at the bottom. (Thank goodness for gravity). I then raise the wood
just a bit at one end, and stick the point in, again. Again the wood shows
its unbalance. I keep doing this until the wood will twirl when spun by
hand, without stopping at a particular low point. Then I crank in the
tailstock to make the correct holes deeper than the trial ones.

I take the wood off, and hammer the drive center into the wood, and make a
deep indentation for the tail center. If the wood has bark or
irregularities where the center should go, I use a brace and 1" bit to give
me a good flat surface with a hole for the center.

Its rather impressive to see a 30 to 40 pound irregular piece of wood
spinning at 450
RPM's and the lathe is only gently vibrating.

I've opted not to load the base of my machine with sand or concrete blocks,
on the theory that if I have a load that is so unbalanced that the lathe is
chasing me out the door, it's putting a HELL of a strain on the bearings,
and on the wood where the centers fasten it to the lathe.

Finally, I have learned NOT to start roughing the wood from the side, where
each corner is whacking the chisel 7 times a second. I go at the tail
end--I think that was Darrell F.'s suggestion on his web site. Two
reasons--first I'm standing out of the throw zone, and second the wood near
the center is moving MUCH slower. I start my cut there, and work my way
slowly out towards the edge. That way I've always got a surface (maybe not
a continuous one, but a surface where I'm cutting) that supports the chisel
when it's cutting the wood. Small bites, sharp chisel, and it really goes
well.

And, I have learned to hold the chisel lightly, and anchor it to the tool
rest, so that if the lathe and the work do vibrate a bit, the chisel is
moving right along with the wood, so the cut stays smooth and the chisel
doesn't gouge into the wood and catch. It doesn't take long to turn away
the eccentric spots and get a smoothly running blank.

Sorry to go on for so long, but I'm rather pleased with how easily I do it
now, compared with the high pucker factor turning I was doing earlier.

Old Guy




"Joe" wrote in message
. net...
Is there are formula or rough correlation for a starting (roughing down)
speed as it relates to the diameter of the piece being turned? What do
you use? I have a Jet 1442 (reeves) and if it means i can't safely turn a
piece on its lowest speed, I'll have to make a design change.

I know there are many factors to consider here, including balance of the
piece being turned, I'm just looking to see if my lathe's low end is in
the neighborhood.


Thanks,

jc