Elliptical Turning?
Dan Bollinger
offset turning, but using an elliptical chuck. Using my homemade chuck I've
had some success, but chatter and vibration is a problem. I'm using small
scrapers and they work the best. I'm wondering if one of the fancy, new tool
designs for bowl turning might work better?
Australian Turner
I have used an elliptical chuck design and manufactured by John Rea in
Sydney Australia. I have used a 10mm (3/8") bowl gouge with no problem.
The secret is to cut at exactly the same height/axis to achieve a consistant
result.
Les
"Dan Bollinger" <danbol...@insightbb.com> wrote in message
news:QeaC8.251028$CH1.187556@sccrnsc02...
Dan Bollinger
begins to whirl around! How large a turning can you do with his chuck? How
much offset? Dan
Lyn J. Mangiameli
general, and those form eccentric turning in the specific, is available in the
form of the Kelton Balancer, to which you can attach you own eccentric chuck or
use the Kelton eccentric plate that can combine directly with the Kelton
Balancer. It will be a little while, but I've been conducting some experiments
with the balancer and will have a report on those and a review on the balancer
in several weeks.
If interested, you can find out more on the Kelton Website. The Wood-Tradesman
is one of the few stocking dealers I am aware for it in the US.
http://www.thewoodtradesman.com
Lyn
W.A. (Bill) Flowers
news:3CD96E33...@earthlink.net...
> It will be a little while, but I've been conducting some experiments
> with the balancer and will have a report on those and a review on the
balancer
> in several weeks.
Well, I guess we don't have to read the review now because you gave away the
conclusion in your first sentence. By your own words, the Kelton Balancer
is "an expensive, but very effective solution". :-)
--
Bill Flowers (a rather unbalanced guy)
Clearwater, FL
Dan Bollinger
chuck with an elliptical one. An eccentric chuck shifts the part off
center. An elliptical chuch shifts the center constantly, first to one side
of the centerline and then to the other side. Two translations per
revolution. So, a counterbalance won't work. It's forces act only once per
revolution. Dan
Lyn J. Mangiameli
I think there are many who would be thrilled if you were my copy editor. :-)
Lyn
Lyn J. Mangiameli
error, and doing so in such a pleasant and educational fashion. I'd love to see
some of your work.
Lyn
Donald Watland
an ornamental lathe. In this situation, the piece is held in an elliptical
chuck, on the spindle, but the spindle is turned VERY slowly, and the piece
is milled by virtue of a [rotary] cutter held in some sort of cutting frame.
The piece is not turned at a high speed and cut by a hand-held tool. Yes,
it is possible to spin a piece at a high speed on a regular lathe, held in a
special chuck that slides back and forth twice each revolution, using
hand-held tools, but this is essentially done by reckless and carefree.
Talk about undue vibrations and stress on the machine! Slip such a set-up
on a Jet 1236 (or equivalent), let 'er rip, and see how long the whole lathe
hangs together. Whee !!!!!!! Ride 'em cowboys !!!
Regards,
DW
"Dan Bollinger" <danbol...@insightbb.com> wrote in message
news:QeaC8.251028$CH1.187556@sccrnsc02...
Leo Lichtman
Dan Bollinger wrote:.... two translations per
> revolution. So, a counterbalance won't work. It's forces act only once
per revolution
Dan, your conclusion is right, but your reason is wrong. An elliptical
chuck moves the mass horizontally in simple harmonic motion. The frequency
is the same as the RPM of the lathe. To balance it, you need something
which produces simple harmonic motion in the same plane, at the same
frequency, and 180 degrees out of phase. A harmonic balancer meets
requirements two and three, but the forces are not confined to the
horizontal plane.
It might help some, thought, if your lathe is much stiffer against vertical
deflection than horizontal, which could very well be true, if the lathe is
bolted down.
If you wanted to build a balancer for an elliptical chuck, it would probably
have to look like a crankshaft--rod--piston assembly.
Leo Lichtman
Donald Watland wrote:... Slip such a set-up
> on a Jet 1236 (or equivalent), let 'er rip, and see how long the whole
lathe
> hangs together. Whee !!!!!!! Ride 'em cowboys !!!
Don, I have a Jet 1236. A couple of years ago I rented a video on how to
build one of these elliptical chucks out of wood. I wasn't even tempted.
Not only does it look dangerous--it's a lot of work to build, and who needs
it? You can buy oval picture frames at Woolworth's.
Rex Haslip
turning them does it
Rex Haslip
Auckland
New Zealand
"Leo Lichtman" <l.lic...@worldnet.att.net> wrote in message
news:%YjC8.13191$vT1.1...@bgtnsc04-news.ops.worldnet.att.net...
Dan Bollinger
size or as the ellipse ratio increases, so does the moment arm. Add some
rpm and you have a handful. Then again, it wasn't that long ago that the
same things were being said about 24" bowls! I turned a 24" punch bowl in
1975 outboard on a Rockwell HD 12" lathe. It was dicey for awhile, but low
rpms and sharp tools took care of everything. Dan
"Leo Lichtman" <l.lic...@worldnet.att.net> wrote in message
news:%YjC8.13191$vT1.1...@bgtnsc04-news.ops.worldnet.att.net...
>
Leo Lichtman
Rex Haslip wrote : You can also buy round wooden bowls there as well, but
that doesn't stop us
> turning them does it
Certainly not, Rex. My "flip" remark was made because it looks to me like
an awful lot of work for very little payoff. I would love to see an oval
turning that justifies the risk and effort. Maybe that's what Lyn has been
trying to get across to me in referring to the risk in art. (:-)
Also, I didn't realize they had Woolworth's in New Zealand <G>
Andrew Barss
: Also, I didn't realize they had Woolworth's in New Zealand <G>
Woolworth's went out of business in 1996, didn't it? Or did it just
relocate offshore? }:-}
-- Andy Barss
Dan Bollinger
>
> Dan Bollinger wrote:.... two translations per
> > revolution. So, a counterbalance won't work. It's forces act only once
> per revolution
> ************
> Dan, your conclusion is right, but your reason is wrong. An elliptical
> chuck moves the mass horizontally in simple harmonic motion.
point B)
>The frequency
> is the same as the RPM of the lathe.
Actually, it is double the rpm of the lathe since there are two movements
per revolution. In eccentric turning there is one per revolution.
>To balance it, you need something
> which produces simple harmonic motion in the same plane, at the same
> frequency, and 180 degrees out of phase. A harmonic balancer meets
> requirements two and three, but the forces are not confined to the
> horizontal plane.
Exactamundo!
> It might help some, thought, if your lathe is much stiffer against
vertical
> deflection than horizontal, which could very well be true, if the lathe is
> bolted down.
Always a good idea and a standard in industry.
> If you wanted to build a balancer for an elliptical chuck, it would
probably
> have to look like a crankshaft--rod--piston assembly.
Oops! You fell into the same trap as Lyn did. Such a mechanism could
balance one harmonic, but would actually double the other!
I have the advantage here. I've been thinking about this a lot since I want
to replace my homebuilt ellipse chuck with something heavier duty. Dan
Richard Peers
The only literature I've seen on oval turning is in David Springett's
book, "Adventures in Woodturning", where he describes how to build the
elliptical chuck, and then details several projects which use it. Yes,
the work-piece has to be smaller, to prevent the stresses that have
been described from becoming overwhelming - but sometimes I wonder
about the tendency towards ever-larger turned items which sometimes
gets referred to on the group (a bit like Ruth and her "aggressive
turners"). The smaller pieces can be just as challenging, if not more,
especially miniatures where the tightness of the grain becomes a real
issue.
There is also a video by David on the same topic, which might well be
the one referred to elsewhere in the thread.
Yes, the same effect can be achieved with a router, or carving tools -
heck, if you work at it long enough with abrasives you could probably
get a good result, but we are turners, so that's the way we like to
shape our wood ;-)
It would be nice if some enterprising manufacturer were to produce a
metal version of the oval chuck, which would no doubt be less prone to
vibration damage - but the extra weight could shake the lathe worse,
so this may be a blind alley.
Oh, and for Leo's benefit, Woolworth's is still going strong in the
UK...
Richard Peers
Webmaster, East Surrey Woodturners
http://www.eastsurreywoodturners.org
Home of the Woodturning FAQ
"Dan Bollinger" <danbol...@insightbb.com> wrote in message news:<kCPC8.10184$Po6...@rwcrnsc52.ops.asp.att.net>...
Fred Holder
allows higher speeds with out the vibration. Currently, Vicmarc in Australia is
working on bringing this chuck to production. Johannes has written several
articles for More Woodturning on the subject of oval turning. At this time, I
have no idea when Vicmarc will have the chuck available for production or what
its cost might be.
Fred Holder
<http://www.fholder.com>
In article <bfebe360.02051...@posting.google.com>,
richar...@hotmail.com says...