Store-bought eccentric and multi-axis chucks are expensive. I've never
used one, but I understand that they work well and are easy and precise
to use. My cobbled messes work to a degree, but commercial chucks are
probably much more useful and convenient for changing eccentricity or
shifting axes in measured steps, plus being able to return to any one
step. BUT, some cost more than a quality mini-lathe!

My eccentric chucks are nothing more than a machinist faceplate with a
radial slot for a dog. I used a shortened pipe tap moved along the slot
to hold the blank and vary it's eccentricity. I can drill an accurate
hole in a blank for a tap much easier than I can turn an accurate tenon
for a die, but either a hole for a tap or a tenon for a die allows for
_cutting threads. Much better for securing wood than the crushed threads
made with a bolt or the headstock spindle. I also used a tailstock
center or a rotating backing plate when possible.

I've sharpened and ridged the jaws of an independent 4 jaw wood chuck.
Adjusts and holds pretty well for eccentrics. I've also slit a 2.5 in.
length of 2 in. pipe into 4 sections and inserted them into the 4 jaw
chuck as deep 'jaws'. I can round the end of a blank and move it off
the spindle axis and hold it there in these 'jaws' or in a scroll chuck
with deep jaws. Adjustments are limited and a pain to make. As for
precision, forget it. It's true, "You can't go home again" nor can you
go back to a previous axis with this set up.

I've thought about scribing concentric lines on a face plate and
drilling holes on the lines , but scattered about the radii so they
don't overlap. A screw or small tap could be attached to the various
holes for holding the blank on different eccentric axes. Seems like a
lot of messing about with imprecise adjustments.

Sorry for my tedious and confusing description. Do any of you have (or
can suggest) other cheap homeshop chucks or methods for holding a blank
on variable axes with convenient and fairly precise adjustments. If so,
how do those of you bereft of pricey factory chucks do it?


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Arch you've been reading my mail :-))
I am about to turn some oval door knobs for a stage set using forced
perspective. Each knob gets smaller the farther away from the
audience. So far I have come up with just using 2 jaws in a 4 jaw
scroll chuck. I cut a rectangular tenon on the end of each piece so
that I can slide it in the jaws and allows me to mark the centres with
a sharp pencil along the edge of the jaws. Tun between centres with
the same offset each end then move onto the new centre and so on. So
far so good. I kind of got the idea from Ken Grunke's eccentric chuck
here http://www.token.crwoodturner.com/ecc/
For more on forced perspective see here http://studiochalkboard.evansville.edu/r-theatre.html
Peter
Visit my site at:
http://www.oldtoolsshop.com/Galoots/pHyde/

Hello Arch,

Sounds like you've sort of run the gamut of home made ways to cobble
up for eccentric turning. As a renouned tool-a-holic, I own most if
not all of the eccentric chucks on the market and only a couple of
them let you go back to an exact previous setting.

I have also turned faceplate work eccentric by using multiple holes
and a screw chuck faceplate into a glue block on the workpiece. You do
have nearly precise return to previous positions, but your offset
can't be to excessive or you will tear out the screw threads in the
wood. If possible one should use the tailstock to help support wood
like this.

I have at times used my Nova Chuck with the 35 mm tenon jaws, which
have serrated teeth inside the jaws, to do eccentric turning for
goblets, etc. You have fair control of the amount of eccentricity once
you have clamped it down onto a tenon.

I do more oval turning of hammer handles between centers and have
demonstrated that locally and in Australia and New Zealand many times,
but have only made one oval hammer handle for an actual hammer(which
was for my wife's hammer when she broke the handle and wanted one out
of Lignum viate).

Each of the commercial eccentric chucks have their merit. My first one
was the Robert Sorby Eccentric Chucks, which shifts the wood sideways
with a rotating eccentric disk that the wood is mounted to. I've since
purchased the Escoulen ball and socket chuck, the Axminister eccentric
chuck, one that is made by a fellow in England with different mounting
holes (can't remember the name at the moment), and for Christmas 2005
my wife purchased the new Escoulen chuck which combines the ball and
socket with the portion similar to the Robert Sorby chuck. This thing
has many more adjustment options than I have imagination. I covered
all of these except this last one in my book, "A Guide to Work Holding
on the Lathe", which is available from Amazon.com.

I hope this rambling adds to your discussion.

Fred Holder
http://www.fholder.com

On Apr 4, 2:55 pm, (Arch) wrote:
Store-bought eccentric and multi-axis chucks are expensive. I've never
used one, but I understand that they work well and are easy and precise
to use. My cobbled messes work to a degree, but commercial chucks are
probably much more useful and convenient for changing eccentricity or
shifting axes in measured steps, plus being able to return to any one
step. BUT, some cost more than a quality mini-lathe!

My eccentric chucks are nothing more than a machinist faceplate with a
radial slot for a dog. I used a shortened pipe tap moved along the slot
to hold the blank and vary it's eccentricity. I can drill an accurate
hole in a blank for a tap much easier than I can turn an accurate tenon
for a die, but either a hole for a tap or a tenon for a die allows for
_cutting threads. Much better for securing wood than the crushed threads
made with a bolt or the headstock spindle. I also used a tailstock
center or a rotating backing plate when possible.

I've sharpened and ridged the jaws of an independent 4 jaw wood chuck.
Adjusts and holds pretty well for eccentrics. I've also slit a 2.5 in.
length of 2 in. pipe into 4 sections and inserted them into the 4 jaw
chuck as deep 'jaws'. I can round the end of a blank and move it off
the spindle axis and hold it there in these 'jaws' or in a scroll chuck
with deep jaws. Adjustments are limited and a pain to make. As for
precision, forget it. It's true, "You can't go home again" nor can you
go back to a previous axis with this set up.

I've thought about scribing concentric lines on a face plate and
drilling holes on the lines , but scattered about the radii so they
don't overlap. A screw or small tap could be attached to the various
holes for holding the blank on different eccentric axes. Seems like a
lot of messing about with imprecise adjustments.

Sorry for my tedious and confusing description. Do any of you have (or
can suggest) other cheap homeshop chucks or methods for holding a blank
on variable axes with convenient and fairly precise adjustments. If so,
how do those of you bereft of pricey factory chucks do it?

Turn to Safety, Arch
Fortiter

http://community.webtv.net/almcc/MacsMusings

I have built a couple of vacuum chucks that allow for a variable axis. I
got the idea after watching a demo by Escoulen. His chuck holds the wood in
a ball and socket clamp, causing the spindle end to stay on axis, while the
other end orbits. The axis flies around on a conical path.

The first chuck I built had a convex spherical surface, and vacuum, so the
wood could be moved off axis just like his. However, I made a change which
I think is actually better than his. I changed the convex spherical surface
to a concave one. This means that as the wood is moved off axis, the cone
faces the other way. The end that is orbiting is close to the chuck, and
the tip of the cone is on axis near the tail stock. This means that I can
turn an off-axis piece with both ends securely held.

I never got as far as providing for indexing the piece, but I think it could
be done fairly easily by making circles and degree marks on the spherical
surface.

In case you are wondering, I attach the blank to a bowl-shaped piece, and
stick that to the vacuum chuck.

Arch wrote:
Store-bought eccentric and multi-axis chucks are expensive. I've never
used one, but I understand that they work well and are easy and precise
to use. My cobbled messes work to a degree, but commercial chucks are
probably much more useful and convenient for changing eccentricity or
shifting axes in measured steps, plus being able to return to any one
step. BUT, some cost more than a quality mini-lathe!

My eccentric chucks are nothing more than a machinist faceplate with a
radial slot for a dog. I used a shortened pipe tap moved along the slot
to hold the blank and vary it's eccentricity. I can drill an accurate
hole in a blank for a tap much easier than I can turn an accurate tenon
for a die, but either a hole for a tap or a tenon for a die allows for
_cutting threads. Much better for securing wood than the crushed threads
made with a bolt or the headstock spindle. I also used a tailstock
center or a rotating backing plate when possible.

I've sharpened and ridged the jaws of an independent 4 jaw wood chuck.
Adjusts and holds pretty well for eccentrics. I've also slit a 2.5 in.
length of 2 in. pipe into 4 sections and inserted them into the 4 jaw
chuck as deep 'jaws'. I can round the end of a blank and move it off
the spindle axis and hold it there in these 'jaws' or in a scroll chuck
with deep jaws. Adjustments are limited and a pain to make. As for
precision, forget it. It's true, "You can't go home again" nor can you
go back to a previous axis with this set up.

I've thought about scribing concentric lines on a face plate and
drilling holes on the lines , but scattered about the radii so they
don't overlap. A screw or small tap could be attached to the various
holes for holding the blank on different eccentric axes. Seems like a
lot of messing about with imprecise adjustments.

Sorry for my tedious and confusing description. Do any of you have (or
can suggest) other cheap homeshop chucks or methods for holding a blank
on variable axes with convenient and fairly precise adjustments. If so,
how do those of you bereft of pricey factory chucks do it?


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Arch ... you got some links to pics I could look at?

Grunke's faceplate / wormscrew arrangement looks nice.

--
http://nmwoodworks.com/cube


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Hi Bill

Get the coffee on, here's a few looks and info.

http://homepage3.nifty.com/manasan/e...rning/turn.htm

http://home.vicnet.net.au/~pwguild/o-rosego.htm

http://www.robert-sorby.co.uk/press-...-eccentric.htm

Have fun and take care
Leo Van Der Loo


On Apr 5, 12:44 am, Bill in Detroit wrote:
/snip
Arch ... you got some links to pics I could look at?

Grunke's faceplate / wormscrew arrangement looks nice.

--http://nmwoodworks.com/cube

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On Wed, 4 Apr 2007 18:55:50 -0400, (Arch) wrote:

I've thought about scribing concentric lines on a face plate and
drilling holes on the lines , but scattered about the radii so they
don't overlap. A screw or small tap could be attached to the various
holes for holding the blank on different eccentric axes. Seems like a
lot of messing about with imprecise adjustments.

Hi Arch-

If you like, I could program and run you one of these if you've got
some specs in mind. Setting my machine to run it while I'm at lunch
and would otherwise be idle wouldn't be much trouble at all, and I
could get those holes located for you to within .001". Also, after
seeing the thread on the Longsworth chucks from a while back, it has
given me plenty of interesting ideas.

For instance, if you wanted finer adjustment, I don't imagine it would
be too much trouble for me to draft and cut a spiral slot in a disk
with periodic etched marks to use as reference points for your various
axis. A tight spiral could produce very fine increments of
adjustment, but there is a limit to how much material could be removed
before the disk becomes too weak, and unsafe to use. I'd imagine that
one time around the disk, going from near the center to somewhere near
the outside edge would be pretty useful, though.

Let me know if you want to look at this more closely, and we'll take
it from there.

Sorry for my tedious and confusing description. Do any of you have (or
can suggest) other cheap homeshop chucks or methods for holding a blank
on variable axes with convenient and fairly precise adjustments. If so,
how do those of you bereft of pricey factory chucks do it?

wrote:
Hi Bill

Get the coffee on, here's a few looks and info.

http://homepage3.nifty.com/manasan/e...rning/turn.htm

http://home.vicnet.net.au/~pwguild/o-rosego.htm

http://www.robert-sorby.co.uk/press-...-eccentric.htm

Have fun and take care
Leo Van Der Loo



Thanks Leo ... all I had to do was be reminded of the name "rose engine"
to go looking for this article. Near the bottom you'll find plans and
even a parts kit.

http://www.woodturner.org/products/aw/

Looks like, due to the complexity, work made on such a lathe might well
fetch a serious premium. I'm in. It might take me a while, but I think I
may have found my niche that will get me past a jury.

Bill

--
http://nmwoodworks.com/cube


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Even the Escoulen chucks recomend completely finishing
the area you've just turned before changing the orientation
of the work because you will not be able to return exactly
to any position once you've moved from it. So precise
adjustments aren't part of woodturning.

If you already have a chuck with a couple of sets of jaws
you're pretty much there for changing the axis of rotation.
Chuck up a blank, turn 3/8th to 5/8ths of a sphere on
on end. turn grooves in it if you want to have some index
references. Chuck the ball up and change center line
orientation similar to the expensive ball and socket collet
chucks. Cheap way to try this type of turning. Also
great practice with a skew.

charlie b