So I've been playing with my new chuck...don't happen to own a dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the way to
the bottom of the
hole I turned, which was the same distance as from the face of the chuck to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance, but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would make sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

--

atv rider polaris 500
glass creations
drz400s
wood carver
spode

http://personalpages.tds.net/~upgeor...ugh%20Page.htm

Read on through. You did it wrong, initially. The way you're doing it now
is correct.

"res055a5" wrote in message
news:_wdFd.6969$u47.6373@trnddc09...
So I've been playing with my new chuck...don't happen to own a dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the way to
the bottom of the
hole I turned, which was the same distance as from the face of the chuck
to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance, but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that
seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would make
sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

Hi Rich

The bottom of your recess or the back edge around your tenon is where
your chuck's JAWS should sit AGAINST, that is what keeps the blank from
wobbling, DO NOT make the recess or tenon to deep/long.
The other problem with the tenon jaws is that you have to have a very
close fit size wise as well as the dovetail's angle has to be close.

You can try this for your self: draw an accurate circle, let's say 3"D
now draw an other accurate circle 1/8" larger or smaller that has one
side against the larger/smaller circle and see how much in contact you
still have ??.

You'll see that you lost at least 50% of the contact surface area, if
you would take 1/4 of that circle as a dovetail jaw, so it is very
important to have a very close fit size wise and also dovetail angle wise.

Now if you keep your tailstock up against your turning at all times
there will be not much of a chance that your piece of wood will come out
of your chuck and it will stay wherever you first centered it, it does
however restrict your access to and manner in which you are able to turn
your project.
Taking this in consideration is why I chose a Oneway chuck with their
standard jaws they do have a superior design IMO.

Have fun and take care
Leo Van Der Loo

res055a5 wrote:
So I've been playing with my new chuck...don't happen to own a dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the way to
the bottom of the
hole I turned, which was the same distance as from the face of the chuck to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance, but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would make sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

the chuck is inside the hole i made for it.
rich
"Keith Young" wrote in message
...
Did you outside or inside mount the wood

apparently I did make the hole wrong...
i made the hole dovetail all the way in...instead of making it straight for
half
the chuck distance and dovetail for the rest...hmm, let's see if i can draw
this:
______ hole ______
/ \
/__________\
should have been this:
________ ______
| |
/_________\
that way the whole jaw contacts the wood and the very end of the jaws
contact
the bottom of the hole....correct?
rich

"Leo Van Der Loo" wrote in message
...
Hi Rich

The bottom of your recess or the back edge around your tenon is where
your chuck's JAWS should sit AGAINST, that is what keeps the blank from
wobbling, DO NOT make the recess or tenon to deep/long.
The other problem with the tenon jaws is that you have to have a very
close fit size wise as well as the dovetail's angle has to be close.

You can try this for your self: draw an accurate circle, let's say 3"D
now draw an other accurate circle 1/8" larger or smaller that has one
side against the larger/smaller circle and see how much in contact you
still have ??.

You'll see that you lost at least 50% of the contact surface area, if
you would take 1/4 of that circle as a dovetail jaw, so it is very
important to have a very close fit size wise and also dovetail angle wise.

Now if you keep your tailstock up against your turning at all times
there will be not much of a chance that your piece of wood will come out
of your chuck and it will stay wherever you first centered it, it does
however restrict your access to and manner in which you are able to turn
your project.
Taking this in consideration is why I chose a Oneway chuck with their
standard jaws they do have a superior design IMO.

Have fun and take care
Leo Van Der Loo

res055a5 wrote:
So I've been playing with my new chuck...don't happen to own a dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the way
to
the bottom of the
hole I turned, which was the same distance as from the face of the chuck
to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance,
but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that
seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would make
sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

res055a5 wrote:
apparently I did make the hole wrong...
i made the hole dovetail all the way in...instead of making it straight for
half the chuck distance and dovetail for the rest...hmm, let's see if i can draw
this:
______ hole ______
/ \
/__________\


should have been this:
________ ______
| |
/_________\

that way the whole jaw contacts the wood and the very end of the jaws
contact the bottom of the hole....correct?

*INCORRECT* !!!!

You need to make the hole just like you did in the first drawing,
only not as deep. You should only make it as deep as it says in the
instructions for that jaw set, which in the case of the standard Nova
50mm jaws is a *maximum* of 6mm, and in any case never deeper than the
flared section of the jaws.

For smallish items you won't need, or want, to make it that deep, and if
I recall correctly they suggest a minimum of 3mm. What you *don't* want
is for any part of the parallel section of the jaws to be inside the recess.

--
Alun Saunders

The jaws should bottom the piece, and the depth should not exceed the depth
of the dovetail portion, just as Alun says. Leo's explanation does not take
this into account. It's not "grip" that counts, it's resistance to force
applied parallel to the axis of rotation. Fortunately, that's also the way
the wood wishes to be cut in a standard bowl mount. The dovetail is a
wedge, not a grip. I thought I included a link to a demonstration
yesterday, but in case you missed it:
http://personalpages.tds.net/~upgeor...ugh%20Page.htm and the
following five pages will show it.

The radius of the recess or the outside of the jaws/shoulder contact
determines the length of the lever perpendicular to the axis of rotation,
and thus resistance to forces applied at right angles to it. I don't know a
practical way of computing it, but I can say from experience that the
decreasing amount of metal in contact with wood parallel to the axis of
rotation caused by larger openings does not seem as significant as the
increase in leverage perpendicular to it in securing a piece. With dry,
less compressible wood, it becomes less important how well the curvature of
the jaws, inside or out, is matched to the wood. You do, however,
sacrifice some recentering assurance if there's a great discrepancy, because
you can easily compress the wood if you apply too much force to the jaws.
Since wood is seldom uniform throughout, the jaws will follow the line of
least resistance, resulting in centering problems _if you "grip" rather than
hold_ the piece. If you apply enough pressure only to maintain contact with
the bottom or shoulder, no problem.

So it's not grip that counts. That's in the wrong direction, and the lever
length is insignificant.

If you're doing end grain work, try to match the circle better, because
hollowing forces are not parallel to the axis of rotation, but more
perpendicular. Best thing to do is get a steady to resist these, but a
large diameter set of jaws is quite a leg up.

"res055a5" wrote in message
news:VCpFd.14484$hc7.1759@trnddc08...
apparently I did make the hole wrong...
i made the hole dovetail all the way in...instead of making it straight
for
half
the chuck distance and dovetail for the rest...hmm, let's see if i can
draw
this:
______ hole ______
/ \
/__________\
should have been this:
________ ______
| |
/_________\
that way the whole jaw contacts the wood and the very end of the jaws
contact
the bottom of the hole....correct?
rich

"Leo Van Der Loo" wrote in message
...
Hi Rich

The bottom of your recess or the back edge around your tenon is where
your chuck's JAWS should sit AGAINST, that is what keeps the blank from
wobbling, DO NOT make the recess or tenon to deep/long.
The other problem with the tenon jaws is that you have to have a very
close fit size wise as well as the dovetail's angle has to be close.

You can try this for your self: draw an accurate circle, let's say 3"D
now draw an other accurate circle 1/8" larger or smaller that has one
side against the larger/smaller circle and see how much in contact you
still have ??.

You'll see that you lost at least 50% of the contact surface area, if
you would take 1/4 of that circle as a dovetail jaw, so it is very
important to have a very close fit size wise and also dovetail angle
wise.

Now if you keep your tailstock up against your turning at all times
there will be not much of a chance that your piece of wood will come out
of your chuck and it will stay wherever you first centered it, it does
however restrict your access to and manner in which you are able to turn
your project.
Taking this in consideration is why I chose a Oneway chuck with their
standard jaws they do have a superior design IMO.

got it !
thanks guys for the advice...it's a little late for the piece i have on the
lathe,
but now i know what to do in the future.

there is a set of 3 jaws on ebay for sale for nova chucks...and i'm
wondering
whether the spigot jaws would be useful for turning goblets?
rich

"res055a5" skrev i melding
news:_wdFd.6969$u47.6373@trnddc09...
So I've been playing with my new chuck...don't happen to own a dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the way to
the bottom of the
hole I turned, which was the same distance as from the face of the chuck
to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance, but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that
seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would make
sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

Can it really be neccessary with all this shaping and tooling?
I use a Oneway talon.
To make the recess I use a Forstner-bit of 2" diameter,
and a depth of 3 - 5mm, depending on the size of the blank.
This gives just a litte clearance when the chuck is compressed.
Then I roughturn the piece, and make a new hole on the opposite side
with a straight parting tool.
After I turn the piece, I clean the first hole with my parting tool,
so as to make sure the two holes are exactly parallell.

I have never lost a piece, except because of faulty wood.

If I had the dovetail jaws, I would still use the exact same method.
I do not see why it should not work equally well.

This scraping business seems somewhat excessive.

Bjarte

"res055a5" wrote in message
news:69zFd.7070$C.3427@trnddc05...
got it !
thanks guys for the advice...it's a little late for the piece i have on
the
lathe,
but now i know what to do in the future.

there is a set of 3 jaws on ebay for sale for nova chucks...and i'm
wondering
whether the spigot jaws would be useful for turning goblets?
rich


That's yes and no.

They certainly offer you a greater grip length parallel to the axis of
rotation to resist the outward forces of hollowing on an end grain piece,
but they are a bear to use to rechuck a piece without losing concentricity,
because they, almost of necessity, distort the wood of the spigot (tenon)
with their serrations. It's almost impossible to get back to the status quo
ante with them if you for some reason dismount the piece, or if turning a
green piece which you leave to dry long enough for it to become oval. Some
people might even get a catch that compresses the wood of the spigot!

I hedge my bets when using them (35mm) by mounting a centering cone (I have
a number premade) on the Nova live center, which offers that opportunity. I
use it to hold things in the proper relationship while trying to reestablish
the contact between the nose of the jaws and the shoulder of the tenon.

I got the power Grip jaws with my Super Nova, and the external dovetail has
done for pieces hanging out 14 inches from the chuck, but you have to start
with a substantial piece of stock to make the dovetail spigot. With the
steady, the 50mm jaws, gripping outside, have proven adequate for the way I
cut.

Nope, you had it right the first time. Almost. You just made the dovetail
recess too deep. Your chuck jaws should bottom out in the recess. The
recess should be a bit shallower than the chuck jaws will reach. The recess
should be dovetailed all the way with no straight-walled portion.

Barry


"res055a5" wrote in message
news:VCpFd.14484$hc7.1759@trnddc08...
apparently I did make the hole wrong...
i made the hole dovetail all the way in...instead of making it straight
for
half
the chuck distance and dovetail for the rest...hmm, let's see if i can
draw
this:
______ hole ______
/ \
/__________\
should have been this:
________ ______
| |
/_________\
that way the whole jaw contacts the wood and the very end of the jaws
contact
the bottom of the hole....correct?
rich

"Leo Van Der Loo" wrote in message
...
Hi Rich

The bottom of your recess or the back edge around your tenon is where
your chuck's JAWS should sit AGAINST, that is what keeps the blank from
wobbling, DO NOT make the recess or tenon to deep/long.
The other problem with the tenon jaws is that you have to have a very
close fit size wise as well as the dovetail's angle has to be close.

You can try this for your self: draw an accurate circle, let's say 3"D
now draw an other accurate circle 1/8" larger or smaller that has one
side against the larger/smaller circle and see how much in contact you
still have ??.

You'll see that you lost at least 50% of the contact surface area, if
you would take 1/4 of that circle as a dovetail jaw, so it is very
important to have a very close fit size wise and also dovetail angle
wise.

Now if you keep your tailstock up against your turning at all times
there will be not much of a chance that your piece of wood will come out
of your chuck and it will stay wherever you first centered it, it does
however restrict your access to and manner in which you are able to turn
your project.
Taking this in consideration is why I chose a Oneway chuck with their
standard jaws they do have a superior design IMO.

Have fun and take care
Leo Van Der Loo

res055a5 wrote:
So I've been playing with my new chuck...don't happen to own a
dovetail
scraper, so I
used a skew chisel to cut the dovetail. Cut it at an angle all the
way
to
the bottom of the
hole I turned, which was the same distance as from the face of the
chuck
to
the end of the chuck.
I noticed that the chuck dovetails for only about half that distance,
but
didn't think that would matter.
It apparently did matter because my piece flew off the chuck a couple
of
times. So I tried mounting it
where the dovetail ended and the straight part started and so far that
seems
to have worked. I have
reservations about whether I should make the hole bigger and turn it
dovetail for half the distance and
straight for the other half. that way the face of the chuck would
make
sure
that my wood was straight.
directions for the chuck seem a little vague (I'm dumb??).
rich

"Keith Young" wrote in message
...
Do you find you get a better grip with an inside mount?
i don't know enough about turning to answer your question...
i'm still a beginner really and it's better to ask one of these other guys
that seem to know.
however, i do like the chuck i bought better than the outside metal turning
chuck
i have attached to a faceplate. it's useful for small things but not when
you need a solid hold
because you will be turning with some force or distance from the chuck. it
has essentially no
gripping surfaces, just compression surfaces. maybe it would work better if
i put CA glue on
the surface to be gripped before mounting it so it would be harder?
rich

It would be nice to see all of this in person, because I get lost in
the forces, axis, perpendiculars, parallels, etc. I have 2 Vicmarcs.
The dovetails on the jaws go all the way down. With the big chuck, and
bowl being 16 inches plus, my mortice is about 1/4 to 5/16 inch deep,
and 1/16 or so wider than the jaws. This allows enough hold to safely
core with the McNarghton system, and no tailstock. On smaller pieces, I
go no less than 1/8 inch deep, depending on size. The top of the jaws
must bottom out on a flat spot in the mortice, and the mortice can't be
deeper that the jaws. Wet wood seems to compress more than dry wood, to
the point that sometimes, I have to retighten the chuck once or twice
while turning. You can tighten the jaws too much, which can break the
mortice before you begin to turn, or if and when you catch, the added
stress, can break your grip. When tightening, there are 2 places on my
chuck to insert the wrench for tightening. I snug it up in one hole,
then go to the next and snug it up some more. I may rotate it a couple
of times, snuging it up a little until I am satisfied. Having enough
shoulder on the mortice is important also. With a little shoulder, you
have to be gentle when turning out the inside, with a bigger shoulder,
you can be more aggresive. Because woods are so different, there are no
fixed rules on how much is enough (shoulder size, mortice depth, jaw
tension). Trial and error will help you learn.
robo hippy

One more after thonght, I use the mortice as my finished bottom. After
using a dovetailed scraper to make the hole, I use a small spindle
gouge for the finish cut. One pass across the bottom and one pass down
the side. The point on the spindle gouge will get all the way into the
corner of the dovetail, which I can't do with a bowl gouge or skew. It
is also easier than sanding it out.
robo hippy


















robo hippy wrote:
It would be nice to see all of this in person, because I get lost in
the forces, axis, perpendiculars, parallels, etc. I have 2 Vicmarcs.
The dovetails on the jaws go all the way down. With the big chuck,
and
bowl being 16 inches plus, my mortice is about 1/4 to 5/16 inch deep,
and 1/16 or so wider than the jaws. This allows enough hold to safely
core with the McNarghton system, and no tailstock. On smaller pieces,
I
go no less than 1/8 inch deep, depending on size. The top of the jaws
must bottom out on a flat spot in the mortice, and the mortice can't
be
deeper that the jaws. Wet wood seems to compress more than dry wood,
to
the point that sometimes, I have to retighten the chuck once or twice
while turning. You can tighten the jaws too much, which can break the
mortice before you begin to turn, or if and when you catch, the added
stress, can break your grip. When tightening, there are 2 places on
my
chuck to insert the wrench for tightening. I snug it up in one hole,
then go to the next and snug it up some more. I may rotate it a
couple
of times, snuging it up a little until I am satisfied. Having enough
shoulder on the mortice is important also. With a little shoulder,
you
have to be gentle when turning out the inside, with a bigger
shoulder,
you can be more aggresive. Because woods are so different, there are
no
fixed rules on how much is enough (shoulder size, mortice depth, jaw
tension). Trial and error will help you learn.
robo hippy