I am new to turning and have just made my first small bowl (well,
nearly!). I did quite well until I tried to change the flat top (rim)
into a rounded over shape. I wasn't sure how to tackle it so I used a
bowl gouge more or less on its side as I had done successfully for
hollowing the inside, and I approached the inside edge very carefully,
but I got a catch and the bowl came out of the dovetail chuck,
damaging the base. I was able to glue it and try again but the same
thing happened. Can anyone help, please?

Bill wrote: ...snip...."so I used a bowl gouge more or less on its side
as I had done successfully for hollowing the inside, and I approached
the inside edge very carefully, but I got a catch"....snip....
**********************************
Bill,

Without seeing what you're actually doing, it's quite difficult to
correct your approach.
I'm not going to go through a long description of proper tool handling
(I'm sure others will do that better).

Here's what I do when I *think* I'm using a tool right and it goes
wrong: hold the tool as you were but with the lathe OFF. Hand turn
the bowl and watch how the tool edge is reacting. You could have not
turned it at enough of an angle, you want the edge to be more scraping
than cutting as it would when hollowing the inside.

Hope this helps.
Ruth

Woodturners Logo
My shop and Turnings at
http://www.torne-lignum.com

In article ,
says...
I am new to turning and have just made my first small bowl (well,
nearly!). I did quite well until I tried to change the flat top (rim)
into a rounded over shape. I wasn't sure how to tackle it so I used a
bowl gouge more or less on its side as I had done successfully for
hollowing the inside, and I approached the inside edge very carefully,
but I got a catch and the bowl came out of the dovetail chuck,
damaging the base. I was able to glue it and try again but the same
thing happened. Can anyone help, please?

Bill:

The time to get the right shape on the rim is early in the process, not
after the bowl has been hollowed -- especially if it is thin. The rim
will change shape and when you go back to it -- well, you know the
result.

Generally, work from top to bottom and try not to go back up when
working on the inside of a bowl.

Also, why do you want the rim rounded? A rounded and sanded-over rim is
the mark of a machine-made production bowl. I'd suggest you give the
rim some character -- it should have two edges (not sharp, though) and
slant either inward or outward -- not straight across. It can be
slightly rounded rather than flat. That way it looks to be a well-
thought-out design element.

Bill

Bill,

Ruth's advice is good. It is an easy way to diagnose what is happening.

If you were scraping the rim, then I doubt if you would get a giant catch.
If scraping, do it lightly.

If you were cutting across the rim, which I suspect, the dynamics of a catch
are very subtle. To explain what might have happened, try this experiment.
With the lathe OFF, hold a skew point straight into the rim (just touching)
with the handle parallel with the spindle's axis. Orient the cutting edge
vertically, with the long point down. Now raise the handle slightly so that
more of the skew's cutting edge contacts the bowl rim. Now, turn the bowl
by hand. The sharp edge of the skew will make a line all the way around the
rim if it is EXACTLY vertical. If it is even the tiniest bit tipped toward
you, the skew edge will spiral out. If it is tipped away from you, the skew
will spiral in.

When starting a gouge on a spinning surface, the gouge's cutting edge acts
exactly like this until the bevel is rubbing. When the tool is laying on
its side with the flute pointed to the left or right, there is a tiny piece
of the cutting edge that is vertical and will track correctly around the
bowl's rim. Even the slightly misalignment forward or backward will cause
the tool to rapidly spiral in or out and possibly cause a catch. The trick
here is to be firm with the tool when introducing it into the rim. For that
brief amount of time that there is no bevel rubbing, the only support the
tool has is your hand on the tool rest. Make the flute dead flat as you
can, then be firm on the start of the cut. Assuming that you are cutting
away from yourself, if the tool is tipped back a bit, the tool will tend to
kick away safely from the work. If the tool is tipped away from you, the
tool will tend to dig into the work and cause a catch. As you learn where
that exact spot is, err on the side of a kick out rather than a dig in.
Then you can make tiny adjustments on your hand positions until you hit it
just right.

Hard to explain without showing you, but I hope it makes sense.

Joe Fleming - San Diego
==============================




"Ruth" wrote in message
...

Bill wrote: ...snip...."so I used a bowl gouge more or less on its side
as I had done successfully for hollowing the inside, and I approached
the inside edge very carefully, but I got a catch"....snip....
**********************************
Bill,

Without seeing what you're actually doing, it's quite difficult to
correct your approach.
I'm not going to go through a long description of proper tool handling
(I'm sure others will do that better).

Here's what I do when I *think* I'm using a tool right and it goes
wrong: hold the tool as you were but with the lathe OFF. Hand turn
the bowl and watch how the tool edge is reacting. You could have not
turned it at enough of an angle, you want the edge to be more scraping
than cutting as it would when hollowing the inside.

Hope this helps.
Ruth

Woodturners Logo
My shop and Turnings at
http://www.torne-lignum.com

I used to have the exact same thing happen to me except my bowls usually
exploded. Like Bill Rubenstein suggests, do your rim shaping early on in
your hollowing process before you start hollowing below the rim very much at
all. That's made the most difference in my bowl rims. And, as others have
already mentioned, a light scraping action works quite well here.

- Andrew



"Bill" wrote in message
om...
I am new to turning and have just made my first small bowl (well,
nearly!). I did quite well until I tried to change the flat top (rim)
into a rounded over shape. I wasn't sure how to tackle it so I used a
bowl gouge more or less on its side as I had done successfully for
hollowing the inside, and I approached the inside edge very carefully,
but I got a catch and the bowl came out of the dovetail chuck,
damaging the base. I was able to glue it and try again but the same
thing happened. Can anyone help, please?

The real answer already given - make edge detail early early while the bowl
is still close to circular - I'll explain a bit of why the bowl blows up or
runs off. As you look at a wooden bowl cut "normally" with the heart
toward the bottom, it's not circular, but oval. The longer grain portions
are less distance apart then the short grain. Nothing wrong with this,
except it's the worst condition to have to try and work the rim. Your tool,
unless carefully presented, will be going from a void into the uphill side
of the long grain. This is a recipe for a catch or, at the least, an ugly
spot of torn grain even when inside the bowl, so it's best to avoid having
to do this on thin rims which might shatter.

But, if you are working the rim, start your cut into the face, not the
slope, where your tool will have full support as it makes entry, and the
difference in diameter will become merely a difference in shaving width,
rather than an uphill tear, squirm and dismount. It also makes sense to
make it a cut at minimum radial pressure, to avoid distorting what you have
further, and possibly breaking it. I use the same entry cut when doing the
semi final cuts even below the rim, as it allows the gouge to sever the
fibers under inward compression rather than ripping them and creating
sanding problems.

If I were going to scrape, it'd have to be a _really_ light contact on a
_very_ narrow area, and I'd still start in full contact at the face and roll
to the inside.

"AHilton" wrote in message
...
I used to have the exact same thing happen to me except my bowls usually
exploded. Like Bill Rubenstein suggests, do your rim shaping early on in
your hollowing process before you start hollowing below the rim very much
at
all. That's made the most difference in my bowl rims. And, as others
have
already mentioned, a light scraping action works quite well here.

Many thanks to everyone who responded to my question, especially Ruth,
I particularly like her idea of turning the work by hand to see what's
happening at the tool (and I like her web site).
I managed to sort the problem by using a scraper but it's quite
worrying how quickly a catch can happen. I did the inside of the bowl
easily (much to my surprise!) but just coming on to the rim nearly
wrecked it.
Thanks again
Bill