"Ken Wilson" wrote in message
...

originally i would turn a stepped spigot to fit the lip - but i had one or
two of those fly across the room with the "stepping" bit splitting.
So i took to just doing a straight spigot.

But it tends to slip occasionally.

Two questions then - what does everyone else use - the inside stepped or
the
outside dovetail. If you use the inside stepped do you turn a stepped
spigot or a straight one.

And would a different internal shape be better for bowls such as the
serrated one on the type H Medium gripper or the dovetailed ones on the
Type
A ? (eg the kids don't know what to get me for xmas...)

Oh if it makes any difference - not just bowls of course - I'm still
working on perfecting the ideal eggcup; have had an enjoyable bash or two
at goblets and everybody seems to be getting boxes this xmas.

Couple of red flags showing here Ken. "stepped dovetail" is impossible.
That ridge under the dovetail is the limit of depth, otherwise you lose the
wedge, and start to try to drive a round peg in a round hole, which makes a
split. You have to bottom the jaws in the recess, that's what takes the
strain. Your wedge action helps draw it snug. You're not gripping, which
is why you don't crank on the tension, you just snug the face of the jaws
against the bottom of the mortise. Make sure it's free of dust and chips,
and the bottom is perpendicular to the axis of rotation so it will seat
without wobbling.

Same principle in gripping outside. What really counts is getting the
shoulder you cut perpendicular to the axis of rotation flat up against the
jaws of the chuck. You can use the dovetail, if your jaws have them, to
wedge, but you don't want any part below the limit of the dovetail to steal
the wedge from you by grabbing the wood.

If you use the serrated type for grip, you will have to snug the piece flat
up against the jaws by using your tailstock or some other type of pressure,
because there's no wedging action to draw for you. You might even end up
pushing the piece out of register if you overtighten the jaws, because the
serrations are really bi-directional wedges, and they'll push up and break
through the fibers if you're not careful.

That's why I like the smooth jaws. When you make the tenon or mortise as
close an approximation of the circle formed by the jaws as possible, you
spread the load over a large surface. Means you won't exceed the elastic
limit of the wood when you snug up.

As you saw in the picture I referenced, you can sneak your hold into a
background of decoration pretty easily. The picture is actually of a
mortise which was used initially, and the outside ridges were held as if a
tenon afterward. Neither made a significant dent, and the piece was about
10" in diameter, yet held for hollowing and sanding just fine.

Think fox-wedged dovetails, or the wedge that holds your hammer head in
place.