Need help with the cone (middle of bowl)

[Jamie Straw]

Somewhere in passing, I became aware of the technique of leaving a cone in the middle of a bowl while hollowing it out, something about lending stability. Yesterday, I started hollowing out a Madrone bowl, 10" diameter, somewhat less than 3" deep. Decided to use the tailstock, since the tenon was somewhat modest, so a cone developed in the center. This thing's a bear to get rid of. Much of the difficulty may relate to the hardness of this very dry Madrone. In addition, perhaps I went overboard with the cone -- went too deep down the sides of the bowl before starting to wear away the cone? Perhaps a cone in very dry Madrone wasn't such a great idea? What's the best tool technique to wear this thing down?

 

[robo hippy]

I know I talk about it some where in one of my videos..... Can't remember where though.

First, the idea that the cone adds to stability. Tried it several times after hearing about it and just didn't notice anything. I know there are stabilizing bars on the really fancy compound bows and they do operate to reduce some vibration, but once the mass is away from the rim, it will move. It might keep the center more stable since it is attached to it, especially if you have the tailstock attached to the cone, but other than that I just don't see it.

To remove it, use a scraping cut, and you will see many turners do it with scrapers and gouges. If you try the standard push cut, the 'center is spinning so slowly is it actually moving at all' comes into play. A plunge cut, going down through the fibers works better than a push cut into them. With scraper, pretty simple, keep it angled down, and just push gently straight down to the center. I do keep it more on the left side. With a gouge, roll the flutes over to 9 o'clock, and do more of a pull cut from the tip of the cone down into the bowl. If you have a big cone, start on the edge and flare it out as you get to the bottom of the bowl so you have a tapered cone. Nibble the point of the cone down in steps.

robo hippy

 

[Jamie Straw]

I know I talk about it some where in one of my videos..... Can't remember where though.

First, the idea that the cone adds to stability. Tried it several times after hearing about it and just didn't notice anything. I know there are stabilizing bars on the really fancy compound bows and they do operate to reduce some vibration, but once the mass is away from the rim, it will move. It might keep the center more stable since it is attached to it, especially if you have the tailstock attached to the cone, but other than that I just don't see it.

To remove it, use a scraping cut, and you will see many turners do it with scrapers and gouges. If you try the standard push cut, the 'center is spinning so slowly is it actually moving at all' comes into play. A plunge cut, going down through the fibers works better than a push cut into them. With scraper, pretty simple, keep it angled down, and just push gently straight down to the center. I do keep it more on the left side. With a gouge, roll the flutes over to 9 o'clock, and do more of a pull cut from the tip of the cone down into the bowl. If you have a big cone, start on the edge and flare it out as you get to the bottom of the bowl so you have a tapered cone. Nibble the point of the cone down in steps.

robo hippy

Thanks, Reed. Is the scraper to be a round-nose style, perhaps 1" or bigger in size? My 3/4" just got reground to a negative rake scraper, so the only round nose I have is only 1/2" wide. The 1" scraper I have is ground on the left side and tip, but just a little to right of center. Perhaps it would work? I tried something of a pull cut late this afternoon, will try it again tomorrow -- it was one of those fractured afternoons where I never got a chance to settle in the shop, and mentally just wasn't "there" to be in a good place to turn. Curing it all with some red wine and baseball tonight.😎

PS: This bowl is so big and heavy (relatively speaking), I'm being very cautious. It could do some serious damage if it flew off the lathe -- pellet stove glass is in the line of fire.😛

 

[hockenbery]

Somewhere in passing, I became aware of the technique of leaving a cone in the middle of a bowl while hollowing it out, something about lending stability. Yesterday, I started hollowing out a Madrone bowl, 10" diameter, somewhat less than 3" deep. Decided to use the tailstock, since the tenon was somewhat modest, so a cone developed in the center. This thing's a bear to get rid of. Much of the difficulty may relate to the hardness of this very dry Madrone. In addition, perhaps I went overboard with the cone -- went too deep down the sides of the bowl before starting to wear away the cone? Perhaps a cone in very dry Madrone wasn't such a great idea? What's the best tool technique to wear this thing down?

I often use the tailstock when turning natural edge bowls. This provide support for the interrupted hollowing cut.
I also would use the tailstock it I thought I had a compromised tenon.

If you go to minute post 46.28 you will see the cone . I cut a cone left by the tailstock away with a bowl gouge.
NE crotch bowl demo:
http://www.youtube.com/watch?v=8jVoI12Kfug

I cut the cone away with a bowl gouge cutting rim to bottom.
When the cone gets pointy I use one of my favorite cuts
Begin the cut with the tip of the cone inside the flute of the gouge right at the nose.
To start cutting roll the gouge a tiny bit clockwise to engage the lower flute and at the same time pull the nose to the left slightly to get it on center.
When you get it just right the gouge will cut right down through the center. Fun!

With dried wood it works about the same. Maybe smaller cuts.

Have fun
Al

 

[robo hippy]

Jamie, a round nose will work fine. Main use for them I have is for shear scraping because I can go either right or left with them. My go to profile is a 1/4 round, so a bit of the nose pretty much square, then rounding over to the left side. Most common name is 'inside' scraper. The square part on the front is great for plunge cuts like taking out the cone or going down the outside of a bowl blank from the tailstock end rather than from the side. One of the Skew masters uses pretty much the same grind with the straight part being excellent for peeling cuts. The peeling cuts can be done with an angled grind, but then you have to angle the skew on the tool rest rather than having it go straight in.

robo hippy