A bit of practice

[Grumpy John]

I've been practicing turning thin walls lately with various degrees of success. My main problem seems to be bad approach angle resulting in a thin lip as shown on the natural edge silky oak bowl and small goblet. I got the approach better on the cyprus bowl but the damn thing shattered :((. Managed to get some translucence though :2tsup:.

The cyprus was only cut down 8 weeks ago and was sopping wet, fun to turn though. I managed to get a consistent wall thickness before the "mishap" and was happy with the way things were proceeding. I put a few drops of CA on the pieces just to put it back together to show the shape. Looking at the photos I now realise that I probably should have got rid of the pith :doh: and that's probably what caused the blowout.

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The silky was also green but not as wet as the cyprus, still needs some sanding and work done to finish the foot off.

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The goblet bowl is weeping cherry and bone dry. The bottom 2/3rds. is not bad, but the top is terrible due to bad approach angle and lousy sanding techniques, nowhere near thin enough either. It never would have made it to a finished goblet as the centre was rotten and I had no chance of turning a thin stem.

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[Peter36]

Bugger. That would make anyone grumpy. How spectacular was the failure - bits flying all over or do you get a bit of notice of the impending failure so that you can duck/turn off power.

[dai sensei]

All good practice though John :U

With the thin walled stuff I finish from the outer edge and work my way in a bit at a time finishing as I go. Looks like you tried to go back to the outside edge and the flex in the thin wall has caused the failure.

[John Lucas]

You may be pushing on the bevel too hard. That causes the wood to flex or makes it bounce of the summer,winter wood which causes vibration. The vibration will cause the tool to grab the wood and then you get a catch. Try to see how light you can be on the bevel. Try putting more pressure down on the tool rest with your left hand and then be really light with the cut.
another technique I've been playing with is using the bowl gouge with the flute up at 12 oclock. Rotate the tool to about 12:30 so it's not cutting and then very carefull rotate it up until it starts to cut. As you feed the tool down the bowl you may have to rotate the flute more towards 12:30. Just concentrate on keeping that side bevel flat against the bowl.
When I'm cutting with the flute at about 1:30 or 2 I'm pushing the tool more into the wood. This causes the vibration I think because the tool shaft is about 45 degrees or so in orientation to the wood. With the flute up the shaft is closer to parallel to the wood so you aren't pushing against the side as much and you get less vibration and chatter.

[Nai84]

Hey Grumpy John

That cypress bowl that would of been a nice peice to :oo: what a pain in the bum that it shattered on you :( but even put back together it still look awsome :D. The sliky bowl fantastic love it :D well done

Cheers Nai84

[Grumpy John]

Bugger. That would make anyone grumpy. How spectacular was the failure - bits flying all over or do you get a bit of notice of the impending failure so that you can duck/turn off power.

Pretty spekky, bits going everywhere, one piece landed behind the bandsaw. No warning whatsoever, the scary part was that I had my left hand rubbing the outside of the bowl to cut down vibration.

[artme]

Well GJ, at least you have the nerve to have a go!:2tsup::2tsup::2tsup:

I am not yet so brave!:no:

[munruben]

Great effort and a learning curve for you. I haven't tried doing any thin stuff yet. :).

[TTIT]

I've been practicing turning thin walls lately with various degrees of success. ........ I got the approach better on the cyprus bowl but the damn thing shattered :((. ..................................I don't know which cypress you were using GJ but I reckon you couldn't have picked a worse timber for practising thin walls. First one I turned from cypress (native White Cypress (http://www.ttit.id.au/treepages/whitecypress.htm)) sounded like a bowl full of rice bubbles each time I stopped the lathe :;:U

[rsser]

Nice to see you pushing the boundaries GJ

You could also try a small gouge; reduces outward pressure on the rim.