Newbie question: Turning ash bowl

[Maccy]

I was trying to turn an ash bowl for the first time wgen it went fairly wrong as the picture shows. I let the wall get far too thin then there was a small catch when shaping the lip resultong on this lovely asymetric offering.

However my question is:

How good a cut finish should i expect from this wood.  Just below the broken section the end grain cut looks rather rough is this just normal tearout or the best i can expect?

[fuzzyturns]

This is all a question of practice and technique. It's almost impossible to avoid end grain tear-out completely when turning a bowl. There are always 2 points along the circumference where your tool is running directly into the grain, and these are always the tricky spots. What you can do to avoid this as much as possible:

• Correct technique helps a lot. This is hard to explain, and best achieved with some tuition (and then lots of practice). In essence the trick is to present the tool in such a manner that the cutting part of the edge goes across the surface at a 45 degree angle.
• Keep your tools sharp. Dull tools cannot cut, they can only rip (or scrape), causing far more damage than good. In addition, dull tools require force, which further adds to the damage.
• Higher speed often results in a better cut, simply because the tool does not have to remove so much wood on each revolution. However, higher speed also requires good tool control and confidence. Again, experience will come.
• Cut with the grain, or "downhill". On a bowl (with the grain running perpendicular to the ways of the lathe) this basically means on the outside of the bowl cut from the centre towards the rim, and on the inside cut from the rim to the centre. When you cut against the grain, the fibres you are cutting are not supported by the bevel and will try and avoid to be cut, thereby causing tear-out.

And yes, for a newbie this is far too thin. I know a lot of quite experienced turners who would shake in their boots if you asked them to turn a bowl this thin. Plus, there is no point to it, paper thin bowls are essentially useless.

[Les Symonds]

I'll add one more thing to Fuzzy's comments (all of which, I concur with).
You say that....

...I let the wall get far too thin then there was a small catch when shaping the lip...

....that's a part of the problem. Get the lip/rim sorted as early as possible in the hollowing process and then work down into the body of the bowl. Returning to the lip/rim after creating any thickness of wall is asking for trouble, because the bowl will flex a little under the pressure of the gouge. You can sometimes get away with that if you really know what you're doing, but in the majority of cases you'd get vibration and chatter marks on the timber at the very least, possibly worse!

Les

[The Bowler Hatted Turner]

I agree with the comments made, perhaps you would be better off concentrating on turning bowls with even wall thicknesses before trying to push the envelope and making thin stuff.

[Maccy]

Thanks for all your comments, i hadnt thought about the issues returning to the lip and it then being unsupported.

I was aiming for about 8mm thickness but got carried away at the turn. Ill know for next time.

Ive got a session with a local woodturner coming up so hopefully this will help stop some of the basic errors.

[The Bowler Hatted Turner]

Maccy you can always stop the lathe and take measurements, as you get more experienced you will be able to use your fingers as verniers with the machine still running. But walk before you try to run.

[burywoodturners]

It is good to see that you have found a local turner to help you, I suggest that you look at the list of clubbs on the AWGB website and see if there is one near you, there you will find a wealth of advice.
Ron

[Bryan Milham]

Maccy,

Firstly don't worry about what happened, I think it's fair to say we've all turned lampshades (gone through the bottom of a bowl), and when learning it's all too easy to let the tool take over and what seems like a good, smooth running cut is not actually going where you want it to go. Time and experience will sort both those out.

For the undercut you were attempting.

When doing demo's at clubs, I sometimes pull out a bundle of barbecue (thin bamboo) skewers and use them to simulate the grain of the wood to show how the tool cut needs to be supported. saying 'Cut downhill', 'into the wood' etc., is not always the correct explanation.

If you have some skewers or drinking straws, hold them in a bundle and chop a 'U' shape into one end with the fingers of your other hand. Now look at the ends of the straws, if you are cutting from the rim, inwards, you are cutting over unsupported grain. You need to scoop out the bulk and then cut from the bottom of the undercut, up to the widest part of the timber to get a supported, smooth cut. It sounds counter-intuitive, but it does work.

[bodrighywood]

Maccy,

Firstly don't worry about what happened, I think it's fair to say we've all turned lampshades (gone through the bottom of a bowl),

design opportunity you have now made a tazaa

When doing demo's at clubs, I sometimes pull out a bundle of barbecue (thin bamboo) skewers and use them to simulate the grain of the wood to show how the tool cut needs to be supported. saying 'Cut downhill', 'into the wood' etc., is not always the correct explanation.

talked about this to students but not thought of it as a demonstration visually. Pinch this idea please?

Pete

[Bryan Milham]

talked about this to students but not thought of it as a demonstration visually. Pinch this idea please?

Pete
[/quote]

Pete, feel free

[The Bowler Hatted Turner]

Bryan that is a good visual aid, I usually use a book to simulate the same thing but your idea has given me an idea which I may well develop into a training aid too.
Every day is a school day!!

[Nick Simpson]

Sorry - not got this quote thing working
But these statements seem contradictory

1.  Cut with the grain, or "downhill". On a bowl (with the grain running perpendicular to the ways of the lathe) this basically means …………………………………….. on the inside cut from the rim to the centre.

2.  You need to scoop out the bulk and then cut from the bottom of the undercut, up to the widest part of the timber to get a supported, smooth cut. It sounds counter-intuitive, but it does work.

I completely agree with both of these but
In my limited practice compared to you guys these are two quite different 'cuts'. For the former I would use a push cut using a gouge with a short bevel and for the latter a pull or shear cut with a gouge with a longer grind and again a short bevel.

Am I right to be confused?

Thanks
Nick

[fuzzyturns]

Yes, this is a little confusing. The problem essentially is that at the widest point of the undercut the direction of the cut should change (in theory). If you were to slice the top of the bowl off precisely at the widest point you essentially end up with a normal bowl (where you cut from the rim towards the centre) and a ring (where you should cut from the rim towards the centre). The "rim" in both cases being the widest part of the previous undercut.
Now, the real problem is that because this is an undercut, you will have a really hard time cutting from the "rim" to the edge of the undercut, simply because you can't fit a tool in there, other than maybe a round nose scraper. And depending on the steepness of the undercut, you not even be able to follow this curve coming from the other side.
So, in summary, undercuts are tricky. And that leads me to say: as a beginner, don't try this at home, get some good experience with "normal" bowls first, and a good understanding of why certain cuts work (and others don't) and then revisit the whole thing.

[John Plater]

Hello Newbie,
Plenty of good advice here and much wisdom based on accepted practice but don't be put off from trying things out for yourself. That way the advice offered can be placed in context. You may learn what advice to accept that works for you. If you are enjoying your woodturning in safety what does it matter ? Mistakes will happen whether it is a beginners' piece or a professionals' piece. We are only human and wood is what it is. There are probably as many "right ways" as there are woodturners and all will have a view on that, myself included. It takes a certain patience and doggedness to learn from mistakes made but it might be more meaningful to have at least tried.
Well done for trying !
ATB John

[The Bowler Hatted Turner]

Newbie I turn for a living and have done for many years, I still have failures, some more dramatic than others but failures none the less. Sometimes dissapointment comes with the wood.