First try at bowl turning, what am I doing wrong ?

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First try at bowl turning, what am I doing wrong ?

Postby llwynog » Sun Aug 17, 2014 9:03 pm

Hello,
I recently completed a bungee/pole lathe and after practicing with a few spindle turned items (grain of wood parallel to the lathe bed), I decided to have a go at bowl turning.
With the grain of the wood now perpendicular, I have very ugly tearout on the end grain. On the picture below, you can see that the top and bottom areas look clean while the area in the middle looks terrible.

Image

What am I doing wrong ? I would be very grateful on any advice for getting a cleaner cut.

I do not have any hooks so I tried with regular (carbon steel) woodturning gouges and skew chisels. The tools are razor sharp but maybe my technique is not good enough ? Would using turning hooks help in getting a smoother surface ? Maybe the gouges' handles are not long enough to give appropriate leverage ?

The wood itself is birch and although it is not completely green, it is still at about 25% of water content. It is also slightly spalted, am I making things too difficult for a first try ?

Looking forward to any comments and advices,


Fabrice
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Re: First try at bowl turning, what am I doing wrong ?

Postby TonyH » Wed Aug 20, 2014 8:44 pm

Since nobody more knowledgeable has replied yet ...

Difficult wood and the wrong tools are your problems IMHO. Birch is not easy in any case, and spalting definitely won't help. Beech and sycamore worked ok for me. And tools - with the wood mounted cross-grain on the lathe, to avood cutting against the grain you need to cut towards the tool rest - hence the hooks. Power lathe turners have speed on their side and can get away with anything !
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Re: First try at bowl turning, what am I doing wrong ?

Postby Brian Williamson » Thu Aug 21, 2014 7:25 am

I'd think that your trouble is mostly to do with the wood. Spalted birch is going to be a difficult wood to get a clean cut from. Try something fresh if you can. Sycamore would probably be the best bet.

Don't be too worried about using gouges rather than hooks. I've done all my bowl turning with gouges and am quite happy with the results. As long as your tools are genuinely sharp (and I always question whether peoples are) you should be alright. Hooks will allow you better access, especially with steeper sided bowls and, of course, if you try and turn nesting bowls. Possibly, in an ideal world, you'd turn the outside of your bowl with a gouge and the inside with a hook?

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Re: First try at bowl turning, what am I doing wrong ?

Postby llwynog » Thu Aug 21, 2014 1:50 pm

Tony, Brian,

Thank you very much for your answers.
I had no idea that birch was a difficult wood to turn: I fell a birch tree in my garden, made a lathe from it and simply used an off-cut as a first try. I discovered that the wood was spalted while axing away the rough bowl.

As you both suggested, the spalting was indeed not helpful to me as a beginner. On close inspection, the tear out occurred mostly in the spalted regions.

I eventually managed to turn a bowl reasonably free of tear out although the shape was more dictated by the recovery of the successive catches/dig-ins than my own will...

ImageImageImage

The things I found helpful in reducing tearout were:
  • Using the smallest possible gouge that I had (8mm) and striving for the lightest cuts as manageable. Anything bigger than this gouge apparently was too aggressive to the frail spalted areas and tore off chunks of wood no matter how sharp the tools. I tried to use the skew chisel but the catches forced me to remove about 4mm in radius each time so I eventually gave up.
  • Sharpening the gouge VERY often. I would typically sharpen the gouge, work for 2 minutes, strop the tool, work for 2 minutes, strop the tool, work for 2 minutes and sharpen the tool afresh. All in all, a pretty time consuming way to work and I probably spent nearly as much time sharpening as turning... I feel that I ended up sharpening more to compensate for my lack of technique. I am left wondering when I read tutorials online mentioning that the hooks need not be razor sharp...

I left the surface as it was cut from the tool and dud not try to sand away the mistakes (merely burnished the surface with wood shavings) as I would like to be able to compare this first bowl to the next ones and see if my technique improves. The 2 last pictures were taken after I coated the bowl with some walnut oil.

Brian, I understand what you mean regarding the difficulty to hollow out the bowl without hooks. I felt that my gouge would only allow me so much angle and I was not able to match exactly the same curve on the inside than on the outside.

Anyway, it was still a nice project, thank you once again for your help.
Last edited by llwynog on Fri Aug 22, 2014 8:02 pm, edited 1 time in total.
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Re: First try at bowl turning, what am I doing wrong ?

Postby Steve Martin » Fri Aug 22, 2014 4:35 am

One question/suggestion for your consideration. When you used the gouge did you push the gouge from the rim into the bowl with the opening of the gouge facing your right hand so you were using the point of the gouge to do the cutting,or did you start at the center with the gouge turned so the opening was towards the wood, facing towards your left hand, and making the bottom edge do the cutting in a very thin slicing action, using a pulling action to move the cutting edge from the center portion to the rim? This sounds a little garbled but if you will try it you may get a smoother cut. The initial shaping cuts can be made with the open face of the gouge toward your right, pushing the edge into the wood. Then as you get to the finishing/final cuts, flip the gouge, so the open face is on your left and pull the gouge from the center to the rim and the "top" cutting edge just missing the wood so the bottom edge is doing a skew cut as you pull it towards the rim. Then when you get your hook tool you can just peel off the slices of wood.
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Re: First try at bowl turning, what am I doing wrong ?

Postby Bob_Fleet » Fri Aug 22, 2014 10:56 am

Simplest advice is to cut 'downhill'.
Imagine the grain of the wood like a telephone directory sitting on a table. If you took a knife and cut across the edge downwards towards the table you'd get a clean cut, however if you tried it upwards the pages would open and the cut would become ragged and torn.
You can usually work out which is downhill on most wood but in bowls you have no choice but to cut across the grain at some stage in the revolution.
Sharp tools make all the difference too.
In general I finish the inside of bowls (power turning) cutting from the rim to the centre so most fibres are cut 'downhill'.
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Re: First try at bowl turning, what am I doing wrong ?

Postby llwynog » Fri Aug 22, 2014 7:59 pm

Bob, Steve,
Thank you for your suggestions. I already started to experiment similar ways of working though I probably did not pursue enough the whole pulling thing.
I'll be sure to give it another try on my next bowl.

Fabrice
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Re: First try at bowl turning, what am I doing wrong ?

Postby Kevin Downing » Wed Sep 03, 2014 5:28 pm

Fabrice,
Attached are photos that might help you visualise cutting downhill. Regards, Kevin
Attachments
core.jpg
core.jpg (116.4 KiB) Viewed 7548 times
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DSC06059.JPG (145.31 KiB) Viewed 7548 times
DSC06058.JPG
DSC06058.JPG (134.31 KiB) Viewed 7548 times
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Re: First try at bowl turning, what am I doing wrong ?

Postby llwynog » Wed Sep 03, 2014 7:26 pm

Thanks for the pictures Kevin !
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