Snagging, catching, jumping and banging...

[Lee J]

...all words I would use to describe my first attempt at turning a bowl. I have done some turning before but nothing that involved some internal turning (IE: hollowing out!). So I set about this bowl using a nice piece of zebrano I bought a few years ago.

I had the lathe speed set to 2000 rpm and I was using a bowl gauge.
I turned the outside and bottom without incident but when I was turning the inside walls the chisel seemed to keep catching almost snatching it out of my hand at times. I had the rest set up just below the centre so when my chisel was in contact with the wood it was just above centre. I had the chisel sort of on it's side (the flute to the right) and I started ok. Nice shavings coming off. Then I decided I wanted to make the walls a bit thinner and every time I went down the inside wall it snagged. Sometimes half way down and sometimes when it got to the bottom. I managed to finished the piece off but it took ages.
I followed to the letter a youtube video of a very experienced turner making a simple bowl. He seemed to do it effortlessly.

Is this to do with a non sharp chisel? I struggle to sharpen chisels as I have no jig or system. Would a sharpened chisel help matters?

your help would be good. In the meantime heres my first bowl...

 

[Tazmaniandevil]

Sharp tools are a must for a decent finish. The grind of the gouge makes a huge difference though. Have a look at Cap'n Eddie on youtube for setting up jigs to help with grinding. There are plenty of plans out there too for making grinding jigs.

 

[nev]

Sounds like the tool was not riding on the bevel and therefore had no support leading to catches etc. see a brief explanation here (about 6 mins in) or here or here
Also if you have a bowl interior with sides and a bottom (like your pic) as opposed to a single flowing curve you will find it nigh on impossible to cut that in one. You will ( I do at least) need to shape the side and the bottom separately then gently blend them together possibly with a round scraper.
HTH

 

[Noggsy]

As well as the above, you are likely to need two bowl gouges for flatter shaped bowls. I use a long-grind bowl gouge for the outside and some of the inside of bowls, but the walls of your bowl will sometimes (depending on angle) get in the way of the shaft of your tool, causing the bevel to lift and reducing your control. I find a flatter ground (i.e. with a less acute angle between the shaft and the bevel) gouge very useful in avoiding catches at the bottom of bowls.

 

[jumps]

It would be helpful to see a picture of your rest and tool position relative to the side of the bowl, and a second image close up of the tool tip as presented.

Without these it's only really possible to discuss generalities (such as sharp tools) but as you seem to know what you are doing I'm not sure they will help a lot.

As Nev suggests, the symptoms are consistent with an unsupported cutting edge - and from your description it's starting supported but something in the geometery is changing as you make the cut.

 

[paulm]

Where are you based Lee ?

Would be worthwhile spending some time with a more experienced turner if you can, if any are close by, as much easier to help when you can see what is going on. Having said that it does sound likely to be the unsupported bevel as you turn into the base as already mentioned.

Cheers, Paul

 

[Paul Hannaby]

First, your speed is too high - as a rough guide, divide the diameter of the bowl in to 6000 so for a 6 inch bowl it would be 1000 rpm.
Second, Zerbrano is quite a hard, unforgiving wood so not the best to practice with.
Third, your internal bowl shape is making things difficult for you where the change in direction is. A standard bowl gouge will almost certainly lose bevel contact at that corner. Go for a simple curve and you will find it much easier.
Fourth - yes, sharp tools are an absolute must! You don't need a jig to sharpen a bowl gouge unless you use a fingernail grind. I grind mine straight (but angled back), which I think actually makes things easier for hollowing.

You might find this useful for bowl turning http://www.hannaby.com/start-bowl-turning.html

 

[nev]

First, your speed is too high - as a rough guide, divide the diameter of the bowl in to 6000 so for a 6 inch bowl it would be 1000 rpm.

Great tip and at 3.40 in the morning :shock:

 

[CHJ]

First, your speed is too high - as a rough guide, divide the diameter of the bowl in to 6000 so for a 6 inch bowl it would be 1000 rpm.

Great tip and at 3.40 in the morning :shock:

If you don't want to work the old brain too much if you work in Millimeters not inches there is a list of suggested speeds here.

 

[gregmcateer]

Great tip and at 3.40 in the morning :shock:

Impressive! (I know why he was awake then :wink: ) - AND he was still awake all the way through today when he showed me both his bowl savers AND gave me some excellent tuition on sharpening and spindle work - Marvellous!

Lee - If you are based anywhere nearish to Gloucester, give Paul a yell and get over there for a lesson - You won't regret it for a moment.

Greg

 

[Tazmaniandevil]

One of these days I hope to be able to sharpen consistently without a jig, but at this early stage I need to get the best edge possible. One of the things I will do at some point is get professional tuition including sharpening.

 

[woodturnerEric]

Personally,I wouldn`t go above 600 revs hollowing out the inside of a bowl,also if the tool is getting blunt you can normally tell,as you have to start pushing harder on it to make it cut,or it starts bouncing over the grain,if you don`t have any jigs,then a good deal of patience is called for to keep the angle the same,but with practice it gets easier.When the tol keeps catching,it can be a sign that the bevel isn`t rubbing,or the tool is being held at the wrong angle,ie cutting with the wrong wing of the gauge,regards,

Eric.

 

[Lee J]

Right, I've spoken in person with an expert turner, a chap who actually puts his work into shows and sells loads. Really good stuff. He's offered me free tuition in his workshop for both sharpening and turning. He knew straight away what I was doing wrong. Combination of incorrect stance, not sharp enough tools and working against the grain. He said not to worry, he'll get rid of the bad habits and have me turning properly in no time at all.

I think I'll take his kind offer.

 

[jumps]

Right, I've spoken in person with an expert turner, a chap who actually puts his work into shows and sells loads. Really good stuff. He's offered me free tuition in his workshop for both sharpening and turning. He knew straight away what I was doing wrong. Combination of incorrect stance, not sharp enough tools and working against the grain. He said not to worry, he'll get rid of the bad habits and have me turning properly in no time at all.

I think I'll take his kind offer.

beware - bowls can be addictive...... 8)

this is definitely the best way to go about taking an issue like this forwards, in the abscence of a club environment. it can bring together competence and confidence in a way that articles, videos and DVDs can't.

 

[henton49er]

There is no substitute for some expert tuition.

I thought I was doing quite well after just over a year or so of turning. A day's tuition with Les Thorne in Alresford showed me that there was much to learn and plenty of room for improvement. My tool control and bowl/platter turning has improved significantly with what Les showed me and lots of subsequent practice.

 

[andersonec]

There's a good German video here which may help.

http://www.youtube.com/watch?v=g7-t1dOq ... re=related

It is an extract from a teaching video which has some close ups of hollowing etc.

The natural edge bowl is Robinia and the liquid in the bucket is Ammonia, it was left in the bucket for one hour.

Andy