Sunday, 27 November 2011

Lesson Relearned

In my very first turning class I learned three things that have stuck with me ever since:
1: Rub the bevel agaunst the bowl, then slide the tool down the rest while lifting the handle until the tool just starts shaving the wood.
2: Pay attention to where the bevel is pointed, because that is the direction your cut will go.
3: Always cut from the larger diameter to the smaller diameter so the wood fibres are supported by the ones below for a cleaner cut.

The first two were eye opening at the time, but now make total sense.  They are comfirmed with every bowl that I turn and feel very natural.

But I still struggle with the last one.

It just seems to be wrong to me. I think that if you were to cut from the small diameter to the larger one, the fibres higher up stick out further than the one being cut so that the ones being cut are completely supported.  When cutting from a larger diameter to a smaller one, the fibres being cut are always overhanging the the ones further down and hence are not fully suported.  So why am I wrong?

I know that I am because of a little experiment I tried on the inside of the bowl I am working on now.  I was rough hollowing the inside and I was working both from the outside in and from the inside out.  Here is what it looked like when I went from the outside in:

This is what it looked like when I worked from the inside out:

So why the big difference?  Both cuts were made with the same tool in the same wood taking the same depth of cut.  The surface here is fairly flat.  I still just don't get it.

You can't argue with the results though.  I have tried to make some changes to the way I work on bowls to accomodate this, like turning the outside of the bowl between centres with the bottom facing the tailstock and then turning the bowl around and chucking it to do the inside.  Being right handed it is easier to work toward the tailstock because there is more room.  I just don't like taking the bowl off the lathe because it never seems to go back on to the exactly the same centre.  Maybe I just need more practise.  You know, more time in the shop

No comments:

Post a Comment