General Category > General Discussion
Newbie best way to get rid Of end grain tear Out after Turning A bowl
thebowlerhattedturner:
Hello Bill,
on re-reading my comments earlier on this post I realised my fingers were typing quicker than my brain was thinking, I wrote:-
I think your problem is you are rubbing the bevel during the cut,you may have your tool ground at the wrong angle to achieve this on this design of bowl. Bevel rubbing is very important.
It should read:- I think your problem is you are not rubbing the bevel during the cut etc .etc.
Regards
John
arcos:
My 'speed table' is in my head... It's called fear! :-[
I have started turning at higher speeds as my confidence has grown BUT still keep to mid range speeds (my comfort zone) even when I know that I could run little higher speed.
I have an issue with some wood that is very 'seasoned' and has started rot in places. It turns really nicely and is solid enough but the end grain even with sharp tools, light cuts still results in tear out.
I turned two bowls and had the exact same problem on both. I have yet to experiment in ways to try and stabilise or harden the end grain prior to taking final cuts but there are some interesting ideas on this thread, thanks!
Mark Sanger:
I have put a link in the Web site, videos section, but here is one from the same site that may be of use and goes through the problems.
http://www.woodturningvideosplus.com/torn-grain.html
woodndesign:
As with Andy's reply, I'd like to thank both Marks and Nick as well for their valid knowledge and for their time to post on what is a grey area of speed (lathe that is) for some this is the only place of contact, for others it can be passed onto them by someome, I learnt this or I do such, then it could just be from a book, for some we have set 3, 4, 5, upto 10 speed ranges, with VS what 0-3000 upto 4000+ rpm on some.
Yes given a piece maybe 6" dia or any other dia. to that regard, doesn't take into acount the piece could be anything from 2" to 6"+ in thickness, we can find, read and hear all kinds of formulae and tables, but it is what your safe and comfortable with that is important at all times.
My question with Bill was what speed he used, was more as a consideration to the many factors involed, just as it is that he was using Elm, so is speed relevant to tear out, I'd not considered it to be as such.
And Bill your important to us all, where are you, keep posting.
Cheers David
Mark Sanger:
David
yes speed can be directly related to tear out depending upon the wood/chip formation of the species, how dry it is, interlocking grain etc etc.
All materials have a speed by which they like to be cut. So on top of tool presentation and sharpness as already mentioned then feed of the tool and speed can also be an issue.
Even with the sharpest of tools and correct presentation if traversing the tool is too rapid for the wood beyond the point of efficient chip formation then the fibres can tear out.
So it comes down to geometry, sharpness, speed and feed, this is in turn dependant on wood species and the respective chip formation which in turn can alter the geometry of the tool use.
IE a soft wood cuts easily with an acute angle whereas a very dense timber or alternative material will chip better with an obtuse angle and at time negative rake.
Even the shape of a bowl can make a difference to finish with some woods.
This is why the charts as mentioned are of little real purpose.
The point I am hoping to get across is there is no simple answer :) and while yes forums are useful there are many in depth answers and solutions that only a book, DVD or tuition with in depth explanations and practical application can answer.
Often (certainly with me) these books have to be read/ referred back to more than once for it to sink in, such explanations are difficult and lengthy to clarify in a forum and often answers only confuse, are not presented in a concise clear way/especially without diagrams to be of use, and end up being another hurdle ( although they are posted with good intention and much knowledge) some things have to be shown.
So in short yes speed can have an effect on tear out if it is considered along with with feed rate, material/wood species, tool geometry for the material/species etc.
There is a very good book that ( yes I know it is a book) :) that goes into this in much depth and after reading it several times made me realise that we have to fully understand the substrate we are cutting (wood) to know how to present tools/cut it etc.
http://www.amazon.co.uk/Understanding-Wood-Craftsmans-Guide-Technology/dp/1561583588/ref=sr_1_1?s=books&ie=UTF8&qid=1366991150&sr=1-1&keywords=understanding+wood+technology
it was one of the best investments I ever made. In fact I would say probably the best investment in my development as a woodturner as once we really understand about wood then we can start to understand how to get the best out of it with our tools. Without this knowledge it is like trying to bake a cake in the dark without a recipe. :)
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