that's some good info mark, thanks.
save your lignum blank as that is relatively easy to turn in comparison to the timbers i'm thinking of.
the really hard to turn african, australian and south american timbers from these areas can yield some tricky customers and i could provide you with some of you like so you could see what i mean?
i could send you some greenheart, angelim vermelho, ekki or ipe if you like.
Thanks for your reply. Yes I have turned such woods one point I highlighted previously in relation to turning the Ozzie wood with the M42 while in Oz, and the Crown M42 Razor edge have a further cryogenic treatment so I know how they will cope with hard woods.
The place for testing is in the metallurgy lab which has been done, the reason for this is that there are scientifically proven methods of testing hardness/Rockwell and tensile testing and then the balance between each depending upon application.
It is kind of you to offer these woods, but as I say I have turned some of them and know the outcome and indeed had a piece of green heart brought to me a while ago. I however choose to only turn very few exotics as I see no point in raping the world of exotic woods that come from countries where there have been proven cases of corruption and vast sums of money changing hands to get the appropriate paperwork signed off to show it is from a sustainable source when it is not.
Also my preference is not to turn woods that have been transported on vast journeys on fuel guzzling and CO2 spewing vehicles and ships just to satisfy my need to turn something when we have so many amazing home grown timbers that I can obtain 20 minutes from away.
Most exotic timbers are horribly noisy, dusty and toxic when turned, in fact I would go as far to say vile so I make the choice not to.
I am sure that you understand about Hardness and tensile testing, I have to say I remember the basics from my apprenticeship days but that is a distant memory so I have included some PDF links below for you to get into.
http://civil.eng.buffalo.edu/CIE616/2-LECTURES/Lecture%204a%20-%20Material%20Testing/HARDNESS%20TEST.pdfhttp://www.asminternational.org/documents/10192/3465262/05105G_Chapter_1.pdf/e13396e8-a327-490a-a414-9bd1d2bc2bb8The effects of Cryogenic treatment on M42 HSS below and a direct quote (source kivak PDF, page 2 chapter 1)
y. In the literature, results showed
tool-life improvements ranging from 92 % to 817 % for
the cryogenically treated HSS tools in the industrial
use.13http://mit.imt.si/Revija/izvodi/mit156/kivak.pdfThere is not a need for me to send any more tools out for testing as this has been done, also the science produced by scientists and metallurgist are proven.
I will attempt to get the Rockwell figures if I get time today the tools, however a higher figure does not necessarily mean a longer edge retention as it is a combination of hardness, tensile and other properties. As explained in some depth within the PDF below
http://www.isibang.ac.in/~library/onlinerz/resources/Enghandbook.pdfThe benefits of Cryogenic treatment over just surface hardening is that it changes the molecular structure through the entire metal as clarified on the front page of the web site below.
http://www.metlabheattreat.com/cryogenic-treatment.htmlAs it can be seen there is quite a bit of science that goes into the producing of various metals and Crown Tools are not in the business I would say of not knowing their trade. For this reason and the in depth knowledge require to produce such tools I simply ask the question of the experts ' what are the benefits' ? ' they are sharper edge and longer wear resistance' that is all I need to know and in use they are markedly better.