Thread: Australian timbers and tool steels

Originally Posted by dubrosa22

I turn hardwoods for instruments (or try to!) and my favourite Aussie wood is Gidgee. Gidgee is rated at a Janka hardness of 4,270 lbf (18,990N). Ranked the 3rd hardest wood in the world.
Gidgee is hard on tools for sure (about the same as African Blackwood which is ranked 7th hardest) but Jarrah which I turn for rough prototypes and practise is much tougher on my carbon steel Marples chisels. Much more wear. Is this the silica effect?

Vaughan

I recall when I turned legs for a chair in Jarrah, the HSS chisel dulled very quickly, and I needed to use a carbide-tipped chisel instead. Those who work Jarrah with handtools are familiar with its ability to dull edges quickly. Some examples more so than others, as some examples are harder or easier to work than others. The characteristics change within samples, so-much-so that I can understand a few who work a single piece not experiencing anything particularly difficult.

And that is what started this thread. The books state that Jarrah is typically low in silica - because it does not grow in silica-infusing conditions? I have had an invitation from a friend in the USA to send him some examples for analysis. I think I will take him up on this.

This has been a wonderful, rich thread, and I thank all the respondents to date.

Regards from Perth

Derek

Jarrah is found only on lateritic soils in south-west Western Australia, in the 650 to 1250 mm rainfall zone. Under optimum conditions it is a tall tree attaining 30 to 40 m in height with diameter at breast heightup to 2 m. On poor sites the species is reduced to a mallee form.Jarrah | Forest Products Commission

Laterite is a soil and rock type rich in iron and aluminium, and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and long-lasting weathering of the underlying parent rock.

Originally Posted by planemaker

Laterite is a soil and rock type rich in iron and aluminium, and is

????

Aluminium is a man made product.

Originally Posted by Picko

????

Aluminium is a man made product.

Think Bauxite.

Bauxite is not a mineral. It is a rock formed from a laterite soil that has been severely leached of silica and other soluble materials in a wet tropical or subtropical climate. It is the primary ore of aluminum.

Originally Posted by Picko

????

Aluminium is a man made product.

Aluminium is an element. It exists at the atomic level and binds readily and frequently with silica in nature. Definitely not man made.

I'm not being condescending, so I hope it doesn't come off that way.

Cheers,
Luke

Aluminum is frequently associated with beer.

Originally Posted by IanW

I think turning & planing are a bit of a different test for a wood, too - the cutting speeds bring in a new variable. I've found that some woods that are an absolute bear to plane will turn quite easily, & I'd put some Gidgee I've used in that category. However, the various 'batches' I've worked with over the last 10 years or so, have been really variable, so its workability very much depends on the particular piece you're dealing with. I imagine you select pretty straight-grained stuff for instruments? I go out of my way to find truly wild stuff for marking-gauge stocks, etc., but usually select straight-grained bits for the beams, not trusting the highly figured stuff to stay straight in a long, thinnish section. The straight-grained stuff is usually not bad at all to plane, rather like Ebony, whereas the wild stuff not only has the crazy grain to contend with, it actually feels harder to cut & seems to dull edges faster.

I realise now this is a handtool forum section! Silly me.

Anyway, as fgar as turning speeds go I haven't yet quite figured out the best results in terms of longevity of tool sharpness. I go far fast as I can except whilst boring.
Indeed, I do work with the straightest grained pieces of wood for my flutes. Saving the figured pieces for end caps, etc. I have turned ringed and straight grained Gidgee and found next to no difference really except that the ringed/figured pieces tend to crack during boring or soon afterwards. Tough, but less stable at thinner dimensions.

Gidgee is great stuff, just expensive and hard to find in good lengths/widths.
The shavings/chips smell like bitter chocolate :P

Good thread

Vaughan

Originally Posted by rob streeper

Aluminum is frequently associated with beer.

Associated with or commonly found in close proximity with?



Regards
Paul

Originally Posted by dubrosa22

The shavings/chips smell like bitter chocolate :P

I'd never thought about it that way, but you're absolutely right.

Originally Posted by Bushmiller

Associated with or commonly found in close proximity with?



Regards
Paul

Doesn't matter to me.

Jarrah is found only on lateritic soils in south-west Western Australia, in the 650 to 1250 mm rainfall zone. Under optimum conditions it is a tall tree attaining 30 to 40 m in height with diameter at breast heightup to 2 m. On poor sites the species is reduced to a mallee form.Jarrah | Forest Products Commission

Thanks Stewie. I posted this information at the start of the thread, with the same link. It was the reason I suggested that the abrasive content of Jarrah were mineral other than silica, and more likely to be those creating an abrasive resin.

Regards from Perth

Derek

I would expect that abrasive aluminium oxides would have a larger effect than silica (silicon oxide) on the sharpness of cutting tools as they are what a lot of sandpaper is made with.

Derek

If I can wear my serious hat for a moment (it's the one that appears brand new) Australian Wood Review has published a number of articles on timber a little more recently than those mentioned in Ian's post (#19), which were more concerned with workability.

Hardness: Issue 59, p84
Density: Issue 74, p76
Toughness: Issue 84, p76

The articles were written by Hugo Ilic, who is a retired scientist who worked at the CSIRO for thirty six years. He has contributed several more articles than those above but these selected would have the greatest bearing on edge degradation and ease of use.

It occurred to me that it may be interesting to contact him, either directly or through AWR to ask his thought on this thread. I have to say that the articles do not delve any further into possible adverse properties of timber other than the contributors to this thread have discussed and he does indeed allude to the silica factor.

The article in issue 59 is particularly pertinent to the discussion here and also includes a table of species identifying hardness and density. Interestingly out of the top ten hardest timbers quoted, seven were from Australia (two were C.America and one Europe) not that I put this forward as being anywhere near definitive.

Regards
Paul

Originally Posted by Luke Maddux

Aluminium is an element. It exists at the atomic level and binds readily and frequently with silica in nature. Definitely not man made.

I'm not being condescending, so I hope it doesn't come off that way.

Cheers,
Luke

I stand corrected. Mind you, the one that Paul drinks his beer from is man made. I prefer mine in glass.