Thread: Australian timbers and tool steels

Hi Derek

How do you want to answer this?

One approach would be to go through the Wood Database and extract the density, Janka hardness, etc for as many woods as desired, along with data from the qualitative fields dealing with workability, finishing, nail holding and attempt to establish some correlations.

Another approach would be to go through old issues of Australian Wood Review -- dating back to around 1995 -- where workability and edge retention was discussed, explored in the context of plane blades (in particular Paul William's M2 blades).

otherwise you might just be looking at opinions.

Can't say I have had a lot of experience with fine tool steel edge woodworking but I can comment on Silica content.

Silica content seems to be dependent on climate stress. This is quite noticeable when milling a yard tree versus a tree that has been in an area of bush where it has not seen much water especially in the last few decades around Perth. Tuart seems to be the most common trees that have this problem. Some deposit enough silica so that occasional sparks can be seen when cutting a clean dry wood on a long dead tree i.e. tree has probably died from lack of water. This is also supposed to happen but to a lesser extent in Jarrah and Marri.

In general timber hardness still dominates chainsawing because it's as much a puncture and tearing action akin to chiselling as it is cutting. The first time I milled an ironbark I could not believe how much extra it demanded of the chainsaw. If ironbark had been the first species I had milled I would have given up and gone home. About the 3rd log I milled was some sort of rock hard desert gum and it was bone dry and I managed to blow up the 50cc 40 year old well used chainsaw I was using at the time. I was not that fussed because that saw owed me nothing and I treated it as a learning exercise.

Another species that has given me grief is Rock Oak, a type of hard sheoak that grows in the WA wheatbelt. This also pulls up a lot of silica and I won't mill these unless they promise to yield a decent bit of timber.

Hi Ian

I've looked at Janka hardness. Is hardness enough to explain wear? Other than hardness (where Aussie timbers are clearly well above the rest of the world), what else causes wear in our species? I assume that different timbers growing in different parts of the country will bring with them their own special attributes.

For example, The Wood Database describes Jarrah ...

Workability: Jarrah tends to be difficult to machine on account of its high density and interlocked grain. Jarrah also has a moderate blunting effect on cutting edges. Jarrah turns, glues, and finishes well.

The Forest Product Commission reports ..

Jarrah is found only on lateritic soils in south-west Western Australia

Wikipedia notes, 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.

This says to me that the dulling is not from silica but from iron and aluminium. Yes, no?

Regards from Perth

Derek

Hi Bob

Thanks. Although anecdotal, your comments support the impact that hardness has on wear. Do you, and others, know of articles/references which look at this? Is hardness sufficient to explain wear (noting that other aspects will compound the abrasiveness of wood, such as silica)?

Regards from Perth

Derek

Originally Posted by derekcohen

Hi Ian

I've looked at Janka hardness. Is hardness enough to explain wear? Other than hardness (where Aussie timbers are clearly well above the rest of the world), what else causes wear in our species? I assume that different timbers growing in different parts of the country will bring with them their own special attributes.

For example, The Wood Database describes Jarrah ...

Workability: Jarrah tends to be difficult to machine on account of its high density and interlocked grain. Jarrah also has a moderate blunting effect on cutting edges. Jarrah turns, glues, and finishes well.

The Forest Product Commission reports ..

Jarrah is found only on lateritic soils in south-west Western Australia

Wikipedia notes, 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.

This says to me that the dulling is not from silica but from iron and aluminium. Yes, no?

Regards from Perth

Derek

In part this is what I was alluding to -- to do this properly you need a lot of data points

eg
Jarrah (Eucalyptus marginata) -- Hard or Rock Maple(Acer saccharum) -- Black Cherry, American Cherry (Prunus serotina)
Denisity (dried) -- 835 kg/m³ -- 705 kg/m³ -- 560 kg/m³
Janka Hardness -- 8,270 N -- 6,450 N -- 4,230 N
Modulus of rupture -- 108.0 MPa -- 109.0 MPa -- 84.8 MPa
Elastic Modulus -- 14.70 GPa -- 12.62 GPa -- 10.30 GPa
Crushing strength -- 66.2 MPa -- 54.0 MPa -- 49.0 MPa

Workability -- Jarrah tends to be difficult to machine on account of its high density and interlocked grain. Jarrah also has a moderate blunting effect on cutting edges. -- Fairly easy to work with both hand and machine tools, though slightly more difficult than Soft Maple due to Hard Maple’s higher density. Maple has a tendency to burn when being machined with high-speed cutters such as in a router. -- Cherry is known as being one of the best all-around woods for workability. It is stable, straight-grained, and machines well.


So, just on those three species which I know you have worked with in the past, Crushing strength might be as important as Janka Hardness when it comes to workability. Then it might be a function of how straight the grain is.


as I alluded to, it's potentially a big task.

Hard timbers generate more heat at the edge. Heat is bad.

Kuffy, the heat (through friction) element is possibly a factor, although I don't know if this really offers enough explanation.

Ian, thanks again. I tried to find any Australian Wood Review articles without luck. On a Google search I came up with a gem of an article, AUSTRALIAN EUCALYPTUS TIMBERS, which has a chapter on "The Chemical Products of Australian Eucalypts". Editing this to the salient factors, the introduction starts,

1. General. - The important Australian genus, Eucalyptus, is remarkable for the number and diversity of its chemical constituents. It might perhaps appear from a cursory glance that these were distributed throughout the several groups in an irregular manner, but research has shown that this is not so, for a most orderly arrangement is traceable through the various members and groups of the genus, a peculiarity which suggests a predominating influence of evolutionary conditions.

The article then goes on to discussing a number of influences:

Inorganic factors: Understandably, different regions in Oz will influence differently, however "A striking peculiarity in the eucalypts is the relative constancy of the element manganese in the ash of related species." ...."In some eucalypts the calcium oxalate is present in such abundance that at times as much as one-sixth of the entire air-dried bark consists of crystallised calcium oxalate." ...

Another relevant influence is tannin. "All the exudations of the earlier members of the genus, as well as those of the closely related genus Angophora, contain the crystallisable body aromadendrin ... Economically this is of importance because the tannins in those species which contain eudesmin and aromadendrin in their kinos can be utilised for tanning purposes". One of the thoughts I had - lacking any knowledge of chemistry and how these chemicals develop over time in their natural state - is whether this is the same as the resins in the wood, and then whether these hardened resin veins we so frequently see in gums, create an abrasive compound?

Any thoughts?

Regards from Perth

Derek

Do you have access to a microscope? Might be illuminating to stain for certain clays and see if they show up in the wood structure. I just know that I have to sharpen all the time, not as often with PMV11, but laugh when Paul Sellers and the like say the they still need to sharpen "once or twice" a day. If only!

Just thinking about clay in the wood because most Jarrah grows in clay and they are very small particles which might be able to get into the wood.

I wouldn't know what to look for. This type of study must have been done before, surely.

I found an article on Australian Timber in an early Australian Wood Review mag, but it did not look at the issue of wear, only what timbers are available for furniture builders.

Regards from Perth

Derek

Derek,

I'm curious whether your recent experience working extensively with US Maple has led to this post...

All I can really comment on is my personal experience.

My experience shows that there is a correlation between density and Janka rating, but it's not a direct correlation. Gidgee is more dense than Buloke, but it has a lower Janka rating. I could probably find other examples, but that's a good one.

I do, however, find there to be a direct correlation between the density of a wood and the difficulty of pushing a plane blade through the wood. Harder plane pushing = decreased depth of cut = more strokes to do the job = more friction = more heat = faster blunting to achieve the same results. So given that the average density of Aussie woods is so high(almost all eucalypts, most acacias, most drylands stuff, etc.), I think you're likely to, on average, be sharpening more down there.

As someone who "cut my teeth", so to speak, on Aussie woods and has now moved back to the US where we claim some of the most workable woods around (specifically Cherry and Walnut if we're talking commercial stuff), the difference is pretty obvious, as far as I'm concerned. Even Maple and Oak, which guys around here act like you just absolutely are crazy to work by hand, don't really compare, in my opinion. I consider those two woods to be very workable, with the exception of Maple, which is prone to tearout in the right circumstances. It's like growing up in Queensland and moving to Tasmania and having to explain to the locals that "This isn't hot weather!".

On the topic of tearout, Aussie woods are pretty "cranky", to quote Terry Gordon. There is a lot of figured stuff happening down there. Figured wood means more shallow depth of cut, which means more strokes etc. Refer to previous paragraph for full equation... It also means a higher pitch or the use of a cap iron is necessary more often, which also increases the pushing difficulty and... well... see previous equation.

Anyway, good topic. I hope that input was worth something.

Cheers,
Luke

Hi Luke

Thank you for that post. Great for context. Yes, to answer your question, my recent experience with US hard maple and black walnut indirectly led to this thread. I mentioned on Sawmill Creek that I found those two timbers pleasant to work with. The hard maple was prone to tear out around knots, but a double iron soon fixed that. By comparison to West Oz timbers, these were wonderful timbers for furniture making. I really liked them (and am now building a sofa table in hard maple to compliment the kitchen cabinets I recently finished).

One forum member (on SMC) always takes issue with me mentioning how difficult our timbers are - that they are hard and interlocked, and wear tool steel quickly ... hence the preference among many in Oz for HSS and A2 blades over O1. He cannot understand why we do not use vintage high carbon steel only. He seems to think that I make it all up (that our timbers are hard on tools). Anyway, I did a little research, and was surprised that Jarrah was not abrasive due to high silica, as I had supposed. Obviously there is "something else", and I was wondering if it was more than just hardness.

Regards from Perth

Derek

Hi Derek

as I mentioned earlier you will to get anywhere with this will require a lot of data points. Perhaps even a meta analysis on the scale expected of a Masters thesis, but definitely undergraduate standard.

"Workability" is a subjective term and will comprise issues such as
difficulty of pushing a cutting edge through the wood -- i.e. morticing, saw cutting
difficulty of scraping a cutting edge over the surface -- i.e surface planning
propensity to tear out
propensity to blunt cutting edges -- but some references won't comment on this, perhaps because for many woods it is not an issue.

breaking workability down into what I think it is related to --
grain type -- straight, interlocked, reversing, ripple (e.g. tiger stripes)
reaction wood / little reaction wood
silica content

leaves lots of factors to be considered before you commence an in detail investigation

Thanks for your thoughts, Ian. Perhaps I could find a way to combine woodworking and psychology in another thesis?

I am only interested in wood blunting steel. Workability is not a focus. I think that we all understand the nature of interlocked grain, and hard and dense timber. I just wonder about possible chemical and other ingredients, and their effect on tool steel.

There's a PhD here waiting for someone.

Regards from Perth

Derek

I think that workability has to be your primary focus.
Unlike density or hardness or crushing strength, workability is qualitative (subjective) not quantitative (objective). As is descriptions of grain "type".

Along with a wood's propensity to tear out, workability also encompasses tool wear and cutting effort.

chasing silica content or clay mineral type and quantity are I believe just rabbit holes meant to distract you.

when you have some time chase up wear bevels on plane blades -- over the past 10 to 15 years there's been some blog discussion of same and the difference wear bevels make to the performance of BD and BU planes. Konrad Stiener blogged about the topic some years ago in the context of fitting stair treads, IIRC.

I suspect that the wood database has the data to draw some definitive conclusions comparing tool wear and effort to density / hardness and crushing strength.
time to assemble and analyse the data is really the issue.