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Timber properties of NZDFI's selected species

NZDFI's selected eucalypts are categorised as Class 1 or Class 2 durability in the Australian Durability Standard. They are markedly stronger (stiffer and denser) than radiata pine. The table shows examples of species which are part of NZDFI 's current breeding programme (E. bosistoana and E. globoidea), along with others which are being grown in our demonstration trials and which have potential to be incorporated into the breeding programme in future.

Species  Density @ 12% moisture content (kg/m3)

Stiffness

(GPa)

 In-ground life expectancy (years)
E. bosistoana 1100 21 > 25
E. globoidea 880 17 15-25
E. quadrangulata 1030 18 15-25
E. cladocalyx 1090 14 >25
E. macrorhyncha 635-955 no data 15-25
E. tricarpa 1130 17 15-25
Pinus radiata 480 9 15-25 (H4 treated)

Machinability of E. globoidea

Fourth-year School of Forestry Honours student Hamish Scown completed his Honours thesis on the machinability of E. globoidea.

Hamish used the industry standard (ASTMD1666-17) to undertake six tests of the machinability of 28-year-old E. globoidea timber sourced from Banks Peninsula, and compared the results with the same tests on radiata pine. The radiata pine had an air-dry density of 460 kg/m3, compared to the E. globoidea’s 723 kg/m3.

The tests were: planing, sanding, shaping (edging and grooving), boring, mortising and turning.

In general, the E. globoidea machined very well. Machinability was scored at various points in each operation, with the only low machinability scores occurring at certain points in some tests – for example as the tool exited the wood when grooving, boring and mortising.

The only significant difference in the results between E. globoidea and radiata pine was in the sanding operation, where 120 grit sand paper became gummed up, resulting in the wood surface being burnt. The problem was solved by sanding to 0.5mm depth instead of 1.2 mm, and a ‘Grade 1’ finish was achieved with the second approach.

Key messages from the study:

  • E. globoidea machined equally well or better than P. radiata, although sanding required a lower setting than that used to sand radiata pine.
  • There is no need for radiata-based solid wood processors to invest in new machinery when working with E. globoidea
  • Optimising processing techniques can improve machinability scores for E. globoidea
  • Within-species density is not a strong predictor of machining quality within a species.

A Technical Report is available with full details and more images of the project: Machinability of E. globoidea