About 5 weeks ago we moved the tree loppers yard and while packing up some of the lumber I sprained a two fingers on my right hand. I thought little of it at the time but in the last two weeks they have got worse, especially in the morning (can't put any pressure on or rotate my right hand or even open a water bottle) so I have had X-rays and have to go back the docs tomorrow.
In the meantime I have been messing about with a new materials testing unit at work.
With a simple mod I have been able to turning it into a timber hardness tester.
Sorry about the poor photos.
The tester is basically a computer driven press/stretcher that can pull or push on a material with the distance resolution of about a micron, while measuring the forces (up to 50 kN or 10,000 lbs) on the material.
It comes with a range of anvils and attachments - It's main use at the moment is to measure the compressive strength or new concrete geopolymers.
To perform a Janka Hardness test I needed a hemispherical dimple with a 0.444" in diameter dimple to compress the wood, and the other end had to mate to the tester's linkage system (a simple socket and steel pin arrangement). The dimpler (red arrow) I was able to machine up on my trusty Southbend in my home shop.
Here you can see it in action including a couple of test dimples in a bit of Aussie Hardwood.
In the image above you can also see some of the problems - like that big split generated by dimple A. The resulting Janka hardness was 6200 N (dry Jarrah is supposed to be about 8500 N) Some of the discrepancy is due to the MC, teh 8500 figure is at 12% MC and that piece is about 15% MC.
Dimple B came out to be 5300 N (Graph shown below) - The crushed edges indicates there was some sort of void or crack under the dimple.
Dimple C gave 6800 N probably because the crack from dimple A extended under C while dimple C was being formed.
The computer puts out a graph like this one for Dimple B - the Janka hardness is simply the compressive load required to generate a penetration of half the 0.444" ball (ie 5.82 mm)
The graph should be a straight line - when the graph kicks over a like this did in the middle, this indicates a problematic result.
Anyway - I'm still getting my training wheels with this machine.
One of the reasons I'm doing this is because I like messing about with new gear but I do hope to obtain some hardness data for many of our local timbers for which there is currently no data.
In the meantime I have been messing about with a new materials testing unit at work.
With a simple mod I have been able to turning it into a timber hardness tester.
Sorry about the poor photos.
The tester is basically a computer driven press/stretcher that can pull or push on a material with the distance resolution of about a micron, while measuring the forces (up to 50 kN or 10,000 lbs) on the material.
It comes with a range of anvils and attachments - It's main use at the moment is to measure the compressive strength or new concrete geopolymers.
To perform a Janka Hardness test I needed a hemispherical dimple with a 0.444" in diameter dimple to compress the wood, and the other end had to mate to the tester's linkage system (a simple socket and steel pin arrangement). The dimpler (red arrow) I was able to machine up on my trusty Southbend in my home shop.
Here you can see it in action including a couple of test dimples in a bit of Aussie Hardwood.
In the image above you can also see some of the problems - like that big split generated by dimple A. The resulting Janka hardness was 6200 N (dry Jarrah is supposed to be about 8500 N) Some of the discrepancy is due to the MC, teh 8500 figure is at 12% MC and that piece is about 15% MC.
Dimple B came out to be 5300 N (Graph shown below) - The crushed edges indicates there was some sort of void or crack under the dimple.
Dimple C gave 6800 N probably because the crack from dimple A extended under C while dimple C was being formed.
The computer puts out a graph like this one for Dimple B - the Janka hardness is simply the compressive load required to generate a penetration of half the 0.444" ball (ie 5.82 mm)
The graph should be a straight line - when the graph kicks over a like this did in the middle, this indicates a problematic result.
Anyway - I'm still getting my training wheels with this machine.
One of the reasons I'm doing this is because I like messing about with new gear but I do hope to obtain some hardness data for many of our local timbers for which there is currently no data.
At least it is only a few broken bones this time. 
