Janka and all that.

[MJP]

I continue to collect odd unidentifiable bits of wood and, having given up any hope of actually being able to put a name to many of them, instead I wish to simply characterise them.

I make a nice sample piece showing side and endgrain; I can measure the SG easily enough of course; but I also wish to be able to measure the hardness.

I've failed to find any source of Janka hardness test equipment - though no doubt it would be far too expensive for me to contemplate purchasing simply for my hobby interest.

I've seen You Tube home-made Janka hardness testers, but really I can't afford the space for something which would be used for just a few minutes every so often.

What I would like is to use some kind of small pocket-sized hardness tester, similar to those used for testing rubber hardness and so on.

Obviously this would not be on the Janka scale, but it would be sufficient for me to make my own hardness comparisons.

Has anyone ever tried using, for example, a Shore rubber hardness tester on wood? Or anything similar? Or has anyone seen a comparison between Janka and any other standard hardness scale?

Martin.

 

[novocaine]

the issue you'll have is anything that has a smaller area than that used by the janka test is going to pass between growth rings and not give you a true reading (there is a reason the janka test uses a 0.444" ball). making a hand hardness tester using the right size ball is going to be useless above pine as your well out of the possible force you can apply by hand.

the shore tester tip is considerable smaller than required.

you can make your own tester with a load cell and a steel ball, you'll need a force amplifier for it to be useful (think big screw) and have a way of measuring the depth of the ball (or a line half way up it), by the time your done it might not be worth bothering with.

you are also correct in thinking the cost of a really tester is well out of any of us mere mortals to purchase (3k is the cheapest I've found in my bank of catalogs)

 

[MJP]

Ah yes - ball size.

I'd forgotten about that - obviously the test ball has to be big enough to average out across several growth rings.

That puts paid to the "pocket sized" tester then.

A poor man's Janka tester can be made from a press a la Machine Mart and the appropriate sized steel ball, but I don't want to make something that big - I'm pushed for space.

Looks like I can forget this brilliant idea!

Thanks anyway Novo - you've saved me wasting even more of my time on trivial persuits.

**

The UV torch I bought from ebay has just arrived so I'll try checking wood fluorescence instead methinks.

Martin.

 

[ED65]

Would the pencil test be of any help to you?

 

[MJP]

Thanks Ed -

This gives me food for thought. I'll give it a try.

I could also assemble a collection of materials of varying hardness to do a scratch test - something similar to the set of Japanese hardness files used in engineering.

Scribers made of HDPE, Polycarbonate, UPVC, and so on.

Excellent.

Thanks again,

Martin.