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Is Janka alway right?

Webb Willmott

Webb Willmott

Joined
Feb 25, 2025
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This should be an interesting discussion. I recently posted a thread in which I used the term “rock hard walnut”. Probably not a best choice of an adjective (hard) but from my point of reference, the bottom of a lidded box seemed much harder than the top.

The top was straight grained but the bottom had much more figuring. Both pieces came from a box of ends and pieces and I tried to match the color more than the grain. Why was the bottom harder to turn than the top? Silica, grain, growth rings, different tree, tool sharpness, tool choice, etc…?

All I can tell you is Dad had a couple of walnut trees cut and kiln dried for use in his later years. After he passed, I inherited his wood pile. One thing I’ve noticed over the years, there is a great deal of variation of density and hardness between boards.

Maybe it’s just me.
 
I don't think it's just you, Webb-There can be so much variability in the structure of any given tree. The Janka measure is about as scientific a test as you can get for measuring the general hardness of a wood species, and I think it is mostly very accurate. For example, cedar is super soft and has a very low Janka rating, while something like desert ironwood or lignum vitae are rock hard and earn their numbers near the top. But I got a very special dried platter blank from the DeHeers of Oregon black walnut that was noticeably softer and lighter than the Eastern variety I have turned a considerable amount of. I posted pics of it not too long ago; it had considerable figuring and colors that were mostly quite soft, with some really hard burl eyes here and there. I gave up trying to sand it evenly on the lathe, and just did the last few grits up to 800 with flexible sanding pads so that I could feel for humps and unevenness.

Part of what I love about turning wood is the potential for surprise. When you cut into a log or blank, it's like Forrest Gump said, "You never know what you're gonna get." Anyway, I take the Janka scale as a mostly very accurate general measure, and enjoy the surprises when a particular blank varies from what it is "supposed" to be.
 
A product of nature is no different than humans. No two are alike. My reply is based on nearly 40 years of turning and 53 years of furniture making. I’ve owned a sawmill and even purchased hundreds of board feet of walnut. I’ve never seen nor heard of anyone claiming their walnut is harder than anything on the Janka scale and could only be compared to stone. Weigh the boards and you will at least know the density difference.
The Janka wood scale is not based on the density of a square foot; it measures the force required to embed a steel ball halfway into a piece of wood. The Janka rating is a numerical value representing pounds-force (LBF) or pounds per square inch (PSI) needed for this specific test, not a measure of weight per unit of area. My anecdotal story about a wide spread density is a 2x14” piece of white oak. It has to be at least double the density of a normal white oak board. That board was given to me about 35 years ago. I better use it while I can still lift it!

 

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Webb Willmott said:
One thing I’ve noticed over the years, there is a great deal of variation of density and hardness between boards.
Click to expand...
Not only between boards, but within the SAME board, even at a spot a short distance away. But as mentioned, the numbers are really helpful when comparing species.

Aaron Harris said:
it had considerable figuring and colors that were mostly quite soft, with some really hard burl eyes here and there. I gave up trying to sand it evenly on the lathe, and just did the last few grits up to 800 with flexible sanding pads so that I could feel for humps and unevenness.
Click to expand...
This is where I find curved hand scrapers really shine. They make it easy to remove the hard, high spots. And unlike sandpaper, especially when backed up by flexible pads, steel scrapers don't lower the soft areas. And banish tool marks to another dimension.

I've had far better final surfaces, and with less effort, in the years since I started making and using custom scrapers.
I've made dozens of scrapers in different shapes and sizes, ground from cabinet scrapers and sharpened the same way.
If anyone want's to try this, come visit. If you find it useful I'll make you one.
1760924058316.jpeg
After scraping, the one from Eastern Red Cedar (at the top) needed only 600 grit sandpaper, backed up with a firm but flexible "Magic Rub" white eraser.

I call it a soft sanding block, flexes to follow the curves, easier to hold and works better than folded sandpaper. This one has coarse paper wrapped around:
1760924559923.jpeg

And discovering StewMac scrapers made smoothing some curves even easier..
1760924399754.jpeg IMG_7499_e.jpg

Ok, I'm off my scraper soapbox, For now....

JKJ
 
Nope.....

I asked a question to AI, "is late wood harder than early wood". This is the answer.

Latewood is harder than earlywood because it has thicker cell walls and is more densely packed. Formed during the slower growth period of the summer, latewood provides rigidity and strength to the tree. In contrast, earlywood is formed in the spring and consists of larger, thin-walled cells, making it less dense.

Now as a 30 year sawmill operator (hobby part time), Tree Farmer, and 60 year woodworker this is my opinion. Walnut trees love water and nutrient rich soil. If a walnut tree is growing on a south facing slope in much of the country the growth will be very slow. In a forest with lots of competition for sunlight it will also grow slow. Due to the poor growing conditions it will not put on much earlywood but will have the same amount of the harder latewood. Count how rings to the inch it has, 5 rings is fairly fast and soft. 10 rings or more to the inch is slow growing and will be harder.
 
Richard Coers said:
hard as a piece of rock
Click to expand...
Concerning stone, has anyone else turned alabaster?

When cruising the shops in Volterra, Italy we saw lots of things turned from alabaster and bought some things including a small lidded bowl. I brought back a few good-sized chunks to play with.

I also brought back a few rather crudely-made alabaster bottle stoppers with corks glued to the flattened bottoms. I removed the cork on one, drilled and tapped a hole to fit Niles stopper hardware, and turned a much better shape (IMHO) and smoother surface. Used Thompson tools. It was easy to turn and with some fine sanding and a little wax it looks great. I should take a picture.

JKJ
 
John K Jordan said:
Concerning stone, has anyone else turned alabaster?

When cruising the shops in Volterra, Italy we saw lots of things turned from alabaster and bought some things including a small lidded bowl. I brought back a few good-sized chunks to play with.

I also brought back a few rather crudely-made alabaster bottle stoppers with corks glued to the flattened bottoms. I removed the cork on one, drilled and tapped a hole to fit Niles stopper hardware, and turned a much better shape (IMHO) and smoother surface. Used Thompson tools. It was easy to turn and with some fine sanding and a little wax it looks great. I should take a picture.

JKJ
Click to expand...
I took an art class a long time ago. We cut chucks of alabaster with a wood cutting handsaw to carve small sculptures. Cut really nicely. Soapstone cuts incredibly easy and very easy on a gouge. Just dusty. There is that old saying, “What is the best lathe for turning stone?” “Someone else’s"
 
John K Jordan said:
Not only between boards, but within the SAME board, even at a spot a short distance away. But as mentioned, the numbers are really helpful when comparing species.


This is where I find curved hand scrapers really shine. They make it easy to remove the hard, high spots. And unlike sandpaper, especially when backed up by flexible pads, steel scrapers don't lower the soft areas. And banish tool marks to another dimension.

I've had far better final surfaces, and with less effort, in the years since I started making and using custom scrapers.
I've made dozens of scrapers in different shapes and sizes, ground from cabinet scrapers and sharpened the same way.
If anyone want's to try this, come visit. If you find it useful I'll make you one.
View attachment 80592
After scraping, the one from Eastern Red Cedar (at the top) needed only 600 grit sandpaper, backed up with a firm but flexible "Magic Rub" white eraser.

I call it a soft sanding block, flexes to follow the curves, easier to hold and works better than folded sandpaper. This one has coarse paper wrapped around:
View attachment 80595

And discovering StewMac scrapers made smoothing some curves even easier..
View attachment 80593 View attachment 80591

Ok, I'm off my scraper soapbox, For now....

JKJ
Click to expand...
I keep meaning to try this scraping on a finished piece, John!
 
 
Matt Estlea, a fine woodworker, just did a video about rare and exotic woods, and he tries to pronounce the Latin names, and mentions Janka Hardness. I would expect the "actual" hardness to vary a lot, depending on growing conditions mostly. With his video, I was surprised by how many woods can be "restricted" now. Well, not surprised actually, more like "should have seen that coming".

robo hippy
 
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