dealing with insanely hard oak..

[thetyreman]

I've been chopping some dado joints today and noticed that the piece of oak seems even harder than normal, I heard somebody on here saying that this is the result of it being kiln dried? is that true, can it change the hardness of oak?

I literally am having to sharpen up after almost every joint and have never known anything like this piece, it's american white oak by the way. I am using narex chisels which (I think) is O1 steel, I also don't mind sharpening every 20 minutes but normally the edge lasts much longer than this.

any thoughts?

regards,

Ben.

 

[AJB Temple]

Very dry oak can be extremely hard. I am doing a lot of work on very well seasoned oak in my current kitchen build. I rotate 3 old (Ward) chisels that I use for mortice chopping after drilling out (these are big, deep mortices) and I give them a touch up every half an hour or so. I use a Robert Sorby linisher and it takes 10 secs per chisel. For this purpose I do not use a secondary bevel. I don't bother stopping unless I am doing very fine cuts to trim up right at the end.

Oak is very variable. Makes no difference if air or kiln dried - It can be very hard. I tend to see that as a good thing (hammer)

Keep at it. Adrian

 

[Trevanion]

Every tree is different. Occasionally you get unusually hard boards, occasionally you get unusually soft boards.

I'm no expert and I've yet to give Cut & Dried by our very own Sgian Dubh a good read (I will get around to it!) but I would assume growth conditions would make up for most of the hardness properties in timbers. I would assume a tree that's been grown on a rocky hillside fighting gravity and wind for its whole life would produce much harder timber than an identical tree grown in ideal conditions on flat, sheltered ground. I was once told by a proper old-school furniture maker that the reason some trees produce heavily rippled timbers is that they have grown in very arduous conditions like my example of a hillside, but I've also been told there's no real rhyme or reason for it so I don't really know the answer.

Perhaps change your bevel angle? Might last a little longer.

Welsh Oak in particular is a totally different animal though, extraordinarily hard, stubborn and a bit all over the place, just like the people :lol:

 

[D_W]

Add about 3 degrees to the bevel angle. If you're using a long single bevel, just round the tip over a little on the bevel side.

 

[D_W]

separate comment about the narex chisels - they're a little different than most. They're hardened with a different process that makes them less expensive to make, but they will come up short in hardness because of it (I'd imagine the newer higher priced once, this isn't the case).

The issue with the hardness isn't severe (they're spec at 59 instead of 61 or so that older chisels typically are, or footprint - when they were sheffield - or ashley iles), but what you're doing is exactly where you'll notice a softer spec chisel being a little softer.

Several years ago, I was making some cocobolo planes and I bought hard chisels to deal with them. It turned out to be a waste of money as what I got were japanese chisels, and they couldn't tolerate the mortising of the cocobolo at a reasonable angle. I ended up figuring out that chisels like the ones you're using do just fine with a few extra degrees rounding the edge over a little bit and you get through the work and no problem.

What you'll find in older magazine articles (and probably still now) is comparing a bunch of chisels at an identical spec and then declaring one the winner, but whatever the task is (if reasonable), unless chisels are absolute junk, a little bit of accommodation generally helps things hold up fine.

 

[Sgian Dubh]

I've been chopping some dado joints today and noticed that the piece of oak seems even harder than normal, I heard somebody on here saying that this is the result of it being kiln dried? is that true, can it change the hardness of oak. Ben.

As others have already noted, oaks, as is the case with all wood species, can vary in hardness because of a variety of factors, e.g., growth conditions, such as climate, soil, location, and so on. In every Bell curve the majority fit somewhere near the peak of the curve, with outliers at either end, and in this case we're talking of hardness, with the majority of pieces of oak of a particular species fitting somewhere close to the curve's peak. Yours may simply be an outlier at the hard end.

However, you mention kiln drying being a potential cause. It's true that wood kilned to a low moisture content (7% ±2% MC being the standard American target for furniture grade material) becomes stiffer and harder than when the wood was green, i.e., at fibre saturation point (FSP) and above. It's also true that kilned wood allowed to regain moisture from its kilned MC condition up to and above FSP will never be quite as soft and flexible as it was before in its original green state and before it was kilned. This is one form of hysteresis. I also suspect that the kilning of the wood in itself hasn't made it especially hard, but again, it's possible.

So, in your case I suspect you have a hard outlier, as I discussed earlier. I suppose it's also possible that your chisels aren't as tough as you think, and maybe they weren't tempered correctly; I suspect this is unlikely, and they may just be softer in general compared to other chisel brands and the steel they choose to use. I've no real information about that last bit as I've never investigated the subject of steel properties, e.g., hardness and its suitability for woodworking tasks. And lastly, as others suggest, maybe you might benefit from using a steeper sharpening angle on your chisels which should help with edge retention, at the cost of requiring a bit more force to drive the cutting edge through the wood, i.e., whack harder or more frequently with the mallet. Slainte.

 

[Woody2Shoes]

Every tree is different. Occasionally you get unusually hard boards, occasionally you get unusually soft boards.

I'm no expert and I've yet to give Cut & Dried by our very own Sgian Dubh a good read (I will get around to it!) but I would assume growth conditions would make up for most of the hardness properties in timbers. I would assume a tree that's been grown on a rocky hillside fighting gravity and wind for its whole life would produce much harder timber than an identical tree grown in ideal conditions on flat, sheltered ground. I was once told by a proper old-school furniture maker that the reason some trees produce heavily rippled timbers is that they have grown in very arduous conditions like my example of a hillside, but I've also been told there's no real rhyme or reason for it so I don't really know the answer.

Perhaps change your bevel angle? Might last a little longer.

Welsh Oak in particular is a totally different animal though, extraordinarily hard, stubborn and a bit all over the place, just like the people :lol:

All things being equal, a faster grown specimen will have a looser - and arguably weaker - grain structure. Round here, coppiced sweet chestnut grown on a north-facing slope could sometimes sell at a premium to the same stuff grown on a south-facing one. Slower growth, tighter grain structure, tougher and more durable material.

 

[thetyreman]

thanks for the input guys, I'll start with trying the higher bevel angle, I sharpen freehand so it may be closer to 25 degrees than I realise, I will have a play with higher angles and see if it makes a difference.

 

[AndyT]

Another approach is to put the hard bit back in the pile of wood which is going to be useful in a project that you will never get round to making... Works for me