sawmill marring / marking lumber ripple discoloration... why?

[DPForumDog]

 

 
What would cause the sawmill blade to cause these ripple discolorations?    The dark generally wipes right off with a dry or wet rag.
Thanks

Granny DP
DPForumDog 

[trimguy]

Could it be not enough set and the blade body is dragging on the wood ?

[tylerltr450]

ripple is from tooth set. Staining is from metal reaction on the wood.

[Southside]

You have a tooth or teeth out of set, likely from hitting something, then you have metal stain. Oak? 

[DPForumDog]

Yes, it is red oak.
This only happened on a few.  We have milled about (50)  5/8 x 6 x 72 for a ceiling I want.  This only happened on a few?  We did change the blade in the middle of the sawing and I cant remember if these were before or after blade change.

[DPForumDog]

Could it be not enough set and the blade body is dragging on the wood ?

What does not enough set mean?  Is the same as a loose blade?  Someone else said we may have a bent tooth.

Thanks

[terrifictimbersllc]

Set is how far a tooth sticks out sideways from the body of the band usually .025 inches or thereabouts. The suggestion that there's not enough set would mean it more likely that the band would be rubbing on the wood compared to if the amount of set or greater and the kerf was wider so that the band is not rubbing on the wood. Band rubbing on the wood has to do with the stain you're seeing metal in contact with Oak or some other woods causes a reaction between the tannic acid in the wood and the iron in the band to give iron tannate which is black. The ripples it is being suggested have to do with a tooth sticking out further than the others, or perhaps a series of several teeth where they are not sticking out at all for example if thereThey were round it off and not as sharp or tall as the others.

[DPForumDog]

Thanks everyone!
I also found this great thread in the archives which was also very helpful!
https://forestryforum.com/board/index.php?topic=44535.msg641715#msg641715
Granny DP

[DPForumDog]

Could a  lack of lube be accentuating our problem? blue / black stain  ? We only use plain water in our tank, but I read that some people add dawn or diesel to their water tank.  I believe this is called lube? 

I read this on another thread and it resonated with me. 
I started using a diesel lube because the water lube was staining the seasoned post oak I was milling.  I mean lots of blue staining wherever the lube water touched the post oak.  Completely unacceptable.  So I tried the diesel lube and that solved the staining problem.  The diesel also eliminated pitch buildup on the blade and because I've got it set for 1 drip every 3-4 seconds, I use so little diesel that I can't even remember the last time I needed to fill the lube tank.  

The lube I use is actually a 50/50 mix of diesel and bar & chain oil.  I also keep a spray bottle of lube and use it all over the mill on anything that looks like it needs lubrication.

What do you think?  
Thanks 

[terrifictimbersllc]

You dont need water to get black stain from iron contacting certain woods. The wood is wet enough on its own. 

[DPForumDog]

We milled some more this afternoon and I still saw the blue black occasionally.  i think it is more apt to happen when we are taking a very thin skim.  (slighting shaving)  
I did discover today that if i brush the wood asap after the cut I can wipe the blue black metal reaction off.   I think i should have done that the other day because my theory is if you let the blue black dry then it is hard as heck to get off.  I left some blue black on a piece today and will let it dry a week to test my theory,

Thanks
Granny DP

[Magicman]

The blue/black is caused by the blade behind the teeth contacting the wood which is something that should never happen.  Dull blades will do it.

Lightly shaving the top of a cant will sometime cause the blade to sorta vibrate because the teeth on both sides of the blade are not engaged in the cut.  Shaving will also generally produce a ragged surface and I avoid doing it.

[ladylake]

 Something is putting out some metal, either the blade or the blade guides or both..  What kind of blade guides are you using.   Steve

[Endred]

Got the same color when I cut some oak with a chainsaw. Does the color penetrate deep into the wood? I`m worried about stains on the finished planed product:-)

[terrifictimbersllc]

Probably not if the stain is from short contact with a band.  Leaving wood on forks or wrapped with a chain hours or longer would be worse. 

The black color can be removed by sponging on a solution of oxalic acid in water.  Several applications rinsing off between will remove the black stain, at least fresh black stain, I have done this.  Not sure about removing it if it is left on through final drying of the wood. 

[Endred]

My boards have to be planed 5 mm or more anyway, so I hope it goes well without staining.

[esteadle]

Could a  lack of lube be accentuating our problem? blue / black stain  ? We only use plain water in our tank, but I read that some people add dawn or diesel to their water tank.  I believe this is called lube?

What do you think?  

It's the opposite -- too much water as lubricant when cutting oak. Plain water blade lubricant reacts and becomes acidic when it contacts the wood and sawdust being sawed. The acid reacts with the metal in the blade that it is also touching, causing a blue staining to appear. The sawdust picks this up readily as there is lots of surface area for the blue-tinged lubricant to be soaked up. But the boards will pick it up as well if left in contact. That is, if you leave the blue sawdust on the boards, it can migrate into the wood and penetrate the surface fairly deep.
I would suggest eliminating the water as your lubricant completely and trying it that way. You don't really need lubricant to saw wood anyway. It is mainly used to reduce the amount of fuel being consumed while sawing. It makes it easier for an engine to pull a blade through the wood. Others use hydrocarbons like diesel, or bar oil, or cotton spindle lubricant. I stay away from those, as my experience with those lubes seemed to accelerate the decay of my rubber parts (belts, hoses, hydraulic lines). 
Best of luck to you. 

[Stephen1]

esteadle, I agree about less lube. 
I read a post by Marty Parson of WM, who said to only lube the blade to remove any sap buildup, and turn the lube off before you enter the cut. I have been doing that a lot more now and like the way it works. 

[barbender]

Sometimes if you are having a blade issue, the body of the blade will rub on the cant. You'll see streaks immediately, and probably have a hump or dive there as well. If the blade rubs on an oak cant, it will stain like that.