# Too much grunt!



## BobL (Jul 5, 2009)

I've been busy at the day job for the last 2 months so not too much time for milliing. So far I have only milled a couple of 40"+ logs with the 880 on the BIL mill with the 60" bar. I've generally been quite pleased with the way the mill and saw are running and the finish has been excellent.

Today I decided to tackle a small 20" diameter lemon scented gum with the 42" bar and 3/8 10º top plate chain.

Here's the setup. 






Given this is very hard wood the milling speed was pretty quick but it's also the worst washboard I have ever seen in hard wood.

Here is what happened when I pushed the saw.










I would have thought the low top plate angle would have had more of an affect as the finish is way better on the wider logs.

Maybe it's just a case of too much grunt for such a small log?


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## lmbeachy (Jul 5, 2009)

BobL.I noticed the same effect on my hommade logosol mill whne I mill a small soft log. The washboard effect is much more pronounced. It seems to be that the bar is moving forward at a much faster rate in relation to the speed of the chain and leaves a rougher cut. Lmbeachy


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## Ted J (Jul 5, 2009)

DAMN IT MAN.... looks like you'll have to charge extra for the "custom texture" that you've applied to the surface of the board.:greenchainsaw:


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## oldsaw (Jul 5, 2009)

I've never seen anything like that before. I had a chain with a couple of bad teeth after contact with a 20d nail, and even it didn't do that bad. I eventually tossed the chain since I could't find the "culprits".

My only guess is pushing it too hard. Did you measure the driver guage? .50 chain in a .063 bar?

Mark


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## glennschumann (Jul 5, 2009)

I've had the same problem with small logs, particularly the soft woods. (24" bar) I tried a new chain, and that did not help, I tried a new bar, and that did not help, but a new chain with new bar did make things better, but not as nice as my well worn 36" bar and chain, or my 42" bar and chain. I did notice that as the chain dulls, if you lean on the mill, the cut will smooth out... as if the chain is firmly riding on the rails, not bouncing around.

I run an 066 / 36" mill.

I don't know if the short bar (24") has anything to do with it, but I'd like to figure it out. Next time I mill with that set up, I'm going to try setting my chain "a little too tight" for a cut to see if that helps any. This one has me perplexed too.


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## Brmorgan (Jul 5, 2009)

Bob, you using the same chain setup as always? Because your boards usually look so nice and smooth! That looks the same as a couple cuts I've made with full-chisel skip chain left filed around 25°. You sure one of the cutters didn't take a knocking during transportation etc. and get bent out sideways a bit? Or, if it isn't the same chain as always, is it possible you're accidentally using an .058 chain on an .063 bar (or something similar)? Because I had that happen with the small .325 setup that was on my 288XP when I got it - there was .050 chain on an .058 bar and it wouldn't cut straight or smooth no matter what I tried - kept climbing up out of the cut.


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## SilverBox (Jul 5, 2009)

I think it has to do with all that extra chain thats out of the cut, because when I cut smaller soft stuff I get that same effect (like 10-12" pine using a 36" bar), but not always, seems like the greener it is the less washboard I get. 

How dry was that log Bob?


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## Coalsmoke (Jul 5, 2009)

I agree with Brad, something is really out of whack, like a bent tooth. I run a skip tooth 25 degree chisel on my 395xp on my carriage mill and produce some really smooth stuff. I had something similar happen once and I think what happened was I hit a small rock, it dulled a few consecutive teeth and therefor the next cutter after those dulled teeth was having to take too much of bite and it was disrupting the way the teeth were tracking. I will try to attach a picture of the smoothness of the 25* chisel skip tooth I get. This is in douglas fir, but in a medium hardwood like Alder it can be even smoother.


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## texx (Jul 5, 2009)

non skid step treads


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## dave k (Jul 5, 2009)

I think you are correct in "to much grunt" in this case Bob, I suspect to much movement of the chain on the non cutting 20" of bar which set up a kind of vibration ?

With the 076 in a similar set up the lower revs would not have caused the same effect ?

I've noticed this effect whilst using a large saw and bar just cutting up smaller stuff like wet beech in particular.


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## BobL (Jul 5, 2009)

Chain was fine, no bent/damaged teeth. I stopped to inspect and touch it up after 4 slabs. It was set a little more aggressive (13/64 file) than normal.

I could reduce the washboard effect by not pushing the saw - the pictures I posted are where I just wanted to see how bad I could make the washboard effect. 

I might take one of my 42" chains and file the top plate to 0º and see what happens.


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## BobL (Jul 5, 2009)

Brmorgan said:


> Bob, you using the same chain setup as always?


Yep - same setup, it's a different chain of course because its for the 42 as opposed to the 60" bar.



> You sure one of the cutters didn't take a knocking during transportation etc. and get bent out sideways a bit?


Yep - it's clean as.



> Or, if it isn't the same chain as always, is it possible you're accidentally using an .058 chain on an .063 bar (or something similar)?


My only other chains are 050 and they are all 24" loops or smaller.


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## texx (Jul 5, 2009)

ok i have not done any milling yet but just wonder if this affect could be from or made worse by using a bar that is a lot longer than needed for the log being cut , as in a harmonics type affect, or with the amount of free bar or unsupported bar flexing up and down as the chain works.
would be interesting to see if it still did the same thing with same saw same chain cutter angle but shorter bar ???


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## jredjim (Jul 5, 2009)

I have noticed this also but it is only when i run a rip chain, i have never seen this with full comp at 10deg


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## BobL (Jul 5, 2009)

texx said:


> ok i have not done any milling yet but just wonder if this affect could be from or made worse by using a bar that is a lot longer than needed for the log being cut , as in a harmonics type affect, or with the amount of free bar or unsupported bar flexing up and down as the chain works. would be interesting to see if it still did the same thing with same saw same chain cutter angle but shorter bar ???



Having milled stuff from 12" to ~50" with different size bars and different top plate angle chains I have never seen so much washboard effect before. The difference here is using the muffler modded 880. Even though lemon scented gum is relatively hard this saw/mill just flies thru this small wood and because it doesn't bog down easily it's tempting to push it even harder. If I hold the saw/mill back the washboard effect is reduced but that is more work than just letting the saw do it's thang, the more I was pushing the worse the washboard. I think maybe it's a case of too much power in too small a log and the temptation to push a bit harder is irresistible. The guys that use a Lucas slabber see a similar effect.

BTW my rakers are now at ~0.040" - cut's like a demon and doesn't seem to slow the saw down at all!

Oh, one more thing on that first picture. Look at how far away from the log the saw/muffler flings the saw dust. It's even more significant on a big log so no more walking back and forth in a big pile of sawdust.


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## LAndrews (Jul 5, 2009)

I know Bob's a highly accomplished sawyer and doesn't need newb advice, but...

That looks pretty much exactly like the problem I was having the first time I milled a log. In hindsight, I recognized but didn't fully get that pushing harder made the problem a LOT worse. That was relatively soft and very dry chestnut...if it matters.

Turned out the bar groove had worn wide at the outside and the chain had worn a tad narrow. Chain could wobble around and would follow whatever was leading it. 

Replacing the bar & chain made the problem completely go away. 

I wonder if flipping the bar would help? It turned out that only one side of my original bar was NG and the other side just might be okay - haven't tried it since I've got a new one already.


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## texx (Jul 5, 2009)

bob if its to much grunt what about the guys that use 2 090 power heads on a double ended bar , i saw a video some where the other day of twin 090 saws on a mill and the operators were pushing it through fairly hard but having said that i never saw the slab once it was cut ,it could of been wash board looking too .
also do the guys that are slabbing real soft stuff have the wash board problem , i don't know ????


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## FJH (Jul 5, 2009)

Too much tooth angle and slopy rail will also cause that!


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## billstuewe (Jul 6, 2009)

> as in a *harmonics* type affect, or with the amount of free bar or unsupported bar flexing up and down as the chain works.


I also have had this happen. The first time was when I was using Bailey's ripping chain--.50ga--16"bar on 066--It cut fine at high revs but when the saw would lug down just a bit, I would notice the chain at the tip feeding into the cut doing a funny "wave", as if it were a bit loose in the bar. When I removed the board, there was the washboard just like in the picture. BUT--at the speed the chain is moving each tooth would rake across the cut at a right angle and this washboard is at a pronounced angle to the bar. Therefore I had also determined this to be some sort of a harmonic vibration. BobL, you say it is worse when you pushed hard--was that when your RPMs slowed a bit? (Mine would go from about 10200/9800 to 8500/8000 and the washboard occurred at the lower RPms) This cannot be from a bad tooth because it is at an angle to the tooth movement. It appears to be caused by a ripple effect on the teeth (harmonic vibration?). I closed the bar rails a bit so the chain could not "wobble" and it went away. My conclusion is that it is caused by the drivers worn/bar rails worn or spread allowing a bit of slop in the chain. Watch next time to see if you notice the chain entering the cut doing that little wavey dance.


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## DaltonPaull (Jul 7, 2009)

Looks exactly the same as a phenomenon I get resawing with my shop bandsaw once and a while. I'll be feeding a piece of wood and all of a sudden it's gets really easy to push it through the saw so I feed faster and the result is a twisted washboard just like in your picture. I haven't been able to figure out what causes the pattern for sure though. Maybe some blade resonance? I bet if you asked some band sawmill operators they might have a good guess. I wonder if your whole bar could be resonating back and forth?


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## billstuewe (Jul 7, 2009)

> I wonder if your whole bar could be resonating back and forth?


Nope--Its a 16" bar with about 3-4" of bar sticking out the far end and I can see the *chain* start to do a "wave" as it enters the wood.


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## Brmorgan (Jul 7, 2009)

Low RPM can cause this problem (at least in my experience) with full-chisel chain left at ~25°. I think it has something to do with the sharp point of the cutter wanting to bite in sideways if the saw isn't pulling it fast enough. Even a nice, tight bar can allow some fairly significant play in the chain, and the chain by its nature can flex sideways a bit.


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## BobL (Jul 8, 2009)

billstuewe said:


> Watch next time to see if you notice the chain entering the cut doing that little wavey dance.



Yep I have seen the wavy dance and I also think it's a harmonic thingo, but rather than harmonic - which is one vibe frequency causing another - I now think it's more related to chain wave, cut rate and cant width synchronization.

For those that do not know, the cutters on a sharp chain do not act like little planes riding hard up against the bar and all making little shavings in a row - that does happen the chain is blunt and makes powder instead of chips. What happens when a sharp cutter grabs is, it is pulled into the wood to a depth determined by many factors and in doing so is pulled off the bar by around a 1/4". This cutter cuts a leading channel and one or more cutters trail behind it, cleaning up that channel but also doing very little cutting in the process. This action forms a triangular shaped wave on the chain which also propagates a pulse back up the chain out of the cut and can be seen as the "wavey dance" described by Bill above.

The wave length of the cutting wave will be different from the wavey dance. The wave length of the cutting wave depends on things like the raker depth setting, hardness of the wood, chain tension, cutter hook, chain length etc

If the log is narrow and the revs are right there is the possibility the cutting wave and cutting rate can synchronize with the wavey dance.

So if the cutting speed synchronizes with a cutter reaching the peak of the wavey dance just as it enters the wood this cutter can cut a fresh new channel and trail sufficient cutters behind it to make a single clear ripple in the wood all in the time that it takes for the bar to move forward that distance. So the cutter can start about 1/4" off the bar as it enters the wood and is down on the bar as it exits.

At 9000 rpm a 3/8, 7 sprocket chain speed is 800"/s
The forward cutting speed is around 1"/s
The wavelength of the wood ripple is 1/4" so one 1 wood ripple sees 200" of chain. which for a 42" bar is around 3 chain lengths worth.
It sounds like a lot of but the lovely big chunky chips that the saw was making under these conditions is consistent with this idea.

The narrowness of the log also means the cutter gullet does not fill completely. On a wider cut the gullet fills and quickly pulls the cutter away from the wood - this stops the cutter from continuing to make a channel and which is why it does not make as clear a washboard pattern as it otherwise wood.

Clear as mud?


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## Brmorgan (Jul 8, 2009)

Bob - have you tried an 8-pin rim on that 880 in the smaller stuff (say under 30" dia.)? It should handle the load fine.


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## billstuewe (Jul 8, 2009)

BobL, I like your thought process--Too bad you are so far away--I would love to get together with you and make some sawdust. Now if you would put that thought process to work and let me know how to keep this from happening. It seems to do it worse with some chain. Two Saturdays ago I was milling willow--about 15" logs and several times I would get one deep groove all the way across the cut. It was exactly like the washboard cut you pictured but it was only one single groove. Very strange???


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## BobL (Jul 8, 2009)

Brmorgan said:


> Bob - have you tried an 8-pin rim on that 880 in the smaller stuff (say under 30" dia.)? It should handle the load fine.



Yeah I have the 8-pin sprocket - I'll have to give it a try!


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## BobL (Jul 8, 2009)

billstuewe said:


> BobL, I like your thought process--Too bad you are so far away--I would love to get together with you and make some sawdust.


I move around a fair bit so, never say never . . . . it could happen




> Now if you would put that thought process to work and let me know how to keep this from happening.


I'm working on it!



> It seems to do it worse with some chain. Two Saturdays ago I was milling willow--about 15" logs and several times I would get one deep groove all the way across the cut. It was exactly like the washboard cut you pictured but it was only one single groove. Very strange???



If while milling you slowly put pressure on the saw and slow it down there's a chance that it will pass through that synchronization speed and just do one big ripple as it passes through the wood as I describe.


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## Kicker_92 (Jul 8, 2009)

BobL said:


> Yeah I have the 8-pin sprocket - I'll have to give it a try!



Bob, what sprocket do you usually run on your 880? I'm using an 8-pin with the 3/8" chain as well, but haven't tried any other combinations.


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## BIG JAKE (Jul 8, 2009)

Maybe just out of practice Bob?  Good to see you milling again anyway! opcorn:


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## BobL (Jul 8, 2009)

Kicker_92 said:


> Bob, what sprocket do you usually run on your 880? I'm using an 8-pin with the 3/8" chain as well, but haven't tried any other combinations.



Because our wood is so hard I have only used the 7 pin 3/8 with the 880. This also makes sense with the the 60" bar. I have an 8 pin for for the 42" but haven't tried it out yet.


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## Brmorgan (Jul 8, 2009)

billstuewe said:


> BobL, I like your thought process--Too bad you are so far away--I would love to get together with you and make some sawdust. Now if you would put that thought process to work and let me know how to keep this from happening. It seems to do it worse with some chain. Two Saturdays ago I was milling willow--about 15" logs and several times I would get one deep groove all the way across the cut. It was exactly like the washboard cut you pictured but it was only one single groove. Very strange???



This happens to me if I almost stall the chain. I posted this pic in another thread last summer because I couldn't figure it out at the time either:







After a few more cuts the next day I realized it only happened when the saw engine bogged out to really low RPM. This was cut using 3/8 full-chisel @ 25°, 28" bar in 16-18" of wood.


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## deeker (Jul 8, 2009)

That pic is similar to what happens with the band-saw mill, if I have to stop pushing while cutting....

With the band-mill, I believe the cutters widen out as the rpm's go to a stop vs full speed......

It is easy to see where I have stopped while cutting...to adjust a dog or trim the log a bit.

Kevin


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## BobL (Jul 12, 2009)

*7 days later*

Same mill, same chain (but with 2 stroke file touchup), same wood - but log is about 30% wider. 

Last week on left - today's on the right!


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## BobL (Jul 12, 2009)

*Few milling pics*

Nothing special - Just had a mate (forum member Martrix) handy with a camera to take a few pics of me milling a small lemon scented gum.
On days like these it's hard to believe we are in middle of winter.


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## texx (Jul 14, 2009)

so what was the problem 2 stroke file touch up fixed ? did you change the angle a wee tad or just needed a sharpen ,or a bit more off the rakers ?


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## BobL (Jul 14, 2009)

texx said:


> so what was the problem 2 stroke file touch up fixed ? did you change the angle a wee tad or just needed a sharpen ,or a bit more off the rakers ?



Rakers weren't changed. I don't think the two strokes touch on the cutters wouldn't have changed much - the biggest change was the width of the log being cut ie 30% wider. That means the chain speed would have been out of synch with the wavey dance thing that billstuewe refers to - well that's my guess anyway.


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## Brmorgan (Jul 14, 2009)

I think it's probably a chain speed issue too. I once cut a 7" wide piece of pine with my 090 & full-comp .404 rip chain. It cut as fast as I could push it through the log, but produced a washboard cut even worse than yours. On a 30" spruce log though, it was almost as smooth as some finished lumber.


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## SilverBox (Jul 14, 2009)

BobL said:


> the biggest change was the width of the log being cut ie 30% wider.



Yup I agree. I've seen this before where you cut with alot of chain out of the cut and then go to a bigger log and it smooths right out.


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## dancan (Jul 14, 2009)

BobL said:


> Same mill, same chain (but with 2 stroke file touchup), same wood - but log is about 30% wider.
> 
> Last week on left - today's on the right!



Reminds me of machining a rotor , if the setup was a little off or just the right conditions you get similar marks on the rotor from the cutter vibrating at the right harmonics (don't know if this helps but I thought I'd throw it out there) .


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## BobL (Jul 14, 2009)

dancan said:


> Reminds me of machining a rotor , if the setup was a little off or just the right conditions you get similar marks on the rotor from the cutter vibrating at the right harmonics (don't know if this helps but I thought I'd throw it out there) .



Next time I find a suitable tree I will cut a long wedge and see what width this effect starts to kick in at.


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