Too much grunt!

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?

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

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:

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

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.

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.

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?

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.

non skid step treads

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.

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.

Brmorgan said:

Bob, you using the same chain setup as always?

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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?

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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)?

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

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 ???

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

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 ???

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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.

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.

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 ????

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

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

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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.

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?