What causes this surface, grain or blade ?

[Tom the Sawyer]

Milled a small log yesterday and found this pattern on the cant.  Had a similar occurance once about a year ago.  Both times I was sawing ash.  Milled 11 other logs yesterday without any hint of a similar pattern, both before and after this log.  Last time I was using a TK Ultra Max 10° blade, this time a WM 7° blade.  The only thing that sounded any different was a slight change in the 'hiss' of the blade.  Is this an unusual grain pattern or is it symptomatic of something with the mill?


 


 

Thanks for the help,

[ladylake]

 I've seen that also mostly in basswood, has to be the grain.  Steve

[hackberry jake]

I think its a harmonic blade vibration effect.

[Magicman]

I occasionally see it when sawing harder species such as Oak, but I have never seen it extend to the length that you show.   For me, it will often show up within the first 18" upon entering the butt of a log, so the log's hardness is a factor.   

Now if you could intentionally do it to kinda replicate circle saw marks, you would have a winner.   

[barbender]

Whenever I've had marks like that my feed speed is too slow, FWIW.

[Dave Shepard]

Whenever I've had marks like that my feed speed is too slow, FWIW.

Same here. I think that is why it usually shows up in the first foot or so for me. I haven't seen an entire log look like that. Also more prevalent in wider cuts.

[ladylake]

As mentioned I see the often in basswood, no slow feed rate .  Looking at the saw marks on that cant looks like Tom is moving right along for ash.   Steve

[Macgyver]

I had a whole reply all typed up and ready to send, got distracted and 5 more came in in the mean time.  My post is summed up by pretty much saying ditto to these others.  I've noticed the pattern when my blade tension isn't high enough.  And, I've found that the pattern changes with my feed rate...another hint that it's due to the band.

[Chuck White]

Once in a while I'll get a similar pattern, but it's usually within the first 3-4 inches of entering the log/cant.

There have been a few posts posted, discussing this issue in the past!

[tyb525]

In the 2nd picture looks like there could be a little burning from the band, also caused by a slow feed rate. Slower feed rates tend to let the band vibrate more.

[Tom the Sawyer]

Just as additional information, I tried slowing down and speeding up to the point of bogging the engine down.  This log appeared to be limb stock, started out at 9" diameter by 5'7" long, the pattern was on all sides, the cant was 8" wide.  I've seen the patterns if I enter the cut at the wrong speed, this is different.   :-\

Just to clarify, the blade tooth pattern is directly perpendicular to the cant, the pattern I am curious about are the diagonal markings which are at the same angle (about 45°)on all sides of this cant but none of the other ash logs I sawed that day.   There was no noticeable head vibration, using the normal amount of lube, and the tension was consistent.  It wasn't my log so I don't have any to play with (like running it through a planer).   :-\

Client thought it was an interesting look but if it something within my control I'd like to know how to prevent it.  I only milled another 75 bf on this blade before i finished so I'll set up here at home and see if I can recreate it although I don't have any ash to mill.   

[Kansas]

Its curl. It should bring premium price. It is not the blade, and that stuff can be a bear to cut.

[ladylake]

 Now we're on the right track .  The pattern also shows up after planing which really elimates anything to do with the blade or feed speed.  Steve

[mad murdock]

Curly grained wood does bring a premium price, especially with Luthiers, if it is the right species for their instruments.  wood workers like it as well, it is real nice looking grain when finished! Lots of character.

[Peter Drouin]

Was it a old log or new green one, and did you make 1" boards and did they have the same thing

[Tom the Sawyer]

I think the trees came down in January of this year.  The boards in this cant were sawn at slightly over an inch.  All of the boards from this cant had the same pattern.  These trees were taken down as part of a construction project. 

They were landscape plantings around a library, not native or forest trees. They were healthy and not that large, the biggest ash butt log was about 16" diameter.  The rest of this particular tree may still be in the pile.  There are about 25 logs left to saw in this project, a mix of pin oak, sycamore, and ash.

[Ga Mtn Man]

Tom,

Interesting.  Did the pattern vary at all with your feed rate?  I have seen a similar pattern left in the sawdust on a cant, although at a much sharper angle:



 

[WDH]

Hopefully you will find some more logs like that one in the pile.

[beenthere]

This log appeared to be limb stock,

And may thus be part or most of the explanation. In one pic, the ring pattern was pretty abrupt steep (2nd pic, left side).

[WDH]

BT,

Looks like where a live limb branched off, maybe.

[tyb525]

If that is curl, it looks really uniform (evenly spaced). I have heard of curly ash, I know every species can have curl. Will be a bear to plane! Drum sanding would be better.

[Brucer]

It has the sort of pattern you'd see with harmonic vibration of the blade. However, I've never seen the vibration marks anywhere close to 45 degrees. I've also never seen it run the whole length of a cant. It usually appears in short lengths, with clean cuts between them.

[beenthere]

Maybe a bad bearing? Thinking it could resonate the band for the harmonics at certain speeds, ?? 

[Okrafarmer]

I milled some leyland cypress recently and it mostly did that, too. I didn't take any pictures though. My phone camera bit the dust and it's a lot less convenient now for me to take pics and post them.

[giant splinter]

It has a nice effect, The only time I have seen anything even close was when I milled some cottonwood, rift cut for a trailer deck.

[Jay C. White Cloud]

I think its a harmonic blade vibration effect.

Hello Hackberry Jake, 

Great observation Jake, and you are correct this is "harmonic saw pattern," indicant, often triggered by the combination of speed (fast or slow), the angle of grain upon entry in the cut, and homeostasis between the two.  I have achieved same, on rare occasion, with hand made Japanese saws, the correct speed in ration to the angle of approach and grain of wood cut.  I've also been able to reproduce the effect with chain saw mills more readily.

[tyb525]

I've seen the pattern too on my own mill, just like that, although I don't think it was the whole length of the log.

[Jemclimber]

Listen to Jake and Jay, although that log may have some curl I don't yet see, those straight marks are caused by the saw and not the log.

[Okrafarmer]

I think it is similar to "power hop" in four wheel drive vehicles.

[Kansas]

The more I look at that pic, the more I am convinced it is curl, and here is why. A woodmizer, or any of the bandmills, does not move fast enough through the log relative to blade speed. If you ever had a blade with a tooth out of whack, I doubt you move more than 1 inch per revolution. And that generally looks nearly perpendicular to the log. These are much more slanted. How would you get that spaced so evenly across a log? You would have to have tremendous forward speed to accomplish that.

[Dodgy Loner]

No way that is curl. Hackberry Jake and the others who suggested harmonic vibration are on the right track. I've seen that pattern before, but that is the most regular and prominent I've even seen it.

[Jay C. White Cloud]

I couldn't say 100%  that "curl," grain wouldn't cause it, but I have milled and sawn much curl grained species, and have never had a "harmonic response."  I have had "harmonic patterns" show in just about every wood I have sawn from soft wood to hard, and it has always been due to a combination of factors, not just grain pattern.

[Magicman]

Tom stated in a previous post that the normal tooth drag marks were 90° to the cant as they should have been.  These marks are at 45° and appear to also be tooth marks.  The surface appears to be very rough and at least on two sides and if I understood Tom, on all four sides.

Apparently the wood grain in that cant was causing the blade to do some oscillating.  Sadly, without seeing a planed board, all that we may ever have is a guess.

[Mooseherder]

The diagonal barbershop pole spiral suggests it is in the grain rather than machinery?  I didn't sleep at a Holiday Inn Express to come up with this diagnosis. ;D

[5quarter]

Tom...I confess that I have never seen that before, but I'll comment anyway.  ;) I think it is characteristic of the log and not your saw. You say this is the only instance; fine before and fine after. And the only other time you have seen it was on another Ash log. Also, I cannot envision a set of circumstances when the blade would leave 2 sets of saw marks, let alone just on that one log. Also, the pattern is identical and matches on adjacent surfaces...consistent with wood characteristics. Perhaps the log had a severe twist. Logs with severe twist often saw pretty flat. The downside is that the grain runs out of the board pretty quick. This is one of those cases where once you have eliminated every other possibility, what remains must be the truth, no matter how improbable. my 2 cents, for what it's worth. ;)

[Dodgy Loner]

I'm serious, there is no possible way that is curl or figure of any kind in the log. Look closely at the second picture. You can clearly see where the pith exits the cut. You can see oval-shaped grain lines running around the pith. And you're telling me that the "curl" runs in a perfectly 45° angle all the way through that log? Sorry, but no way. It ain't curl.

[redbeard]

Tom I can't explain the angle of tooth marks but I once had a issue with the guides that float  under the main rail that help keep the truck wheels from lifting. My guide on idle side closes to me had loosened and I noticed that wheel was not making contact with rail. It was leaving heavy rib saw marks like that. Just a thought. Have you ever relaxed your head rig and realigned it,? Its not in the manual.

[tyb525]

I'm with Dodgy and Jay, that is blade vibration. Vibrations can do really weird things, and I have seen other weird patterns like that created from vibration, especially in hard wood like ash.

[Jay C. White Cloud]

I guess after reading every thing folks are speculating on (many facts shared thus far could be part of the issue, but not all) I will restate what I have been saying, but in a different way.

I'm not guessing about my statement, I'm saying, with 99% conviction, this is "harmonic saw pattern" nothing else.  Now what can cause this aberration in the kerfing pattern, is variable to just about everything that has been described thus far, from speeds, head setup, grain pattern, etc.  It is a combination of events that leads to this anomaly, not any one event, and curly grain is not the issue with the cant in question of the OP.

[Peter Drouin]

Hi all I was cutting some w pine today and look  :D :D :D



 
Do you see the same thing I do  :D :D :D
not the best pic , but I tried :D :D

[Magicman]

Peter is the hero of the hour, and perfect timing.   

I am wondering how many of us have done it and never noticed.  I know that I have seen it for a foot or so, but I do not recall an entire cut.

[Jay C. White Cloud]

Yep, same thing, just not as severe.

[Dodgy Loner]

Good timing indeed, Peter. You did a very good job of capturing that on camera, I think it's pretty clear

[loggah]

I ve cut a lot of curly maple in my logging days and the curl never ran 45 degrees to the trunk!!! it definitely is blade harmonics ,i would say from to aggressive a feed, !!! but what do i know i use one of those round saw blades !! ;D ;D

[Tom the Sawyer]

Peter,

Wow, exactly the same pattern.    A couple of questions... did you notice any vibration?  Was it just a single log or on multiple logs?  Which blade were you using?  I notice you have an WM Lt40 and mine is a TK B-20, apparently something that can happen with either design.  I was using a WM 7°, 1.25" blade.  My pattern stayed consistent regardless of feed speed.  I think I understand how harmonic vibration could cause 'micro-dips' parallel to the blade but not how they could do it at a 45° angle.  Last question, did you resolve it and, if so, what did you do?   say_what

Redbeard,

I do tighten those pretty frequently.  Most of my work is on the road and pins that secure the head for travel go through that bracket so road shocks tend to work it loose.  I've tried adding lock washers and nylock nuts but it still loosens after a bit.  I've had it get so loose that one of the bolts fell out but it didn't cause this pattern and it wasn't tightened between logs that day.  Because of the road shock issues I check my alignment frequently.  Perhaps the combination of slight loosening and the hardness of the ash was just a bad combination that day.  I'll watch them, thanks.   smiley_clapping

[WDH]

Peter self admitted that he had a set screw loose  :D.

[5quarter]

Dodgey...someone else mentioned curl, not me. definitely not curl. but notice that Peter is cutting essentially the same log with the same result. It's the log that's causing it, not the saw. By the same token, there's nothing Tom can do with regard to his sawing to prevent it in the future. The blade is chattering in the cut as a result of a characteristic in the log. if it were harmonic resonance, that could be remedied by changing some dynamic of the saw. Just my opinion.

[tyb525]

It could also be just a quirk with that blade.

[Jay C. White Cloud]

Hey 5quarter,

I can assure it is not the log, and you are correct, it is not the saw either.  It is never any one thing, but a combination of those things.  The angle pattern of the kerfing is a give away (usually between 35° and 55°) of what is accruing.  I do not have all the elements understood yet, but can tell you that the log alone does not cause this, neither does the saw.  It's when you achieve the correct harmonic frequency among all the different elements that the patterns from.

[Peter Drouin]

Peter,

Wow, exactly the same pattern.    A couple of questions... did you notice any vibration?  Was it just a single log or on multiple logs?  Which blade were you using?  I notice you have an WM Lt40 and mine is a TK B-20, apparently something that can happen with either design.  I was using a WM 7°, 1.25" blade.  My pattern stayed consistent regardless of feed speed.  I think I understand how harmonic vibration could cause 'micro-dips' parallel to the blade but not how they could do it at a 45° angle.  Last question, did you resolve it and, if so, what did you do?   say_what

Redbeard,

I do tighten those pretty frequently.  Most of my work is on the road and pins that secure the head for travel go through that bracket so road shocks tend to work it loose.  I've tried adding lock washers and nylock nuts but it still loosens after a bit.  I've had it get so loose that one of the bolts fell out but it didn't cause this pattern and it wasn't tightened between logs that day.  Because of the road shock issues I check my alignment frequently.  Perhaps the combination of slight loosening and the hardness of the ash was just a bad combination that day.  I'll watch them, thanks.   smiley_clapping

yes on the vibration,some, I use the same blade as you 1 1/4 x55 x7 WM
I had a problem with the mill to day and had to change the blade after that log,all the lumber had the thing going on with that log
I think it;s the blade in the way it;s made, the blades are bowed when welded, to much or not enough bow, this has happen to me before , and it was a new blade   
I did resharp the blade well see  :D

[GeneWengert-WoodDoc]

I also support the idea of harmonic vibration of the blade.  (It is the same thing that causes an antenna on the car to vibrate and a specific pattern at a specific speed...the old, long antennas.)  The frequency (and therefore the vibration) can be changed by increasing the blade tension.  Also, if the blade is heating, then cooling (using a lube or even cold water) will make it stop.  Oftentimes, real fine dust will spill out of the gullets and rub the blade causing heat.  This is why a faster feed speed (if you have the power) will help or using a band blade that has a "skip tooth" will also work.  The width of the blade will change the frequency.  Also, keeping the guides as close to the log as possible will change the resonant frequency.

[5quarter]

  

[MartyParsons]

Hello,
I have seen this, I removed the blade and used a different hook angle and it went away. I think I was running a 7/34 and went to a 9/29. I  was getting lots of sawdust on the log with the 7/34 and the lines like on the picture. I had a 29 hp Kohler on a LT40 and I needed to saw faster to get ahead of the sawdust spill over.
The 9 degree solved the issue. The 9 degree has a lower tooth height and the set is lower, back angle would be 29 degree. The next log I put the 7/34 back on and the marks were gone. Different log species and smaller.
I dont think changing the mill alignment would help.
Hope this helps.
Marty

[Okrafarmer]

Some of you may have skipped right over my remark about "power hop" but I believe it is another example of harmonic imbalance. Seeing (or feeling it) in/on a 4X4 vehicle will help you understand how these kinds of things can happen on a larger scale.

Power hop is caused by the perfect storm of just the wrong tire pressure, just the wrong tread pattern, just the wrong ground surface consistency and texture, the wrong speed, poor weight distribution, and often, uneven terrain allowing one or more wheel to come off the ground at some point, along with the front and rear axle being direct coupled to each other (no mid-chassis differential or fluid coupling). The combination of all these dynamics causes the bucking bronco sensation that is known as power hop, and is experienced by ATV riders on up through articulated four-wheel drive tractors-- sometimes making a frustrated farmer have to stop and let some air out of his tires.

In aircraft, these kinds of phenomena have names like "flutter" and "compressibility"

[jackpine]

 I had never seen the type of saw marks that Tom  showed run the full length of the log before, until yesterday. White pine log that had been laying for three years on the ground, crooked and with a twist. Sawed 5 old logs before that one with only random marks but changed bands after slabbing because band was getting dull and leaving more of those marks. I had just set and sharpened some 10° bands so put a fresh one one and the marks ran the full length of the log. Pulled that band and put another on, same result. Tried more tension, less tension, more water, no water and at best got about 12" of smooth cut. Pulled that band and put a new one on, smooth  cut with only a few marks at random.

Today put one of the bands back on and cut some fresh red pine. Sawed great with no marks.

My conclusion is the same as some of those earlier, a combination of log properties and harmonics in the band coupled with the fact that the older bands have lost some of their beam strength.

[5quarter]

Hmm.

[Satamax]

Guys, i'm not a sawyer, but pretty sure i've seen this resawing wide planks with the bandsaw, with blades which had unequal set. Due to a problem of the toolsetter of the guy who sharpens my blades.

[Jay C. White Cloud]

Hi Satamax,

Sorry buddy, "tooth set" couldn't do this even if you wanted it to, the physics wouldn't work.

I use certain "hand set teeth" and "filling patterns" on both bandmill and chain saws mill to make "unusually kerfing patterns."  The challenge with any band mill, is if you your teeth are set "unequal" you can't saw a straight line because your blade will "dive" accordingly in the cut, rendery the job useless.

You could have seen it in a resawn board though; that is very possible because "harmonic kerfing patterns" can happen on any band saw blade, vertical or horizontal.  In vertical ones, tension and "push speed" are typically the solution as the blades cannot take the harmonics for long before they break or something else happens.

Regards,

jay

[Jay C. White Cloud]

Sorry, I am having troubles with my edit and load features on this laptop.  I forgot to ask if you had been doing the resawing yourself?

[frye]

 Had the exact same problem twice with some ash logs a month ago that had been cut down for 2 years.thought it was my blade! changed blade no more problems.but like what everybody else said I used the blade on another log, no problems. Thought it might have been bad set  like they say. Or the blade heats  up causing bad blade harmonics and expands and you have to retention your blade after you cut a few logs.I did find my roller guides where out of wack about 1/8" in a 6" span. Still don't know...good luck