LT40 cutting problems!

[RWTF]

Hi, I will cut a very long story short. Breifly, I run a woodmizer LT40 ('98), cutting mainly Douglas fir, oak and other pacific coast softwoods that we now grow in the UK. Over the last year I have noticed that cutting large DF with B475 blades, the board is crowned (the middle of the board is sometimes 1/2 inch higher than the outsides). Initially I checked blade guide tilt, then I took the blade guides off and checked the tilt of the drive wheels but all was fine. The first few cuts are great but after that it seems that the edge goes and it starts to struggle and crowns. I have a de-barker and the logs are fairly clean.... Is DF very abrasive? are my blades dulling too quickly and crowning is a product of a dull blade? So why are my blades dulling so quickly?
Would appreciate any thoughts on my problem.....
Thanks, Rupert.

[southpaw]

Are you lubing the blade while cutting?

[RWTF]

Gravity fed water, no lube mizer

[beenthere]

Are the teeth contacting the guide wheels and causing them to lose their edge?

[RWTF]

No, blade guides are adjusted correctly. Deflection is as recommended, tooth set is equal both sides...

[Bodger]

this is a longshot but try running the blade in the evening and see if it is producing any sparks...I fought with a similar problem and finally found the blade was contacting the blade guard causing the problem.

[zopi]

Blade tension staying constant?

[Tom]

That is a pretty common malady and can usually be traced to too-much-rake and/or too little set.  It doesn't mean that the band is bad, just that it doesn't match the application.  Having wood harder than you are used to sawing might be the problem(frozen wood?)._  Decreasing the rake can help. increasing the set might help.

[woodmills1]

new blades, or resharp,  if resharp, yours or someone else.  My own resharp often crown the middle of wide because I am lazy on setting.

[Brucer]

Is DF very abrasive? are my blades dulling too quickly and crowning is a product of a dull blade? So why are my blades dulling so quickly?

99% of my sawing is in Douglas-Fir, and no, it isn't abrasive. I have had the crowning affect once in a while and it is always one of three things: 1) more set on the inside of the band than the outside; 2) outside teeth getting dull more quickly than the inside teeth; 3) A frozen log, sawing toward the butt end.

Since your first few cuts are straight, that would tend to rule out #1, unless something is affecting the set after you start cutting. I can't think what would do that, but it's worth checking the set on an offending blade after it starts giving trouble.

I would look at #2. D-Fir bark can hold a lot of dirt in the fissures. If your debarker is set just a little high, the outside teeth can dull faster. I've also had problems sawing in snow and ice. Ice can keep your debarker from penetrating into the bark. In very cold weather I've also had sparks flying off the exit side of the cut when dirt gets frozen into the bark.

If the teeth are getting uniformly dull, the blade will usually wander, giving you a ripple rather than a crown. However, I've had a dull blade start to crown in the butt end of a very wide cut.

I'm sawing with Wood-Mizer blades, .045, 1-1/4, 10 degree tooth angle, with a 0.023 set.

[ladylake]

Try less hook.  Steve

[LOGDOG]

RWTF,

   Do you have a WoodMizer blade with a 4 degree hook angle available? I'd just about bet if you put one on your mill with everything else being aligned properly it would cut straight as an arrow. In frozen or otherwise tough woods lower the hook angle like Tom said -although I think he used the term "rake". Also, the bigger the logs the more you need to increase your set. Since discovering the value of a low degree hook angle I haven't had any trouble with wavy boards.


LOGDOG

[Bibbyman]

this is a longshot but try running the blade in the evening and see if it is producing any sparks...I fought with a similar problem and finally found the blade was contacting the blade guard causing the problem.

I've had a simular problem -  I found that the blade was hitting on the guide arm guide. 

I'll also suggest you check your drive V belt conditioni to see if they are worn so low as to let the blade ride on the pulley rim.  This will press the set out of the "inside" teeth. 

Check your blade tracking too to see if your not running it too far back.  Thus could cause the same condition.

Good luck.

[LOGDOG]

RWTF,

   Check out this link to the troubleshooting page of Suffolk Machinery Corp and Timber Wolf Blades.

http://www.suffolkmachinery.com/troubleshooting.asp

   Notice the first two symptoms and solutions. #2 particularly sounds like yours. Quote: "BLADE RIDES UP IN THE CUT - plus when you pull the board off you have a bow in the board. This is caused by too much hook angle and not enough set. Reduce the hook angle by 2 degrees and increase the set by .003" per side."

Even if everything else is right, if your blade is set up wrong you won't get the performance out of your mill that you need. A fresh razor sharp blade might make a couple good passes, but when that "razor edge" isn't there anymore the overall setup of the blade will be manifested.

That's my best guess. Check out the link. May even want to print all that out and keep it in your owners manual. I did.

LOGDOG

   

[ladylake]

Right   If your running 10* hook decrease by 6* . 4* blades cut straighter in tough and frozen wood. Be carefull not to get too much set in frozen wood, that leaves more sawdust on the log which  will freeze hard and cause trouble.   Steve

[Bibbyman]

If all the above advice don't seem to help,  suspect the tension and condition of the main drive belt. 

It may have enough traction to not slip when the blade is very sharp but when it starts to dull,  the belt will slip and thus lower you blade speed.  As the blade speed lowers, sawing energy is reduced and it all goes downhill from there.

[RWTF]

Thanks you lot, will see what happens. The hook angle and the set sound like they need attention. Will take a few days, but I'll let you know. What a wealth of knowledge... Cheers.

[woodmills1]

I ran into the operator of woodmizer maine last weekend at a hunting and fishing show in Salem NH.  Among the many talks and shared events we hashed, he told me in his colder, even than me, climate a 1.5 inch blade will kinda float on frozen logs due to the longer unsharpened part.  He said all the woodmizer owners he knows switch to 1.25 blades for the cold.............. :P

[Coalsmoke]

Hi, I will cut a very long story short. Breifly, I run a woodmizer LT40 ('98), cutting mainly Douglas fir, oak and other pacific coast softwoods that we now grow in the UK. Over the last year I have noticed that cutting large DF with B475 blades, the board is crowned (the middle of the board is sometimes 1/2 inch higher than the outsides). Initially I checked blade guide tilt, then I took the blade guides off and checked the tilt of the drive wheels but all was fine. The first few cuts are great but after that it seems that the edge goes and it starts to struggle and crowns. I have a de-barker and the logs are fairly clean.... Is DF very abrasive? are my blades dulling too quickly and crowning is a product of a dull blade? So why are my blades dulling so quickly?
Would appreciate any thoughts on my problem.....
Thanks, Rupert.

Have you put a new blade on yet to see if it does it with a new out of box blade? I have had this problem too, set problem caused blade to stretch and cut a crown. Wasn't a problem until I reset and resharpened a few times.

[kderby]

Good answers! 8) 8) 8) 8)

Brucer gets extra points for considering the dynamic of the grain at the butt end of the log. 

I never get to mill hardwoods.  When I mill large pine or fir, sometimes there is internal tension in the butt.  It may be obvious as a visible twist in the grain or it may not show up until the the cut is made.  I wonder if hardwoods do this as well.

I get better recovery and better lumber when I cut from the top to the bottom of the log.  I wonder if the large mills notice that as well.

Thanks for question RWTF and thanks all for the answers.  I learned!

[Brucer]

Brucer gets extra points for considering the dynamic of the grain at the butt end of the log. 

It weren't so much considering as an unhappy experience. A few years back I was sawing some WRC in January for a special order. The logs were trees two weeks before. Everything was going well until we got a really cold day, then the blade started curving at the butt end of the log. I cursed the blade, got a brand new one out of the box, and tried again. After 4 new blades I started to think it might be something else ???. I finally figured it out -- now that I know what it is, I can spot it when it's happening.

[customsawyer]

I can't speak for any of the other big mills but the hardwood mill that I do most of my cutting for always works from the butt end of the log and I do as well with the LT70. You do get a log now and then that has what I like to call stress in its butt that will make a blade rise as it enters the log but by turning the log a little bit more it will seem to help.