Blade Jumping in first 6" of Cut

[quadracutter222]

Hi all.  Wondering if anyone can shed any light on an issue I have noticed.  I can think of three potential causes but wanted to ask here also.

The mill runs 2" Lenox 1" spacing blades and with a new blade, seems to rise up in the first few inches of the cut before leveling out.

One potential cause could be entry speed.  Too fast might be loading the blade backward, which causes it to spring back forward when fully in the cut causing the blade to raise.  This was cutting second-growth douglas fir.

Another issue could be from the blade guide adjustment.  My mill had pads that put downward pressure on the blade only, nothing like a roller or bearing to prevent it from going backward.  Perhaps this is a blade tension issue or too much deflection ie guide blocks too tight.

It was also pointed out that the adjustment in the idle side wheel has too much slopp and needs to be reshimed and adjusted back to square.

I am putting this in the "I'm learning" category, and its likely something I need to practice on or learn how to adjust properly.  

Any input would be great!  I can add specific pictures if that would be helpful

Cheers, 

[BenTN]

Maybe entry speed too fast and band speed is slowing drastically? I will enter a cut slow and raise the feed speed once the blade is inside the cut.

[Lawg Dawg]

Maybe check drivebelt tension?

[YellowHammer]

Typically a rise in the cut and return to neutral indicates an inability for the band to take the initial sawing load, but then recovers some lacking property (that is the question, what?) and saws normally.  

In my experience, the characteristic band's return to neutral and straight cutting means the alignment is fine, the band is fine and the issue is something transient. 

So in my mill it is usually caused by a temporary over feed at the beginning of the cut caused by loose drive belt tension.  It can also be caused by the band getting pushed out of alignment temporarily by the the initial impact, maybe caused by worn guides or bearings, inadequate down pressure, bandwheel crown, bandwheel belts, etc.  Its something transient, so look for that sort of thing.  

Sometimes it can be caused by the grain of a particular log, but if it's consistent, the problem is with the mill.  

Remember that a property adjusted resaw doesn't slow down on entry, and a sawmill shouldn't have to either, except for the motor to accept the sawing load, which basically results in an overfeed condition.     

[highleadtimber16]

I saw a lot of Fir. You need to have proper tension on your drive belt to keep that blade level. Definitely have a look at your belt.

[quadracutter222]

I went out and inspected the cant and the jump is only on two parallel sides.  And it was mistakenly sawn from the big end too.

I will look out for the above issues as I run more logs.

[ladylake]

 Try less hook angle in frozen wood. Steve

[Remle]

I went out and inspected the cant and the jump is only on two parallel sides.  And it was mistakenly sawn from the big end too.

I will look out for the above issues as I run more logs.

It's personal preference as to which end to saw from. But i always to saw from the big end of but logs that have a large swell and down from the top on other logs with large branches. My reasoning is, a less than super sharp blade will follow the grain of the wood along these areas causing the blade to follow the curve and rise up as the grain does, which is contrary to what you describe.. Cutting from the back side of the grain in these areas the blade is at a better attack angle to the slope of the grain and less likely to follow the slope. Again it's a matter of preference and others do not agree that it makes any difference, it's just my preference .

[dgdrls]

Try less hook angle in frozen wood. Steve

2nd the suggestion
D

[JB Griffin]

Does it leave a hump? Ie ride up and back down or does ot rode up and stay?

Take at good look at mill alignment and trash those lennox blades, get some 4 or 7deg blades depending on the hp of your mill.

[quadracutter222]

Does it leave a hump? Ie ride up and back down or does ot rode up and stay?

Take at good look at mill alignment and trash those lennox blades, get some 4 or 7deg blades depending on the hp of your mill.

Thanks!  It was a hump, up a bit in the first 6-8 inches then back down.  I bucked the dried hard ends off, re-aligned the blade guides, that with slow entry fixed the issue.
What pitch can you recommend for sawing douglas fir?  Power on the mill is Kohler 25hp

[redbeard]

Sounds like it's the log giving you the issue if your trying too enter the big end on a butt log you could be fighting tension, in the log, if there is wide rings on one side and tight rings on the other  your going to have some possible issues. 7° blades work best on Doug fir, Also enter the small end when sawing Doug fir, it's actually very hard on all band blades they don't last as long like sawing cedar , Alder , maple and the other white wood firs.
You guys in BC have the nicest Doug fir there is and Giants too boot!

[Tin Horse]

My buddies Lt 40 wide was doing the exact same thing. It still did it with a brand new 7 degree WM carbide. We were cutting a hard maple 36" and frozen. We ended up tensioning  up the band and real slow through the cut. Worked great.

[JB Griffin]

Does it leave a hump? Ie ride up and back down or does ot rode up and stay?

Take at good look at mill alignment and trash those lennox blades, get some 4 or 7deg blades depending on the hp of your mill.

Thanks!  It was a hump, up a bit in the first 6-8 inches then back down.  I bucked the dried hard ends off, re-aligned the blade guides, that with slow entry fixed the issue.
What pitch can you recommend for sawing douglas fir?  Power on the mill is Kohler 25hp

1 1/4"x.045" 7/8" tooth spacing Kasco 4deg. You don't have the hp to even begin to justify 2" blades.

[quadracutter222]

Does it leave a hump? Ie ride up and back down or does ot rode up and stay?

Take at good look at mill alignment and trash those lennox blades, get some 4 or 7deg blades depending on the hp of your mill.

Thanks!  It was a hump, up a bit in the first 6-8 inches then back down.  I bucked the dried hard ends off, re-aligned the blade guides, that with slow entry fixed the issue.
What pitch can you recommend for sawing douglas fir?  Power on the mill is Kohler 25hp

1 1/4"x.045" 7/8" tooth spacing Kasco 4deg. You don't have the hp to even begin to justify 2" blades.

Thanks JB, I have nothing to fall back on besides what the previous owner passed on.  Do you know of any references I can go to, to look this sort of thing up?  If there is something different or better I am not set in stone for sure.  I suppose a call around to mill manufacturers would be worthwhile.

[Will_Johnson]

If the logs have been down a while the ends will dry out, making them harder. This means the feed speed both on entry and exit needs to be slower. Often if logs have been down and the ends have checked, the easiest thing to do is just cut off the ends.

[JB Griffin]

What causes a hump at the start is...1 feeding to fast, 2 dull blade, 3 incorrect or uneven set, 4 incorrect hook angle, 5 misaligned mill and or guides. 

Lets break this down a little bit. 
1. Feeding to fast.  Pretty straight forward,  but has many variables. Feed speed is dependent on blade condition,  width of cut, species of wood, condition of the log(old and dry or fresh and juicy).

2. Dull blades don't cut good
3. Set has to be consistent and even side to side. 
4. Incorrect hook angle. Hook angle depends on hp ( actually torque) of mill. And to a lesser extent species of log. Lower hp mills require a lower hook angle. Less than 25hp 4deg,  25hp+ might could run a std 7deg and maybe not. 30hp 7deg range here. 35hp+ deep gullet 7deg (wm turbo7, kasco 7/40 supermaxx). 
Species of wood plays a part here too. Harder (or frozen) wood require a lesser hook angle. For example,  at work I run a Baker Dominator 50hp 3phase, it has more available power than most every other mill in its class. Cutting red oak I use one of the deep gullet 7deg blade listed above, but, in white oak those same blades fall on their face. Reprofile to a deep gullet 4deg and they will perform. 
5. Guide alignment.  The blade must be parallel to the deck, and stay there through its entire range of motion.

Hope that helps a little.

[ladylake]

 
  I find 10° blades will leave a hump in frozen wood soon as they get even a little dull, 4° will cut straight until they are real dull.   Steve

[Cutting Edge]

quadracutter222,

x2 on Blade width & HP as JB Griffin already stated.  There's no way 25hp has enough sand in it's britches to pull a 2" wide blade. 

You'll be much better 1-1/4", .045, 4 deg.  Depending on the blade speed, you might get along with a 7 deg in smaller logs


I'm gonna throw another wrench in your troubleshooting....

"Another issue could be from the blade guide adjustment.  My mill had pads that put downward pressure on the blade only, nothing like a roller or bearing to prevent it from going backward."

I am assuming your mill uses phenolic (or similar) blocks as your guides?  If so.....

 - 1)  Those blocks REQUIRE dressing to square them up from time to time.  Production machines require it twice a day.  You can align it until you're sick, but unless they are dressed/squared up, it will do little to help.

 - 2)  If you don't know already, you also need to run deisel, or similar oil base substance.  Water/soap will only accelerate the wear on the guides.


You stated there is no backup bearing or pad to prevent the blade from deflecting rearward while in the cut ??

 - Can you post a couple pictures of your guide system??  This may help clear up alot of unknowns.


Hope this helps get you pointed in the right direction. 

[quadracutter222]

quadracutter222,

x2 on Blade width & HP as JB Griffin already stated.  There's no way 25hp has enough sand in it's britches to pull a 2" wide blade.  

You'll be much better 1-1/4", .045, 4 deg.  Depending on the blade speed, you might get along with a 7 deg in smaller logs


I'm gonna throw another wrench in your troubleshooting....

"Another issue could be from the blade guide adjustment.  My mill had pads that put downward pressure on the blade only, nothing like a roller or bearing to prevent it from going backward."

I am assuming your mill uses phenolic (or similar) blocks as your guides?  If so.....

- 1)  Those blocks REQUIRE dressing to square them up from time to time.  Production machines require it twice a day.  You can align it until you're sick, but unless they are dressed/squared up, it will do little to help.

- 2)  If you don't know already, you also need to run deisel, or similar oil base substance.  Water/soap will only accelerate the wear on the guides.


You stated there is no backup bearing or pad to prevent the blade from deflecting rearward while in the cut ??

- Can you post a couple pictures of your guide system??  This may help clear up alot of unknowns.


Hope this helps get you pointed in the right direction.

Thank you for the information.  Is there a correlation between wheel thickness and what band should be used?  The previous owner did a fair bit of testing and landed on these blades as best, but I am willing to try smaller blades if those work better for the HP and wheel thickness.  
Yes those are the type of guides I have (but do have Cooks rollers on the way).  I will post some pictures and look at their squareness.

[quadracutter222]

After a bunch of research, the advice here, calling WoodMizer, Cooks and the outfit I get blades from, I will be switching to 1 1/2" blades to correspond with the 1 1 1/4" thick 24" wheels.  Wheaton Industrial Saw was nice enough to take the new 2" blades on commission so I'm not stuck with both.

As for the guides, here are some pictures.  Both as installed and showing out of square.  Dressing will happen tomorrow.  Hopefully, these can get me through 2-3 weeks until the Cooks rollers come.  

[Cutting Edge]

As for the guides, here are some pictures.  Both as installed and showing out of square.  Dressing will happen tomorrow.  Hopefully, these can get me through 2-3 weeks until the Cooks rollers come.  

WOW, I'm surprised you were able to saw anything with much consistency with what you currently have. 


Upgrading to a roller guide system will be the BEST improvement you can make.  Converted several mills for customers, and NONE have regretted it.  


Regarding your steel wheels... If you're having problems maintaining tracking, the wheels are probably LONG overdue to be re-crowned.


1-1/2" blades will help, but because of your HP/torque, you still outta seriously consider running a lower hook angle. 


Sounds like you're headed in a positive direction !!    Be patient, there are bound to be other little issues arise you'll have to work through.

[quadracutter222]

As for the guides, here are some pictures.  Both as installed and showing out of square.  Dressing will happen tomorrow.  Hopefully, these can get me through 2-3 weeks until the Cooks rollers come.  

WOW, I'm surprised you were able to saw anything with much consistency with what you currently have.  


Upgrading to a roller guide system will be the BEST improvement you can make.  Converted several mills for customers, and NONE have regretted it.  


Regarding your steel wheels... If you're having problems maintaining tracking, the wheels are probably LONG overdue to be re-crowned.


1-1/2" blades will help, but because of your HP/torque, you still outta seriously consider running a lower hook angle.  


Sounds like you're headed in a positive direction !!    Be patient, there are bound to be other little issues arise you'll have to work through.

Thanks!  Do you know much about dressing those guides?  Should the angle be maintained, just dressed square or should I dress the whole block square and flat?  Angle can be seen best in the second picture.
Wheel tracking was an issue before I learned how to adjust the idle side components.  Tracks good now, just with the 2" bands there was a ton of back or front overhang.  
On the hook angle, can you elaborate more?  The cutting I will be doing is softwoods.  Both the woodmizer rep on Vancouver Island and the blade folks said to start at 10 degrees for that hp.  Enough information to make a persons head spin!!!!

[Cutting Edge]

"Should the angle be maintained, just dressed square or should I dress the whole block square and flat?" 

You need a dead flat/square surface.  Best to square it with the fixture as it gives reference surface for checking wear.  Unless you've got work coming, personally, I wouldn't spend the time and wait for the roller guides.


"Wheel tracking was an issue before I learned how to adjust the idle side components.  Tracks good now, just with the 2" bands there was a ton of back or front overhang."

Keep an eye on tracking as this will be your first clue if the crown has degraded and needs machined.

"On the hook angle, can you elaborate more?  The cutting I will be doing is softwoods.  Both the woodmizer rep on Vancouver Island and the blade folks said to start at 10 degrees for that hp.  Enough information to make a persons head spin!!!!"

Running a 1-1/2" blade is already going to take away some power in comparison to a 1-1/4".  You will notice a huge gain dropping back from 2".  I'd recommend going no heavier than .050" thick

25HP pulling 1-1/2", .050" blade AND any parasitic draw (hydraulic pump, alternator, etc.) eats away at the sustainable torque the engine can maintain, BEFORE it starts sawing.  Depending on what the engine is running, you could already be down to/below 20hp.

I have never sawed Doug Fir, but maybe it is similar to Virginia Pine ? (sawed PLENTY of it)  V. Pine is very soft, but the knots are hard like glass.  Sound like you're hitting nails when cutting through 'em.  Wouldn't even attempt with a 10 deg. (farthest from "all purpose" on 25hp), a fresh 7 will handle it "OK" until it just begins to dull then the waves will start at the knots... engine can't feed/density change and blade slows down. 

A 4 deg, even when nearing "dull" and ready to change will still handle the knots MUCH better than a more aggressive blade... it's taking a smaller bite... easier on the engine to maintain speed.  As for feed rate running 4 deg, should be close to a 10 deg (possibly better), BUT, your lumber will be MUCH better throughout the time that blade is running. 

Hope this makes sense to ya.

[quadracutter222]

Thanks for the continued help.  Makes sense for sure.  What was recommended was 0.045" for thickness.

As for the width, can and 1 1/4" blade run on a 1 1/4" steel wheel?