Blade flexing up in cut. Help

[RPowers]

I am having trouble with my blades bowing/flexing up in the center of wide cuts. I am using an LT28 with a 25hp engine and 4 degree WM blades. The problem is mostly in cuts 15" or wider. The lumber ends up cupped before it dries, which is very frustrating. I have made wide cuts in the past in hard woods such as post oak without the cupping, this is consistent even in wide Cherry which has always been a soft easy cut for me. I have checked the drive belt tension, its at 16#, and the rollers are both aligned. My mill has that red rubber blade tension "gauge", and I am having the problem even at significantly more tension than is recommended. Any ideas or experience with similar? Here is a pic of what I am dealing with.



 

[dgdrls]

No need to over-tension the band

How much set are you running on the teeth?
and have you had the same issue with with say a 7 Deg or 10 Deg bands

Dan

[customsawyer]

Sometimes new blades aren't right. Try a different box of blades.

[LeeB]

You might have to slow your feed speed just a tad. It's called a barrel cut, or at least that's what it's called on a vertical shop band saw. Comes from trying to make the blade eat too much at once.

[Peter Drouin]

Set on the blade is off. And a new box of blades is not always 100%. I have got a new box of blades and had to sharppen them before I use them.
Like now I get reg 7° mixed with turbo 7° in the same box. :

[bandmiller2]

RP, sharp and set are always suspect but in your case it looks like that log has a lot of tension and is cupping after the board is cut. Try a different log preferably a different species. Frank C.

[RPowers]

Thanks for the replies.

I am using ReSharp service so it is woodmizer's people in MO doing the sharp and set. I only have 4 degree right now. I think I might try some 7's next order.

I have tried feeding faster and slower and still get the "barrel cut".

FrankC, if you look at the straightedge in my picture you can see that the curve is also on the top of the cant, not just in the board.

Peter, one of my last boxes of ReSharp blades was almost unusable. It was as if they didnt grind the teeth much at all, the tips were still rounded from the previous use wearing the set corner off. Cut terrible. If the problem show's up again I'll call them, I wonder if someone just set the machine wrong.

[terrifictimbersllc]

What kind of wood is it?

If that happened on my mill I would think the blade wasn't sharp.   I cut a lot of very old timbers usually some kind of sappy pine, with 4 degree bands, and when doing so that's how I tell the blade needs changing, by putting a straightedge across the width of the cut.  Alternatively on wide hardwoods I am either using 4 or 7's.  In knotty wood it's easy to tell a dull blade by feeling over the knots.  When there's no knots, any deviation from flat detected with a straightedge, means the blade needs to be changed to cut that width of wood.

Use a 10x hand lens look at the tip of each tooth, if there is any rounding of the tips its easy to see the blade has lost its initial sharpness. If your resharp blades have any rounding of tips I would say something. Can also see by naked eye if there is any light reflecting (shiny), off the outside edge of the tooth.

[dgdrls]

terrificT   I'm interested in knowing what the set is on the bands you run,
Rpowers can you check the set on one of your bands and compare it to what TTLLC runs?

Dan

[terrifictimbersllc]

terrificT   I'm interested in knowing what the set is on the bands you run,
Rpowers can you check the set on one of your bands and compare it to what TTLLC runs?

Dan

Generally 25-26 thousandths on both 4s and 7s. I still use some 9s and the target for those is 20 thousandths, those are for sawing frozen smaller logs.   I've had no trouble with 7s set at 26 thousandths sawing frozen logs.

[drobertson]

24 to 26 as said,  automated ed is not always  locked in as some mention, they just put up with it,, resharp can be a pain, and I mean the pro's

[RPowers]

I have had this happen in everything from cherry to red oak to post oak.

I don't have any way to measure set. I've just been trusting resharp to send me properly set blades back. I put a new Resharp blade on and the problem lessened by about 50%. I am thinking they need to grind more into the profile and set them after, or I need to buy new blades.

[beenthere]

Look closely at your mill to see if either the guide rollers are reaching the teeth to remove set, or the blade going around the large wheels are not taking the set out...

[BrentRobinson]

Can you find anyone to sharpen and set locally? I find new blades are never as good as our local saw filer can get them. Absolutely no comparison. I always seem to have trouble with shipped blades pulling up or down or doing the wave and then when they come back they cut true as anything. Handle with care doesn't seem to mean much.

[bandmiller2]

As Beenthere suggested I would do a complete mill alignment according to your WM manual. Put a new band on and try it. Sometimes things happen on a band mill that defy explanation, every log is different, some resist our best efforts. Frank C.

[YellowHammer]

If this is happening routinly and consistently in many species, then I would suggest checking band alignment to see if it's parallel to the bed with the clip on alignment tool. It may be slanting up and causing the climbing, and the guide rollers are restraining it.

Uneven set will also cause this.  Or improper sharpening as well.  Use a cheap magnifying glass such as an "opticscope" found at any drugstore for about $20 and take a good hard look at the teeth.

It can also happen if sawing too slow and packing sawdust on the side of the band.  4° bands usually cut very straight, but have a tendency to pack sawdust.  If you see lots of fine flour sawdust packed on the boards, that could also be a problem. 

[RPowers]

Thank you all for the input. I will go over the mill with a complete alignment soon and see if that helps.

I haven't found any local service who will do blades, the few guys who do just do their own. Can't blame them.
RP

[Ga Mtn Man]

Contact FF member Cutting Edge about sharpening your blades. 

[RPowers]

So I took everyone's advice and checked all that I can check on the mill. I also ordered two 9 degree and two turbo 7's to try against the ReSharp 4's. I did a complete alignment on the mill, everything within 1/32", put on two new B57 belts, checked drive belt tension (at 15.5#), and threw a 14" RO butt log on along with a new ReSharp blade. Set the blade tension exactly at the edge of the washer per book spec and took a slab off. Cut was chattery and aweful, the blade climbed over 1/4" in the first 4 inches of the cut and left drag marks the whole way like I'd hit a nail. Took blade off and checked it, it had a tooth sheared off from a nail before I sent it back to Resharp, but I figured if they didn't reject it then it wouldnt mess with the cut quality when I got it back. Wrong on this one.

Put on the top blade from a new box of Resharp 4's, set the tension up a turn (middle of the washer), and cut again. The cut quality was better, but the blade still climbed 3/16" in the beginning of the cut and had over 1/16" of "barrel" across the cut.


 


 
I finished slabbing the log into a 10x9 cant, then grabbed a fresh Resharp blade and took a board off the top.
This time the rise was only 1/8" in the first two inches, still with 1/16" of cup/barrel across the board. Better, but still bad for a fresh blade on only 10" of knot-free fresh Red Oak. 
I put the 9 degree on and made a cut - less than 1/16" of rise and dead-flat across the board. Tried a Turbo 7 with the same result. I cut 3 cuts each with the 9's and 7's, and two with the Resharp 4. Consistently I had a 1/8" plus climb in the first 3" of the cut with the 4's, and the blade stayed there till the end of the cant then dropped after it exited to the original set height. Also, the cut was very slightly wavy, a 24" straight-edge showed definite high spots and low spots down the board, just under 1/16".  Both the other blades, brand new, showed a dead-flat cut against the straight-edge, but they on some cuts did rise 1/16" in the first 2" of the cut. Some cuts they didnt.

My conclusion is that there is an obvious issue with either the sharpening or setting on the 4 degree blades I just got back from Resharp. They aren't as sharp as a new blade, or at least they aren't cutting with a new blade. Maybe this is to be expected, but I assumed that a reset and grind on a factory profile would get a "factory" sharp back on them.

Since even the brand new blades  showed a tendency to rise a slight amount as well, what on my mill's alignment is causing that? Do I need more down pressure on the rollers? More tension on blade? tilt the rollers 1/16" down using the BGAT? I'm stumped.

RP

[gww]

I should let other more experiance people answer and am not trying to send you on a wild goose chase.  My homemade mill acts simular.  I always considered that it was probly a track alighment issue, maby not being level side to side in the beginning of the track where the cutting head sits.  It has been good enough for my uses that lazyness has kept me from trying to get it better.  I also used to wonder if hardness of the log ends from not cutting when felled could have some affect.  I am sure wood mizer owners will have better imput.  I would be curious of your fix if you ever narrow it down.
Good luck
gww

[Kbeitz]

I had this problem early this year. I was about ready to pull my hair out.
It turned out that my throttle got out of adjustment. I was running about
200 rpm slower than normal. It was an easy fix after I found the problem.

[POSTON WIDEHEAD]

Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.

[dustyhat]

I believe i read in in one of the magazines that cooks saw puts out about what causes this and the cure. but i could be wrong it could have been another outfit.

[RPowers]

Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.

Poston,

What blades are you running in that oak? I have found that slowing down in wide cuts will make my drive belt scream, even at 16#. Maybe these 4 degree blades pack too much dust at slow rates and bind the blade up?

[POSTON WIDEHEAD]

Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.

Poston,

What blades are you running in that oak? I have found that slowing down in wide cuts will make my drive belt scream, even at 16#. Maybe these 4 degree blades pack too much dust at slow rates and bind the blade up?

I always use a 4 degree.
My engine is always running at full throttle....29 hp.....wide open.
I just slow the head down moving the blade into the log.
Your belt should not be screaming if the throttle is wide open and your sawing slow.
My blade tension is always set at 2800-3000 PSI.
My belt tension is set at 15-18 pounds.

What is your blade tension?

Also keep this in mind. If I want a 2 inch slab for a table top, I saw my slabs at 3 inches. A thicker slab with weight on it while air drying will not cup very much if any. When the slab is dry 2 years later, I can re-saw the slab down to 2 inches. I lay my stickers 12 -16 inches apart between slabs while drying. Re-sawing is the beauty of having your own sawmill.

[RPowers]

I am running an LT-28 so there is no factory way to know what kind of tension my blade is at.... just that red rubber spring thing that you compress. I did buy a dial caliper and plan on testing the tension by measuring stretch.

After reading some articles on Cooks site I am wondering if these need to be rolled flat, as they are all on their 4-5th resharpening.

RE: resawing. This is one of the things that set me on this path of correction... I tried to resaw a large 3" white oak slab down to 2" for a customer, and every new Resharp blade I tried climbed out of the wood, even at slow speeds and way over the factory tension. My rollers were spot-on aligned too. It is frustrating and I am going to figure this out because I can't cut wavy lumber for people.

[POSTON WIDEHEAD]

Your screeching belt just sticks in my mind. It should not be doing that sawing slow.
I really think its the blade tension not being high enough.

Keep trying things.

[JB Griffin]

Its possible that your rubber spring is weak and ain't putting enough tension on the blade, not likely though.

[Ox]

Your screaming drive belt post is stuck in my head.  If this is happening during a slow cut, in my mind it means the blade is heating up and being pinched in the cut creating more friction.  Maybe try checking the set on the teeth of the blade with your new calipers.  With hardwood around .020 set works well for me.  I firmly believe too much set is better than not enough set.  A hot blade will do all sorts of crazy stuff because it is now "softer" and more able to move around.  Plus it has lost some tension which makes it do crazy things.  Maybe try some lube on the blade as well?  Diesel keeps things cool and slick and you don't use enough of it to hardly matter.  Others have different concoctions they like and works well for them, I'm simply saying what I use and works for me.  You could just use a spray bottle temporarily.  It might make a world of difference.

[LeeB]

Ox may have a point. Blade speed could have much to do with it.

[RPowers]

I tried the calipers to check deflection, and over 6" of blade I am stretching the band about 6-7 thousandths. So my tension should be plenty. I talked with Resharp, and the thought now is that the 4 degree blades I have are on their 4-6 sharpenings, so maybe we are beyond the heat treat in the tooth, and the steel is thinner or cupped or whatever allowing the band to move. The brand new blades I tried did not have this problem like the Resharps(I tried 4) did. I hate to buy new blades with almost 30 Resharp'd blades sitting there, but if these things don't straighten out I'll have to. I'm thinking of sending a handful to Cooks and having them benched or rolled to recondition the steel.

[YellowHammer]

It's odd that the resharps are not performing as advertised.

[kelLOGg]

RP,
I have experienced this "barrel" cut but never solved it. It occurs after the blade has cut for a while and maybe begins to dull a little but it occurs to soon for me to be convinced sharpness is all there is to it. A very sharp blade can cover up the need for other "adjustments" soon to show up but I have never found that smoking gun. I have also never had a band rolled and I am very curious if this would solve the problem. The FF wisdom is that only steel wheels (like mine) require rolling but Tim says all bands need it (and has told me of accounts where all he did was roll a band and it cut straight). If you have it rolled I would be very interested in the outcome. Hang in there,
Bob

[xlogger]

I was told once that if you turned the blade inside out and put it on the mill and ran it for a few minutes it would do the same as band rolling it, of course don't cut any wood while doing this.

[kelLOGg]

I'm going to try that, Ricky.
Bob

[slider]

You can check the blade with a razor blade to see if it needs rolling.Use a light behind the razor blade.

[Solomon]

I've been using Munkfor blades from Kenna-Saw since I first got my LM-4 over eight years ago.
They are 229 inches x 1 1/2 x 7/8 with a 10 or 12 degree pitch.
I buy 50 or more at a time for $27.00 each drop shipped to my front door.
Other than hitting a foriegn object or a very hard knot, I've had no issues with the blade rising and diving in the cut.
Theese are new blades out of the box and the ones I set and sharpen seem to work just as well and leave a very nice finish on the board.
Assuming your mill is in proper working order, perhaps you should give them a call.
Great blades a a really decent price. 
 

[kelLOGg]

You can check the blade with a razor blade to see if it needs rolling.Use a light behind the razor blade.

I've seen new blades right out of the box show the arc of light under the razor.  :-\ :P
Bob

[terrifictimbersllc]

Wouldn't a thousandth or two in band cup, if it is there, be of no consequence , in light of all the tooth set (25 thousandths on each side for example)?

[pineywoods]

A head scratcher problem. I had a similar problem, what I found may shed some light on the situation. I sharpen and set my own, so no outside influences. Sawing some syp 1X12 and got into a bunch of embedded rocks, dulled the blade a bunch, so tossed in the "to be sharpened " pile and went on sawing. Later cleaned up the blade, set and sharpened. Put it back on the mill to edge some 4/4 stuff and got the worst case of dips and dives I have ever seen. Must be the re-sharp  : , so set and sharpen again. Same thing, other blades saw just fine. The logical thing to do would be to toss the blade and forget about it, but that just ain't my nature.
A bit of comparison with a good straight edge shows the blade between the guide rollers to be bowed outward slightly, ie the tooth edge of the blade is just a bit longer than the back edge, likely stretched from sawing through marble sized rocks. A little pressure against the wood, and the blade will twist either up or down depending on other forces. No logical way to shrink the tooth side, but can stretch the back side to match. Rolling will do exactly that, but I don't have that capability, so..lay the blade on a flat metal surface (anvil) and hammer the back 1/4 inch or so every inch, all the way around the blade. This will stretch the back edge just a tiny bit.
In retrospect....I see numerous references on the forum to the need for rolling band blades to take out cup, especially with cooks blades and mills. I run woodmizer blades and equipment, never saw any need for it. What escaped me is that for a blade to cup, the center of the blade will be a bit longer than the edges. Exactly what you would see with crowned metal wheels and to a lesser extent with belted wheels running crowned belts. If the stretch is a bit off-centered (likely after a few sharpenings) the result is a crooked blade. Now from a practical standpoint, blades will probably break from repeated flexing before this becomes a problem, BUT mr. Murphy is well acquainted with sawmills.

[customsawyer]

When you check a blade for flatness sometimes you have to check it while it is on the mill. If your blade is cupped a few thousandths of a inch it will make your blade cut that much more on one side and that much less on the other. Combined you can be looking at a difference .005-.010 from side to side and this will make your blade dive, climb or crown.  The flatter your blade is the flatter your lumber will be.
In this particular case I think the OP is possibly looking at a different issue. If his belt is squealing while he is going slow there is a good chance that the set is so far out that the blade is binding in the cut. If he wasn't going slow he would likely stall his engine.   

[Kbeitz]

So.... If your blade is cupped a few thousandths of a inch you could make up for it by setting the teeth on the other side to make up fpr it... Right ?

[terrifictimbersllc]

In quite a few yrs now of paying attention to band sharpening, I've never seen any discussion from WM about band flatness, and they don't sell a roller. 

[SawyerBrown]

OK, just a couple of thoughts, since my LT35 is running the same engine and blade tension red-rubber-compression-thingy ...

I too have cut a considerable amount of wide oak (and other hardwood) boards without this happening.  But I've never had drive belt squeal, not even close -- the engine will lug long before the belt starts to slip.  So if the engine isn't lugging but the belt is slipping, the blade may be slowing down considerably.  Have no idea whether that explains anything, but could imagine that would move a lot less sawdust for every length of travel.  Same idea as engine speed too slow as was mentioned earlier.  If it's still happening, I'd re-check belt tension.

I've never had to over-tension the blade to get it to cut straight.  Personally I don't think that's the issue, at least with our size machine.

If the blade is taking an immediate climb regardless of which blade you use (new vs ReSharp, other variables), that seems to me to indicate guides pointing the blade up-hill.  But I assume you checked all that if you went through  the whole maintenance sequence ...??

Finally, I've had some issues with ReSharp blades of late, but not as you're describing.  I'll get a scratch mark from tooth/teeth offset problem as soon as I take them out of the box (see photos), but the blades seem relatively sharp (but maybe not as sharp as new??), and still cut straight.  New blades don't do this at all.  So I wouldn't rule out other ReSharp problems.  (Note: in WM's defense, they have checked blades that I've tagged, agreed there was a problem, and not charged me for re-sharpening ... still a great company!)


  

 

[Magicman]

The above indicates a tooth missing or a tooth with very little set.

[customsawyer]

So.... If your blade is cupped a few thousandths of a inch you could make up for it by setting the teeth on the other side to make up fpr it... Right ?

Wrong due to the fact that the blade isn't going to run consistently on the blade guide rollers.

[JB Griffin]

My best guess is either engine speed too low or drive belt and or drive pullys glazed over and not gripping like they ought to.

[Jim_Rogers]

I thought I read somewhere that when a blade rides up it's called "log push off."
and that most of the time that it happened it was because of a dull blade.
If this is happening with every blade put on then it must be the sawmill and not the blade(s).
Cutting slow and hearing the belt squeal means it is slipping. Belts should not slip. The belt tension is not right, if it squeals, in my opinion. If it is slipping then the blade is not traveling at the correct speed to do it job correctly. This could be the cause, or at least contribute to the cause.

I have had the blade ride up. Changing to a sharp blade has always solved that problem for me.

Blade tension is important as well. A clean blade that is not rubbing either the log or the board is important too. A rubbing blade gets hotter. A hotter blade gets longer and thereby looses tension. With dial indicators we see that when the pointer goes down.
If you don't have a dial indicator then you have to increase the blade tension if you feel the blade and it is hot/warmer then normal.
If it is rubbing the log or the board then it could be a sign of not enough set to remove the wood so it doesn't rub.

I'm sorry but I don't endorse using diesel to keep a blade clean. The mill manufacturer says use water to keep your blade clean. Build up on the blade makes it fatter and then it can rub the log or the board and get hotter. When I see my blade getting hot (my dial indicator goes down) I increase the water lube flow to keep my blade clean and cool, so it cuts straight as it can.

Jim Rogers

Hopefully you'll find the solution soon.

[Magicman]

Thank you Jim for a well thought out reply.   

[sawdusty1]

Could bad bandwheel bearings with too much play cause this?

[RPowers]

Alright, I have been gone a couple days and my thread got ahead of me!

First, thank you all for the ideas, insight, and suggestions. I sawed some hickory and black gum for a customer two days ago and the mill cut alright using the Resharp 4 degree blades. Got a few very small waves around knots in the hickory but that is not unexpected with my mill in a 14" cut of hickory.  I am still getting a visible rise on entry and a little crown, but at this point it is not so much that i can't mill with them. Still more than I want, and I do think the fact that the blades are getting old has something to do with it. I will check the back of the blade with a straightedge while it is tensioned on the mill and see what that tells me, along with checking for a cup across the band.

After my first complete head and deck alignment(which I used s Resharp blade for) I went back with a brand new 9* blade which had never been used and realigned the entire head using that new blade as my reference, just in case. The old blades still rise and cup in the cut. I have my blade tension over factory, and my drive belt slightly over. The drive belt only slips occasionally, and in a wide, hard cut like 20+ inches of oak. Interestingly it is often when I slow down around a knot or something, but grabs again if I speed the cut up (manual feed mill). Until this recent issue with cupping which started this summer and has gotten worse, I have always been able to switch blades at the first sign of trouble and that solves any problem. I don't doubt that the was a very slight alignment issue, but I check my blade and head frequently so things usually get fixed. Now "sharp" blades and an aligned head isnt fixing the issue. My bandwheel bearings seem tight and smooth. I am going to replace the drive belt and order a new handful of 4* blades for comparison. Might even try some regular 7's along with the 2 turbos I've got to try. Hopefully a couple weeks of experimenting will give me some insight.

Thanks again to all,
Ryan

[Ox]

What a frustrating problem.  :-\

[dustyhat]

Had your same problem today. but it was my fault. started to back up to cut off a not and the blade poped of getting a little twist in it .put it back on and every cut looked like i was cutting barrel staves. could have been the set or the twist but it was there. changed the blade out and it went away. so alignment wasent the prob for me just a messed up blade. might give you something to go by. just trying to help.

[LeeB]

I truly believe that band speed is the issue. Whether it's due to a slipping belt or not enough engine speed, if the blade cant cut fast enough it's going to deflect backwards as you try to push it through the log. This will cause it to roll the front of the blade towrd the back. The guides are holding it straight at the edges of the cut so you end up with a barrel cut.