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Author Topic: Blade flexing up in cut. Help  (Read 3535 times)

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Offline Kbeitz

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Re: Blade flexing up in cut. Help
« Reply #20 on: November 30, 2015, 08:28:03 pm »
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.
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Offline POSTONLT40HD

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Re: Blade flexing up in cut. Help
« Reply #21 on: November 30, 2015, 08:45:43 pm »
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.
I'm thinking......

Offline dustyhat

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Re: Blade flexing up in cut. Help
« Reply #22 on: November 30, 2015, 09:06:05 pm »
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.
Running a custom built stationary bandmill with a slightly modded four cyl jeep go devil engine.

Offline RPowers

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Re: Blade flexing up in cut. Help
« Reply #23 on: November 30, 2015, 10:01:41 pm »
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?
2013 Woodmizer LT28G25 (sold 2016)
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Offline POSTONLT40HD

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Re: Blade flexing up in cut. Help
« Reply #24 on: November 30, 2015, 10:51:05 pm »
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.


I'm thinking......

Offline RPowers

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Re: Blade flexing up in cut. Help
« Reply #25 on: November 30, 2015, 11:12:05 pm »
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.
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Offline POSTONLT40HD

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Re: Blade flexing up in cut. Help
« Reply #26 on: November 30, 2015, 11:35:21 pm »
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.
I'm thinking......

Offline JB Griffin

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Re: Blade flexing up in cut. Help
« Reply #27 on: November 30, 2015, 11:46:30 pm »
Its possible that your rubber spring is weak and ain't putting enough tension on the blade, not likely though.
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Offline Ox

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Re: Blade flexing up in cut. Help
« Reply #28 on: December 01, 2015, 10:28:52 am »
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.
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Re: Blade flexing up in cut. Help
« Reply #29 on: December 01, 2015, 10:51:38 am »
Ox may have a point. Blade speed could have much to do with it.
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Offline RPowers

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Re: Blade flexing up in cut. Help
« Reply #30 on: December 01, 2015, 11:34:05 pm »
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.
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Offline YellowHammer

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Re: Blade flexing up in cut. Help
« Reply #31 on: December 02, 2015, 12:38:36 am »

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

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Re: Blade flexing up in cut. Help
« Reply #32 on: December 02, 2015, 06:11:31 am »
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
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Offline xlogger

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Re: Blade flexing up in cut. Help
« Reply #33 on: December 02, 2015, 06:21:42 am »
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.
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Offline kelLOGg

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Re: Blade flexing up in cut. Help
« Reply #34 on: December 02, 2015, 07:00:11 am »
I'm going to try that, Ricky.
Bob
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Re: Blade flexing up in cut. Help
« Reply #35 on: December 02, 2015, 07:13:21 am »
You can check the blade with a razor blade to see if it needs rolling.Use a light behind the razor blade.
al glenn

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Re: Blade flexing up in cut. Help
« Reply #36 on: December 02, 2015, 07:22:09 am »
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. 
 
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Re: Blade flexing up in cut. Help
« Reply #37 on: December 02, 2015, 08:41:28 am »
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
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Offline terrifictimbersllc

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Re: Blade flexing up in cut. Help
« Reply #38 on: December 02, 2015, 09:46:09 am »
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)?
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Offline pineywoods

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Re: Blade flexing up in cut. Help
« Reply #39 on: December 02, 2015, 11:11:18 am »
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.
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