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a common band blade problem?

Started by paul case, May 10, 2011, 10:50:54 PM

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paul case

i have noticed on the 2nd or 3rd sharpening on some brands of blades have made the blade rise in the first 6 inches of cut and it falls off the end of the log as much as 1/8'' it was the same on every cut, every log. i thought it was just my sharpening or setting, but i checked the tracking on the mill and the guides. no slack and everything seems to be dead on.
i tried a different brand of blade and i can sharpen them till they are dead and they cut straight all the way with the same sharpening and setting. i talked to a friend of mine who saws with an wm lt40 and he has the same trouble wth the same blades and even with some others. the bad acting blades seem harder  and are about $8 a blade more expensive.
anyone else notice these problems?
what is the fix?
pc
life is too short to be too serious. (some idiot)
2013 LT40SHE25 and Riehl edger,  WM 94 LT40 hd E15. Cut my sawing ''teeth'' on an EZ Boardwalk
sawing oak.hickory,ERC,walnut and almost anything else that shows up.
Don't get phylosophical with me. you will loose me for sure.
pc

Brian_Rhoad

Check the hook angle of the teeth. A higher hook angle, 10* verses 8*, will make the blade rise in the log when sawing hard woods such as Oak and Hickory. The log will be crowned across the face of the cut also. 2 degrees in hook angle will make a difference.

tyb525

I have that problem also, it's discouraging to me. I don't really know the cause yet. I am using the same grinder you are. I'm assuming I'm using the same brand as you. I haven't tried any others yet.
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!

Tom

Yes, hook is a reason, but so is tooth height.  It's a syndrome called "push-off" and can happen when the gullet fills too quickly.  That's why a lot of people experience it after a couple of sharpenings when the gullet isn't ground deep enough and the tooth height suffers.


tommone

Tom,do you think the push-off effect  can be caused by uncorrected grinding wheel wear?

ely

i have seen that before but couldnt tell you what blades were doing it.

try slowing your feed down with the suspect blade, if its filling the gullet and causing it  the slower speed should produce the right cut.

im not saying to do that as a practice, just to see if thats the problem.

paul case

ely,
i have tried that too. my mill manufacturer said that i may need to run the band tighter as i sharpen it but that dont seem to help either. even just on a 4'' cut you can see it on the board and as the band exits the log.
tom and brian may be on to something.
the hook angle is remaining the same on them. i am sure of this since i have the cbn wheel on the grinder and it doesnt seem to wear off at all. i also have set my sharpeners hook angle with a new band. it hasnt moved.
the gullet shape on the ''bad acting'' bands does change. new ones have a deeper pan in between the teeth when new. as i sharpen them this flattens out some. the cheaper ''straight cutting bands'' have a flatter bottom in the gullet.
if you want to talk brands pm me. i will not post any of the brands here because this is obviously related to my sharpening. the brands of all the kinds of blades i have used are all sponsors here and i dont want to discourage anyone from trying their products. i do appreciate all of those sponsors and i can recomend all  of the ones i have dealt with. fast, reasonable service and good products. thanks youall.  pc
life is too short to be too serious. (some idiot)
2013 LT40SHE25 and Riehl edger,  WM 94 LT40 hd E15. Cut my sawing ''teeth'' on an EZ Boardwalk
sawing oak.hickory,ERC,walnut and almost anything else that shows up.
Don't get phylosophical with me. you will loose me for sure.
pc

ely

paul, here is something that ive not seen mentioned here, and it may or may not have relevance to the problem, but in the past i let the spring tension that holds pressure on the sides of the band while it goes around the sharpener get loose. i didnt realize this and when the rock would come down on the face of the tooth it was pulling the band up off the bearings as it was grinding. effectively changing the the hook angle to who knows what... those bands would give me fits and for a week or so i thought i could not sharpen bands.

i finally figgered this out and everything jumped back to normal.

pineywoods

Paul, I have experienced the same problem and it about drove me nuts before I found it. In my case it was a sharpener problem. Try this. Mount a blade in the sharpener, clamp it down, but leave the grinder turned off. Then grab the blade and try to pull it forward, if you can, you have found the problem. I dis-assembled the clamp mechanism and found a lot of crud built up between the pieces below where the blade slides through. Crud kept the clamp from holding the blade in position while it was being ground. Also sometimes when the pusher arm retracts it would catch on the top of a tooth and pull the blade slightly backwards. On mine, the part of the pusher arm that rides on top of the blade is a roll pin. A notch had worn in the bottom side, catching on the tip of the tooth.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

Tom

Quotedo you think the push-off effect  can be caused by uncorrected grinding wheel wear?

Uncorrected grinding-wheel wear could cause a myriad of problems.

I can see how the tooth height, gullet shape, tooth back and transition area at the base of the tooth could all be effected.  Rake, or hook, is usually a result of the positioning of the stone, not the wear.

As was mentioned by Ely, one of the critical problems usually experienced is the dirt and crud that builds up in the sharpener clamp.  If the band isn't held tightly in the clamp, the grinding wheel can move the band forward as it comes down the face of the tooth and tilt it backwards as it rides up the back of the tooth.  That changes all manner of tooth geometry.

Understand that I can't speak for the new CBN sharpening wheels.  I've not used them.  Their operation sounds like they take some of the art out of sharpening, and that might be a plus when it comes to crud or creatively shaping the tooth.

paul case

pineywoods and ely,
i dont have a full profile sharpener. it only grinds the face. here it is.




probably this is the problem. the most reasonable fix for me right now is to run the blade that i can sharpen that doesnt ''act badly''. pc
life is too short to be too serious. (some idiot)
2013 LT40SHE25 and Riehl edger,  WM 94 LT40 hd E15. Cut my sawing ''teeth'' on an EZ Boardwalk
sawing oak.hickory,ERC,walnut and almost anything else that shows up.
Don't get phylosophical with me. you will loose me for sure.
pc

NMFP

Check the flatness of your bands.  Lay a straight edge across the band from the gullet to the back and check both sides for even light or unevenlight.  The band must be held semi flat and have atleast a 2' section to check the flatness.  This is a common problem with 1.50" bands that are .042-.045" thickness.  Not as much though with thicker bands or narrow bands.

If the band rises in the cut, the band is "curved up" and if it dives in the cut, the band is " curved down" meaning, the band is going to cut in the direction the band is laying which is not flat.

I Check all bands at each sharpening and only flaten the ones that need flattened. Typically if the band will not saw straight, it is one of 3 things:
Incorrect hook angle
uneven set
band flatness.

Thanks,
NMFP

paul case

my band blades are 1 1/4 x 7/8
life is too short to be too serious. (some idiot)
2013 LT40SHE25 and Riehl edger,  WM 94 LT40 hd E15. Cut my sawing ''teeth'' on an EZ Boardwalk
sawing oak.hickory,ERC,walnut and almost anything else that shows up.
Don't get phylosophical with me. you will loose me for sure.
pc

ely

paul i would say that tom nailed your problem in the first diagnosis. i thought you had a cat claw sharpener. i misread.

logwalker

I experience those symptoms when I let the setter get out of adjustment. Too little on one side will cause that to happen. Do you have a way to set your blades and check them for accuracy?

Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

paul case

my setter does a good job and i do spot check with a caliper micrometer. my setter is a pineywoods $1.98 dual tooth setter. pc
life is too short to be too serious. (some idiot)
2013 LT40SHE25 and Riehl edger,  WM 94 LT40 hd E15. Cut my sawing ''teeth'' on an EZ Boardwalk
sawing oak.hickory,ERC,walnut and almost anything else that shows up.
Don't get phylosophical with me. you will loose me for sure.
pc

Larry

Quote from: Tom on May 10, 2011, 11:28:32 PM
Yes, hook is a reason, but so is tooth height.  It's a syndrome called "push-off" and can happen when the gullet fills too quickly.

Some style of bands have a much bigger gullet than others.  I would think with your style of sharpner a band with a bigger gullet would work better.

Gullet size is directly proportional to feed speed before bad things start to happen.

If you have a technical interest.

Bandmill blade calculator
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Kansas

We never got into band rolling but it looks like we are going to. When the Amish guy had a load of lumber delivered to us, he came along for the ride. He looked our operation over, and had a good talk with the guy that comes in twice a week to sharpen blades for us. He explained how they rolled their blades with a homemade roller. The guy that sharpens blades is a retired machinist and its always frustrated him that one blade he sharpens will cut fine, and the next won't. He plans on making a roller that will install just before the setter. I don't have a lot of faith it will help but he wants to try it. He has been checking flatness and seeing a fair amount of variance, especially on the 2" blades. Won't hurt to try.

Larry

With tweaking THIS could be the heart of a low cost band roller.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

NMFP

Rolling the bands is critical for proper sawing.  I sharpen, set and roll approx 70 bands per week along with my own and about every 3rd band will need rolled.  I have picked up bands that other companies have sharpened that will not cut correctly and all i do is roll them and check the set and they cut like new.  The entire process of reconditioning bands is basically 4 parts:
Cleaning
Sharpening
Setting
Rolling

Dont under estimate the value of flattening bands.  You can have a 50K mill but without properly sharpened bands, its not worth anything.

if you need help with flattening, please ask.

Thanks,
NMFP

scor440

Cooks saw and others swear that the blade needs to be run through a roller to flatten it back out to prevent the problem  you mention.Dont know if it is true .Cooks has a video and info.

tyb525

Get a roller and see if it helps. Some swear by it, others don't see it as necessary.
LT10G10, Stihl 038 Magnum, many woodworking tools. Currently a farm service applicator, trying to find time to saw!

AvT

I recently got the free video from Cooks.  On the sleeve it says they are good at making equipment but not good at making videos.  Well I beg to differ.  It is an excellent video.  I feel guilty that I didn't pay anything for it but will probably buy a roller from them somtime.
Wannabe sawyer, Cord King M1820 firewood processor Palax KS35 Ergo firewood Processor, 5403 John Deere, Bunch of other farm equipment,   LT70 Remote Woodmizer.  All good things but the best things in life are free.. If you don't believe me.. hold your breath for 2 minutes

NMFP

I am a firm believer that rolling must be done with bands.  If the band needs to be flattened and you do not have a roller, how else would you do it?

The rollers are fairly easy to build.  I purchased one from a Sponser here on the left but have also built my own for higher volumes of bands at any given time ** electric powered**

Please dont under estimate the value in rolling bands.  I have some customers that have had the same bands sharpened, set and rolled over 10 times.

If you need help with any rolling problems, please ask.  I know when I started years ago, i wasnt sure on rolling but everyone sooner or later finds the value in flattening bands and maintaining happy customers!!

8) 8) 8) 8)
NMFP

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