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3 broken blades

Started by davidn3, January 16, 2017, 04:15:06 PM

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davidn3

I have an old 90s lt40hd.  Sawing frozen pine right now.  Just got the mill in November.   Came with 9 degree blades.  I had them sharpened by woodmizer.   Now that the logs are frozen, seems like I get through 3 logs and the blade snaps.  Im using the debarker and today was 40 degrees outside and still broke a blade after 3 logs.  Do I need the 4 degree blades for frozen?

jmouton

i was having the same problem , broke 4 and hey were frozen oak ,,lots of wavy cuts , not good,  i called woodmizer and they said 4  would be better,    havent tried it yet but i think it will solve the problem or maybe try not to saw frozen wood , ha ,, i know it s hard to do this time of year ,good luck ,,,



                                                                                                               jim
lt-40 wide ,,bobcat,sterling tandem flatbed log truck,10 ton trailer, stihl 075,041,029,066,and a 2017 f-350,oh and an edger

davidn3

I did look at the broken blades and they have some cracks on the back end.  The guede seems to straight.   Doesn't tilt the blade one way or the other. 

ladylake

 

Frozen wood doesn't cause blades to break, something else is wrong and yes 4° saw straighter and better in frozen wood.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

YellowHammer

If you could take a close up picture of the break, it would be useful.  Depending on where the crack started, front or back of the blade, will give some clues as to what is happening.
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

davidn3

It's the back of the blade.  Can't get a good pic right now.  There seams to be a few stress cracks on the back of the broken blades.

bandmiller2

Sounds to me like those bands were at the end of their useful service life. There also comes a time when there are diminishing returns cutting when its real cold. Low temps are hard on equipment, mills and us if you don't have to wait for better conditions. Save the testosterone for fun stuff it doesn't belong in the mill. Frank C.
A man armed with common sense is packing a big piece

bkaimwood

X2 on the frozen logs...they alone don't break blades
bk

dgdrls

Agree with other posters, Frozen Logs alone will not
break three bands all the same way. 

Are the band guides adjusted properly for up/down and depth?  Guide bearings good?

Best
D


YellowHammer

Quote from: davidn3 on January 16, 2017, 06:02:23 PM
It's the back of the blade.  Can't get a good pic right now.  There seams to be a few stress cracks on the back of the broken blades.

In some cases, as was mine some time ago, breaking on the back of the band can be caused by the back of the band rubbing too hard or i termittedly on something, heating up, and becoming brittle.  The the cracks starts in the rear edge of the brittle metal structure and propagates to the front. 
So look for anything that may have a notch or grove or polish cut in it, including the back shoulders of the bearing guides
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

4x4American

^ what he said...frozen logs are sawable, but can be a bear, and any problems will really show.
Boy, back in my day..

tmbrcruiser

I had a problem too. Were they blades from Woodmizer? If so not the same problem I had.
Once you get sap in your veins, you will always have sawdust in your pockets.

davidn3

Went to the local woodmizer and got an alignment tool, wheel belts, and some blades.  After getting to belts on, the alignment looks perfect.   Maybe the old belts were allowing the blade to push back and riDE against the idler pulleys.  Will find out soon enough. 

esteadle

Did your bands break in the cut, or did they break while spinning/idling?

Materials fail due to stress and corrosion that combine to open up cracks that propagate further as the stresses are applied and then relax. This is commonly called metal fatigue. If the cracks in the blade are developing in the back of the blade and moving forward toward the teeth (as opposed to starting in the bottom of the gullet, and moving to the back of the blade), that suggests to me that there is significant stress on the back of the blade, but not on the front.

For that to happen, the blade would need to be deflecting backward in the cut, lengthening the back of the blade compared to the front, which induces additional stress in the back. That is certainly possible if you are really pushing the feed rate hard. It would also be more likely if the roller guides are wide apart, and the band isn't supported as it exits the cut. But you would also probably be getting a lot of wavy cuts and varying thickness lumber. Is that also happening?

You can address deflection either by increasing the blade tension, or decreasing the feed rate. Typically when you increase blade tension, you reduce the overall life of the blade, so that may not help. But slowing down a bit may give you longer blade life. If your blades are breaking while in the cut, this seems like it might be the problem.


If the bands are breaking while you are idling, you may have a different problem: mis-aligned bandwheels.

If your band wheels are not "co-planar" (in the same plane, if you were to look across them from the outer edge of the close wheel toward the outer edge of the wheel further away) the wheel axles could be turned into and toward each other, either in the front (teeth side) or the back. As the blade travels around the wheel, one of the edges of the band will need to stretch around the wheel, and that induces the stress in that edge, and then you fatigue that edge more quickly. Since your back edges are where your cracks are developing, I'd guess your band wheels may be turned in toward each other. The axles of the bandwheel need to be parallel to each other.  If you extend imaginary lines thru the axles, it's likely they would meet on the tooth side of the blade somewhere down the road.

To check this, get yourself a straight steel edge, long enough to reach the outer edges of each of the bandwheels. Lay it across both wheels about 1/2 way between the axle and the edge and look down the line of the steel edge. It should touch both edges of both bandwheels. If there is a gap between any of those 4 points, they are out of alignment. This test should be done both above and below the axle.

To align them, contact your mill manufacturer and ask them for a procedure. You may be able to adjust it enough with just the Bandwheel Tracking Adjuster Plate, or you may have to pull the bandwheels off of their shafts and re-set them, and re-torque the bolts using a torque wrench. After you do that, you might want to start keeping track of how long a new band lasts so that you can tell if this helps and confirm it's the problem.

Best of Luck.

Eric

Magicman

I understand what you are saying, but a blade could be almost broken and actually break during the next situation be it idling or sawing.  It will not "always" break during any particular operation regardless of which operation actually caused it to initially crack. 

During the past 14 years and many broken blades, I have had them to break in every different operation and position imaginable.  In the log, out of the log, beginning of the cut, and ending of the cut.  One actually broke in two places and threw a small section of blade beyond the log loader.
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

esteadle

I did not use the word "always".
I used the words "may" and "might".
I used those words on purpose.

4x4American

I took a blade off the mill yesterday night and noticed a nice crack in the weld joint.  If I made one more cut I bet it would have broke...and ruined the brand new belts I just put on.  So I broke it with my hands.  Once you hear that ticking, shut her down!
Boy, back in my day..

Magicman

Quote from: esteadle on January 20, 2017, 07:45:14 PM
I did not use the word "always".
I used the words "may" and "might".
I used those words on purpose.

I understood, but my words were for everyone reading as were yours.  The cause of blades breaking can be simple, elusive, mysterious, and sometimes just because they did.   :)
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

redprospector

I've had a lot of blades break just because they did. If I dug into it too deep, I'd probably find that it had something to do with my sharpening.  :o
I had 2 break the other day, what I considered way too early. I took a look at the Belts, and the $4.00 with free shipping B-56 belts from eBay had gone south in probably 30 hours of run time, or less. I installed new belts (not from eBay)...problem solved. So figuring in the cost of the 2  broken blades, those $4.00 B-56's cost more than the good belts (and were way harder to install). I think it was a classic case of, You don't always get what you pay for, but you'll always pay for what you get.  ;)
1996 Timber King B-20 with 14' extension, Morgan Mini Scragg Mill, Fastline Band Scragg Mill (project), 1973 JD 440-b skidder, 2008 Bobcat T-320 with buckets, grapple, auger, Tushogg mulching head, etc., 2006 Fecon FTX-90L with Bull Hog 74SS head, 1994 Vermeer 1250 BC Chipper. A bunch of chainsaws.

Kbeitz

Every one of my blades break... Because i run them until they do.
That's when I know the blade is finished. I was silver soldering them
back together but they don't last very long afterwards.
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

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