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The hidden enemy of Bandsaw Blades

Started by prittgers, September 14, 2014, 10:48:50 PM

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prittgers

It's easy to blame the dirt and grit in the log for the seemingly short life of our expensive bandsaw blades.  There is a hidden destructive force, though, that makes razor sharp blades break with a frightening bang.  The terrorist is actually the stress of the blade flexing and straightening as it moves round and round the wheels. 

As one who sharpens a lot of blades for both pro and hobby sawyers, I have come to understand that a good operator knows that about 2 hours on a mid-sized mill is all it takes to create these microscopic cracks. 

After several hours the blade performance drops and the sawyer usually takes it to the shop.  But, even though the profile and razor sharp cutting face can easily be restored - the hidden damage is the stress crack. 

Keeping your run time to about 2 hours and having the blade precision ground eliminates these cracks.  They are forced to start forming all over again - vs simply quickly propagating down through the gullet.

A good grind eliminates these life-robbing stress cracks!



 
Parker Rittgers
Professional Sawyer, Retired, well, not really !
WoodMizer Alaska | 907.360.2497 cell 336.5143 office BevelSider.com ? Everything BevelSider
907.336.5143
prittgers@aksamill.com

Chuck White

Good point!  smiley_thumbsup

I've found that to be quite accurate!
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

5quarter

Excellent photo of the trouble. notice the cracks are to the top side of the blade which is always under tension around the wheel, while the bottom is always under compression. Time in service though really depends on the composition of the steel, thickness of the band and the degree of radial curve. using a thinner blade body, a more malleable steel and larger bandwheel would likely extend the run time significantly.
What is this leisure time of which you speak?
Blue Harbor Refinishing

DMcCoy

Quote from: 5quarter on September 15, 2014, 01:31:44 AM
Excellent photo of the trouble. notice the cracks are to the top side of the blade which is always under tension around the wheel, while the bottom is always under compression.

Also they are in the gullet where the blade is narrower and takes more of the bending.

This is a great topic, Thank you!

EZ

Looking at the deep of the cracks it looks like I need to sharpen my blades 4 or 5 times in order to get read of the cracks. Is this what you guys do. EZ

scsmith42

Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Chuck White

I don't run my blades to the point where they're "really" dull, so I have been having pretty good luck just setting them and giving them a light grind!
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

drobertson

It should be mentioned that certain blades inherit this type of cracking much more than others.  Most are of the microscopic nature.  these look pretty far gone.   I run a simple face grind on the tooth, have for several years now,, only the occasional break, mainly due to a chunk of debris that creates too much stress.  I do suppose cracks present are there, but have never seen anything like these shown.  I will admit, I'm not a blade sharpening specialist,  just a simple tool maker that likes sawing wood, if I ever see a crack like this shown I would just trash it for sure.
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

EZ

I do also have real good luck with my blades. I try and get read1000 .bf out of one but most of the time when they get to dull it gets harder to push threw. That will be my next thing I do on the mill is put had drive on it. If I can ever figure it out. It's probably been a couple of yrs since I broke a blade. EZ

hackberry jake

I'm impressed with how smooth the grind is on that band. Usually at that magnification, you can see grinder marks. Also, smaller HP mills can run a band through more sharpenings because the gullets don't see as much stress.
https://www.facebook.com/TripleTreeWoodworks

EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

Peter Drouin

Quote from: hackberry jake link=topic=77762.msg1180865#msg1180865 date=1410820083, smaller HP mills can run a band through more sharpenings because the gullets don't see as much stress.
/quote]



My cat eats them up, but It puts out a lot of wood too.
A&P saw Mill LLC.
45' of Wood Mizer, cutting since 1987.
License NH softwood grader.

hackberry jake

I would gladly trade out blade life for the performance of a big diesel. Bands are a pretty small cost in the big picture of things, and high hp mills get a lot more board feet cut before the band is too dull to keep going. They take a bigger bite

My mill = food1
Diesel mills = sketti_1
https://www.facebook.com/TripleTreeWoodworks

EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

Peter Drouin

Quote from: hackberry jake on September 15, 2014, 10:13:10 PM
I would gladly trade out blade life for the performance of a big diesel. Bands are a pretty small cost in the big picture of things, and high hp mills get a lot more board feet cut before the band is too dull to keep going. They take a bigger bite

My mill = food1
Diesel mills = sketti_1




:D :D
A&P saw Mill LLC.
45' of Wood Mizer, cutting since 1987.
License NH softwood grader.

shinnlinger

My Turner rolls around highway trailer tires.   That cushion of air absorbs the expansion and I have only broken one band (on a lag bolt) in the 7 years I have run it.

Why dont more mills don't run on tires?  I cut beams perfectly square.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

hackberry jake

At what blade width do you toss your blades shinnlinger? I haven't broken many. Mine either have a devastating metal strike that messes up the set too much or it gets close to 1" and I'll toss them.
https://www.facebook.com/TripleTreeWoodworks

EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

ely

i run a norwood, and with the 20 hp I know I load it up sometimes. being a manual mill I can feel when it gets dull so I change it. I run the catclaw sharpener and I usually only set the band about every third sharpen... I will get a band to break once in awhile, but it is most always on a band that has seen better days.
when the bands get too short that I cant grind the gullet on the catclaw they usually break the next time I use them... if I ever get one to last I will just face grind the teeth and saw a bit longer :D

I have noticed that after I use up almost 1/8" off the band that I do have to set more often, it seems the good steel that holds the edge gets ground off with use and the softer steel needs worked more often.

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