55 cracks in one band blade

[jackpine]

 Well, really only 53 cracks because the band broke in two places. When I sharpened that band yesterday I noticed three small cracks at the root of three teeth and debated about just throwing it away or using it until it broke. Because I didn't see the cracks until after sharpening I took a Dremel tool and etched the location of the cracks to be able to tell which one the band broke at and decided to run it today sawing small white pine. After 250 bdft it started to flutter but as usual I thought " just one more board" and of course it broke about 12" into the cant. When I looked at it closely I could not believe how many cracks I saw so had to count them. The funny thing is it did not break at any of the three original crackls :D I think I will keep the two pieces as mementos.

Bill

[Tom]

It's amazing how quickly they deteriorate once they begin to work harden, isn't it?

You can do some diagnosis work when you see where the crack starts.  I have no metallurgical training but I understand from reading that the cracks at the base of the face of the tooth can be from having a too sharp transition angle or from driving the band too hard.   A crack in the middle of the gullet is more likely to be from a groove or divot in the surface where the grinder was dropped or the stone not dressed properly.  I guess heat from grinding too hard or too fast might do it too because it would heat spots that might make them more susceptible to cracking.   'Course the cracks in the back of the band are from running the guides too far away from the back of the band.

It's probably safer not to put a cracked band back on the mill, but it sure makes for a fun experiment, doesn't it?

Did you jump?  :D

[paul case]

i always worry about the belt inserts on my bandwheels when a blade breaks. them wheels are spinning fast and the teeth on the band wouldnt have to touch the belt much to tear it up badly. i always try to watch for the band behaving badly and get it out of the cut so i can find the crack and trash it before it messes up something else.
pc

[jackpine]

Tom, You are right about why the cracks formed at the base of the tooth. I redressed the stone  last week and had too sharp of a transition, i.e. not enough radius, at the base but thought it would wear in after a while. After 35 years of machine design where one always puts a radius or undercut at such points you would think I would pay more attention :D
No harm done as these were my logs harvested for my lot because the trees were dying from blister rust. I see the blade flutter and know it's going to break and still jump every time.

[ladylake]

Cracking in the gullet, make sure the guide flanges aren't too close to the blade.    Steve

[bandmiller2]

Seems like cracks always get discovered after you set and sharpen a band.Once you see one crack the rest will follow.Everything Tom mentioned contributes to the demise  of a band but the biggie is flex hardening,the band can make only so many trips around the wheels.Frank C.

[Norm]

I don't know how many blades I've broken but I still jump a foot every time. :D

[customsawyer]

Its like walking around a corner in the woods and seeing a snake you must first jump and turn in mid air then decide if it is poisonous before landing.

[Magicman]

Customers often ask "can you weld it back together".  Even if you could it wouldn't last long because the entire band is work hardened.  It would just break somewhere else.

[pineywoods]

Customers often ask "can you weld it back together".  Even if you could it wouldn't last long because the entire band is work hardened.  It would just break somewhere else.

I was too dumb to know that, so I tried welding back broken blades, several times. Tried different methods, torch with stainless rod, torch with mild steel rod, brass, mig, stick welder. Even took some to a saw shop that used a resistance welder.They seldom lasted long enough to get dull. Definitely not worth the trouble.

[jackpine]

Update on the cracked band I put in to finish the log. It finished the last 3 boards and cut well so I slabbed the next log and cut 105 bd.ft. from it. Then slabbed and cut the flitches from a 20" pine. At that point common sense finally sunk in and I pulled it. The crack did not appear to have grown too much but now there are 2 more cracks on adjacent teeth. Retirement time :D

[ladylake]

How many sharpenings are you up to when they start cracking?    Steve

[jackpine]

Steve, it's hard to tell because all of them were sharpened at least once by Re-sharp before I bought the sharpener last year. I tend to let dull bands accumulate and then set and sharpen on a rainy day. Then I'll go for several days setting and resharpening the same bands as I use them until I have to dump the water in the sharpener. An educated geuss would be 4 min. and as many as 8 on some bands that seem to go on forever. I do have some older bands that seem to have a different steel than the Doublehards as the are more flexible and seldom crack regardless of number of sharpenings.
Bill

[Chuck White]

I usually get 6 to 8 sharpenings before they begin to show signs of failure!

If the band has 1 crack in it that can't be sharpened out, it goes to the scrap pile!