Gullet cracks

[kelLOGg]

When I see my band blade oscillate in and out when idling I know gullet cracks are starting to form. Typically, the oscillation worsens over a few minutes and I may find one or more cracks about half the width of the band before it breaks. This has been a pattern for years – until yesterday. I removed the band to set and sharpen and noticed a gullet crack half the width of the band but there was never any oscillation. I recycled and replaced it. What indications do you observe prior to band breakage? I am puzzled why the current example showed no oscillation which previously had been very typical.

[Southside]

The "tick,tick,tick,tick,tick" of the band passing by the roller guides is letting me know it's not long for this world. 

[Gere Flewelling]

Bob, I have noticed a similar occurrence with my blades as well.  I catch them most of the time by the tell tale wobble.  I did find one this summer while sawing a large quantity of hemlock, that  started to do the wobble.  When I checked for the expected crack, I couldn't find one on that blade.  This was a blade that I had struck metal and just ground the teeth down slowly to reshape them.  I was just experimenting to see if I could reshape them and make it cut.  I think I ground down too deep into the gullet and weakened the blade. I put that blade in the junk pile.  The gullet cracks happened a lot when sawing this summer.  Most of the blades I was using had been sharpened many times.  I am wondering if I was focusing too much on following the bottom of the gullet every time I sharpened them and just ground too deep and weakening that part of the blade.  I know that Tim Cook mentions in one of his YouTube videos on sharpening that you should focus on the tip of the tooth every time you sharpen and only occasionally follow the gullet.  This kind of goes against what most believe need to be done when sharpening from my understanding.  I don't think the sharpeners using the CBN wheels have that option, but us "drag sharpener" guys are able to  do that.  Up until recently I was doing as Tim suggested, and only recently focused more on the full gullet grind.  It was then that I started noticing the gullet cracking with more frequency.  I think I am going to return to the original sharpening method I had been using. Another thing that came to mind is, this was occurring while I was sawing mostly hemlock.  Hemlock saws pretty well, but does have very hard knots. I wonder!

[Bruno of NH]

The tick tick tick let's me know 

[Ljohnsaw]

I don't see wandering, just the tic, tic, tic.  Except for the first 3 blades I ruined (one hit with the chain saw : and two pop-offs getting bent), I had only one break about 3 years ago.  This past summer, I've had 3 or 4 ticking time bombs.  What I saw was 2-5 gullets with cracks, all of which were within 4 or 5 teeth of the welds.  That tells me the welds were not perfectly straight or shrinkage after welding caused them to warp toward the teeth.  The tension on the blade then is concentrated on the inside of the gullet and any minor imperfections (scratches from sharpening?, micro cracks?) lead to failure.  Granted these blades are 4-8 years old and have been sharpened probably 5-8 times.

[KenMac]

I don't know what brand blades you use, but the Cook's SuperSharps  I run will also move in and out when gullet cracks are present. I always check by looking at the bottom of the guide rollers.
I haven't seen one in a while even though I'm still running the blades probably duller than I should. They seem to be worse after sharpening. I run 1.5" x.055" blades and they probably crack sooner than thinner blades.

[kelLOGg]

Interesting, some get tic, tic, tic and some get the in and out phenomenon. I am running Kasco 1.25", .045", 4° and I got the same issue with Cooks bands.

[KenMac]

I wonder if the different effects cracks show is due to the difference in wheel type-- crowned steel as opposed to grooves with belts?

[kelLOGg]

Interesting and reasonable interpretation (except for my last band)
I hope the in/out re-appears for me because l like the warning that cracks are forming.