Breaking bands

[Larry]

I have been running my bands with more tension for the last year or so (and getting better performance in the knots).  My band breakage has went up slightly (expected) but I am beginning to see a trend.  They are all breaking from the back.

I don't believe the manufacture is a factor...I got some from about everybody and breaking all of them.

Guessing this band has been resharpened more than 6 times as it only measured 1-1/16" wide.  A WM band but the gullets are my own design.  The band had 3 different pairs of breaks just like the pair pictured and one single break.  I was getting ready to set it when I noticed the breaks...it came off the "Hit metal peg".




I'm running my bands 1/8" or little more off my back roller...thinking with the increased tension this may be to far.  What do you guys think and how far are you running your bands off the back?

This it not a big problem for me as the breakage is still DanG low and most bands are biting the dust from getting to narrow.  Just like to tweak to get the best performance I can get.

[Gilman]

Looks to me like too much feed force combinded with the higher tension you were talking about.

[Grawulf]

Larry,
I was running my bands about the same off of the back bearing.........and having the same trouble you're having. I brought them up to less than a sixteenth and the stress cracks magically disappeared! If you're changing back and forth between different brand bands, you may have to do some dinking with the adjustments to keep the band running close to the back guide but the time spent is worth it - I don't seem to get as much waver in the cuts anymore either.

[Tom]

That picture is a classic example of having the roller guide set too far back so that there is too much room between the back ledge of the guide and the band.  Or, in other designs, too much room between the back roller and the band.

Cracks like this could also be caused by the bandwheels not being co-planer but the guides out of adustment would be the first diagnosis.

[ladylake]

Larry  I run mine real close too 1/16 or less.  Seems to help.  Also make sure your v belts aren't wore so much that the blade is hitting the metal on the wheels, that will break blades real fast.  On the other hand six sharpenings isn't to bad.    Steve

[D._Frederick]

Your back-up guide roller should have no more than 0.025 inches from the blade when the blade is tensioned. With this clearance the blade should touch the back-up roller only when the blade is cutting.

You may be over tensioning the band, I run my blades 1 1/4 x 0.042 with 1100 lbs of stress.

[ARKANSAWYER]

  I run my blades at 2300 psi (0.045 10 degree WM's) and about 1 /16 off the back of the rollers.  If I start breaking blades I look at my V belts and most of the time they are worn out.  I go through about 3 sets a year or about every 100,000 bdft.  Like Steve said "Six sharpenings is not bad"  Most of mine bust by 5 or are to narrow to sharpen.

[Larry]

Thanks guys.

Gonna change my clearance to 1/16 this morning.