Bandwheel size and broken blades. What is the relationship?

[esarratt]

I have heard that smaller sized bandwheels can cause broken blades.  Anyone have experience with this?

By smaller sized I mean 16" vs 19" wheels.

[longtime lurker]

The smaller the wheels the tighter the bend radius the band has to travel around which results in increased metal fatigue.
Also the smaller the wheels generally the smaller the horsepower driving it, which forces you to use thinner gauge bands that are yet more vulnerable to metal fatigue.

Fundamentally bigger is better.

[barbender]

I'm going to differ with longtime in the thin blades being more subject to fatigue, at least on the 19" wheels on my Woodmizer LT40, bands up to .045" seem to last nearly forever, whereas the heavier .050" and .055" blades will only make 2 or 3 sharpenings before they break. 

[Dave Shepard]

.045" last until they can't be sharpened anymore, .055" I get 4 sharpenings on LT40 with 19" bandwheels. 

[firefighter ontheside]

It's all about how much a given thickness of metal wants to flex before it starts to break.  Thinner metal will flex more, so it can go on a smaller diameter wheel.  Therefore it makes sense that thinner bands will last longer on a given wheel size than thicker bands.  

[Will_Johnson]

Bigger wheels and thinner blades unquestionably increase blade life.

But I assume your interest in longer blade life is, at least in part, related to getting more value from your blade dollar.

If so, it's worth considering that while bigger wheels offer longer life, they also require a longer blade. So while you will save money by getting longer blade life, you will spend more on the blades themselves.

So it's about finding a balance that works for you.

There are similar trade-offs with blade thickness. Thinner blades are less likely to break due to the bending stress of going around the blade wheel. But they also have less beam strength, which means they're more likely to deflect in the cut.

Again it's about finding balance between various positives and negatives.

To a great degree the industry consensus seems to have settled around ~ 19" band wheels and ~ -0.04-0.045 thickness.

That doesn't mean there isn't room for dissenting ideas, or that a given situation might swing these balances out of balance.

[tacks Y]

I know Timber King makes a tough mill but to run 7/16" blades? Maybe .040-.045"?

[Southside]

One additional factor is how the band is heat treated or otherwise finished when new.  I used to run WM double hards, but now only run their Silver Tip band as I get longer total BF out of a band and a lot fewer broken bands.  For whatever reason the Silver Tip has better flex life.  

Although I run a lot of WoodMaster tooling in my planer and moulder, and I am very happy with it so they are my source for all of my knives, I have never run a TimberKing band so I can't comment on how they compare.  No Will - that's not a hint of any kind.   :D  :D  :D

[longtime lurker]

Just to clarify about the thinner band= lower band life comment I made, I agree with y'all that a  thicker band will flex less going around the wheels which reduces band life. And I also agree that a thinner band that flexes more will theoretically last longer, but it won't cut so straight as a thicker band. That's theoretically.

In the real world we all get paid for straight evenly sized lumber (and if it doesn't pay more then it definitely sells faster). So when you run the thinner band (or at least when I run the thinner band) I find it necessary to up the strain to keep it tracking well. And thinner (19 gauge) bands + high strain + fast feed equates to lower band life, at least in my limited bandsaw experience.

With these big old bangers like mine there are really only 3 band thicknesses readily available (here, other places may vary but I suspect not cuz these things are like crocodiles, basically dinosaurs but still incredibly proficient and quite able to eat ya)... 17,18 & 19 gauge, which is 0.045, 0.040, and 0.036 respectively, though I'm sure you can go thicker or thinner by the coil. Which makes the point that beam strength in a band has little to do with band thickness and a whole lot to do with band width. What I'm yet to learn is the long term economics, but what I do know is that big wheels + band depth makes for fast feeding and lotsa wood. ;D

[Deese]

I'm curious if anyone has successfully fitted their LT40 with larger bandwheels. I saw everyday and use 1.5" .055"s because they consistently produce flat lumber. A local friend of mine uses the same size blades on his Cook's AC36 with 26" bandwheels. Needless to say, he gets significantly longer life from his bandsaw blades compared to my 19" bandwheels. 

[customsawyer]

I don't think you have enough room inside of your guards to do that but it's been a long time since I looked that close at a LT40. I know you can fit a LT70 where a LT40 fits.  :D

[ladylake]

 
  There a more reasons for breaking blades too soon  like having the guide wheel flange too close to the back of the blade ( biggest reason), running a dull blade too long, pushing way too hard  etc.  Steve

[jimbarry]

 There a more reasons for breaking blades too soon  like having the guide wheel flange too close to the back of the blade ( biggest reason), running a dull blade too long, pushing way too hard  etc.  Steve

Also, worn belts on the wheels, and, misalignment of the blade on the wheels.

[YellowHammer]

I'm curious if anyone has successfully fitted their LT40 with larger bandwheels. I saw everyday and use 1.5" .055"s because they consistently produce flat lumber.

No, but when I changed blade manufacturers or alloy for the same .055's on my LT40 I went form "bang" to "boredom" because was easily doubling band breakage time, basically getting to the point were the bands were being resharpened too much to fit the guide wheels.  If you are using Double Hards, they break (past tense as in broke, because I do not use them anymore) much more frequently than some others of the exact or nearly exact configurations.  I also stopped chewing ip so many band wheel tires due to the blade breaks.