Something to discuss on blades

[gmmills]

  That link is not good. try this one.   http://www.rixsaws.com/page4.html   

[Ga Mtn Man]

gmmills-

What is the theory behind a less aggressive tooth angle giving better performance on a higher powered mill?

[MartyParsons]

I've been having trouble breaking blades and someone told me to swap em every 90 minutes...I had been running them til they got dull.

Do we want to discuss this?
  If you are having issues like this then ask these questions.

Where did the blade break?
   If it broke at the weld and it has never been sharpened then it is a good chance it is a bad weld. If it broke at the gullet then it is most likely a flex life issue. We recommend 500 to 800 bd/ft per sharpening. If you are running the blade longer that that then the stress cracks are forming and will not be removed during the sharpening process.   
Who is sharpening you blade?
I have heard it a few times. "You only need to sharpen the tooth". Well yes that is correct to make the band cut, but the cracks form in the gullet and they need to be removed. It they are not removed during the sharpening process then the blade will break at these stress cracks.
I would think every band saw owner needs to be aware of the flex life of the band. I very thin blade like .035 will flex for a long time and a very thick blade like the .055 will flex less. What do you give up with a thick blade? Flex life. What do you give up with a thin blade? Beam strength or resistance to dive during the cut. A thicker blade will also use more hp. If you have a 10 hp gas engine band saw and put a .055 blade on and cut then you would be wasting money on the blade because the increase performance would be wasted in loss of hp and flex life would be shorter. If you have a 35 hp or larger engine and you are sawing some lumber of more value and you have employees and every bd/ft must count then the thicker blade would have some value. Production and quality may be improved by using the stiffer blade.

There are a few other things that may make the blade fail or have a short run time. Tracking, ( pushing the blade back into the guide) Heat. Belted wheels. Sap under the band wheels causing the blade to bend or flex more often. Wheel alignment.

During training I always ask them to be Sherlock Homes when they have a blade failure. I have seen some throw blades in the scrap before trying to solve the issue. If you stop and look at the failure then recognize what caused it things will work much better in the future. 



Hope this helps.

Marty

You asked a question about why I refereed the 9 degree frozen blade as a 9/29. I guess to clarify the hook angle and the back angle all has effect on the performance of the blade. If you take a 10 degree 30 degree back angle blade and just change the hook angle then it would not be the same.

Comment on changing the degree of the blade to another angle with the CBN wheel. You will wear the wheel a little sooner than sharpening the proper hook angle blade with the proper angled wheel.

[Cutting Edge]

Comment on changing the degree of the blade to another angle with the CBN wheel. You will wear the wheel a little sooner than sharpening the proper hook angle blade with the proper angled wheel.

Actually, this CBN wheel was specifically engineered and manufactured for this application.  2 light passes with sharpener is all it takes.  The change in the profile could be measured in thousanths of an inch.  Once the hook angle is established, subsequent sharpenings are no different than any other blade.

[4x4American]

Thanks, Marty.  The reason why I was breaking bands was because the back of the band was hitting the flange on the guide roller.  I only had them set at 1/8" gap.  I now set them to 1/4" and so far so good. 

[roghair]

When pineywoods raised the question about the different angles I got confused... and found this picture.  Hope this helps for the discussion.



Also the question from Ga Mnt Man came to my mind reading this tread, any answers from the specialists?  :P

gmmills-

What is the theory behind a less aggressive tooth angle giving better performance on a higher powered mill?