Jamie Buxton
08-02-2006, 8:00 PM
Occasionally on this forum or ones like it we see a post from somebody who says "My bandsaw blade has a kink in it. How do I straighten it out?" On further dialogue, it turns out that the kink is front-to-back, not side-to-side. The answer to the poster's question is that he should buy a new blade, because the old one is breaking. I caught a blade doing this, and took a picture to show folks who haven't happened to see this.
What is happening is that the blade is work-hardening. Eventually the work-hardening causes a stress crack across the blade. When the crack crosses the blade partway, the blade is continuous only on one edge, but not on the other. However, it is still being stretched over the wheel at both the front and the back, so it kinks at the crack. While it is on the saw, the stress crack is very fine, and very difficult to see. I found this one only because I could see where the kink occurred. For the photo, I coiled the blade up, which acted to open the crack.
To give you a sense of scale, this blade is 3/4", 2 TPI.
What is happening is that the blade is work-hardening. Eventually the work-hardening causes a stress crack across the blade. When the crack crosses the blade partway, the blade is continuous only on one edge, but not on the other. However, it is still being stretched over the wheel at both the front and the back, so it kinks at the crack. While it is on the saw, the stress crack is very fine, and very difficult to see. I found this one only because I could see where the kink occurred. For the photo, I coiled the blade up, which acted to open the crack.
To give you a sense of scale, this blade is 3/4", 2 TPI.