Troubleshooting Cracked Band Saw Blades
Advice on what causes bandmill blades to crack, how to prevent it, and whether it can be repaired. January 25, 2010
Question
I have several problems with some resaw blades:
One blade (Timberwolf silicon blade: 131-1/2" x 7/8" x .035" - 3 pos c) has developed a crack starting from the base of the gullet to the back of the blade (see photo). What would cause this type of crack/rip? Should I try to repair it as is, or cut it completely and reweld it? I do not have a blade welder. Can it be brazed or soldered (I have the skills and tools to do either), or TIG welded (may be able to find one, and I have the skills also) or must it be a special welder?
I have a blade similar to the above that is bent just enough so it tracks wrong (got bent while trying to put it on and not paying attention). Can it be straightened? What is the best method to restore shape?
I have another blade (received from the factory) that was welded out incorrectly - it has an arch to the back of the blade. Must it be cut and rewelded to be corrected?
Click here for higher quality, full size image
Forum Responses
(Sawing and Drying Forum)
From contributor N:
What type of machine do you use these blades on and how expensive are they? I have a Wood-Mizer LT 70 and I use the Wood-Mizer blades. If I had these problems I would probably just buy another blade, because it seems like what you would have to do to make your blades right would take enough time and money that you could purchase a different blade. As far as the crack, we get that if our blade has gotten hot due to misaligned blade guides. I have run other types of blades and I am pretty happy with the ones I get from Wood-Mizer.
From contributor O:
I have had lots of blades break - that's what they do. I also switched to Lenox - they last longer.
From contributor R:
Running the blade dull, running the feed to fast, guides seizing up or being seriously out of adjustment - any of these will cause the blade to heat up and case harden in the gullet area, causing it to crack.
If you know how to properly anneal the weld and re-anneal the whole blade then you could, but it would probably be cheaper to just buy a new one.
From the original questioner:
The machine is a 17" Grizzly band saw. The blade is a Timberwolf brand - which I think is a really good blade - as good if not better than Lenox (based only on my limited experience with both).
I'm as concerned, if not more so, about what is causing the problem as I am about repairing the blade. Of the possible causes listed above, running the feed too fast is the most likely, since the blade is still relatively sharp and the guides are fine. However I'm still confused as to what caused the direction of the crack - from the gullet toward the back as opposed to the opposite. I've pulled up all the troubleshooting info I could find and none of it mentions anything about a crack in this direction.
As for just tossing it out and getting a new one, well, right now I have a lot more time to waste than I do money, and I'm just one of those freaks that hates to throw away things that are partially broken (it only had 5 - 10 hours use on it).
As for the other blades... If it's possible to straighten them out in 10-15 minutes with a little bit of effort, why not? I would spend that much time ordering new ones and not getting the needed exercise.
From contributor L:
I suggest you take the cracked blade and the mis-welded one back to where you got them and get a refund or replacement. The bent one, you'll have to eat. You may be able to straighten it, but I never have had much luck at it.
From contributor R:
5 to 10 hours? It is more than likely duller than you think.
From contributor A:
The reason it cracks is the feed is too fast, so the dull tooth has to work too hard to cut the wood and it bends the tooth back and cracks it in the weakest point, the bottom of the gullet. Most of the time it is something that simple.
From contributor S:
What size are the band wheels on that machine? Is the blade that cracked 7/8" wide? I use 1.5" wide blades but run them on 26" wheels. The smaller the wheel, the more stress you are putting on the blade. You can try welding it, but the blade might not run right. Throw out the bent blade and send the mis-welded one back to Timberwolf. If you call Timberwolf (Suffolk Machine) and tell them what equipment you are running, and what you are trying to saw, they'll recommend a blade for you. I only run my new blades about 2 hours before taking them off for sharpening, so 5-10 hours of run time is pretty good.
From the original questioner:
The wheels are 17"; the blade is 1" and is the max width that can be used on the saw. The cracked one is the Timberwolf. I don't know if they'll take it back; they may just say it's my fault. The miswelded one is a Grizzly brand and they have a 30 day return policy. The Timberwolf blade requires less tension (or so I read after the fact), so it may be I had too much tension in addition to other factors. Anyone know if it can be brazed or soldered?
From contributor H:
The cracking you have is caused by metal fatigue - the constant bending and straightening of the blade as it goes around the wheels. It will always crack in the gullet between the teeth. It is the weakest part of the blade. How long do you expect these blades to last for a 17" Grizzly bandsaw? Welding or brazing and resharpening will cost you near what a new blade costs. The miswelded one, send back to be rewelded. The bent one and the cracked one are yours to keep.
From contributor T:
I agree with others about the blade being run too long. That's another way of saying it got dull and was pushed too hard. When a blade gets pushed too hard, the back of it will get pushed hard into the blade guide roller. The blade will bend slightly backwards at the point it goes over the guide roller and this will spread the gullet open at the front. This repeated flexing will cause micro cracks to appear in the gullets. Proper sharpening will not only get the points sharp but will also re-profile the gullets and remove the micro cracks - that is unless they have opened up too far.
I don't think you'll have much luck with welding these blades using the techniques you describe. Using a purpose-built band blade welder would do the job. But, by the time you cut out the bad sections, will there be enough length left to make a useable blade? Adding sections would correct any shortage. But I wonder about adding new pieces to an old blade - I have the feeling the new and the old would be too different in profile and flex to make a blade that would hold up.
Cooks has a band blade roller for bending a blade back flat. But it's intended to take the front to back cup out of blades that develops when they have been run on steel band wheels. I don't think it was intended to work out kinks. I've read posts by a couple others that said they took their time and hammered them out. But you need to be familiar with all aspects of band care and maintenance so you're sure the set is still okay, etc.
From contributor S:
I realize you are trying to salvage a blade, but it's just not worth the effort. I don't think those blades cost all that much - $15 or so? Would a 3/4" wide blade resaw just as good and give you longer life? What width material are you resawing? I'd keep a 1" wide blade for really tough resaw jobs, but then take it off and put a 3/4" on for more everyday resaw work. If you are resawing exotics like rosewood, most guys I know use a bigger machine and run carbide tipped blades.
From contributor S:
Correction: I checked the website; Timberwolf blades like the one you have retail at about $40. But these blades come in a bunch of different variations. Perhaps a different blade variant would provide better run time? If you must, go ahead and weld the crack, grind it and see what happens, but if the blade already has 5-10 hours of run time, it's probably dull anyway and isn't going to run correctly. I sharpen my blades after about 2 hours of sawing.
From contributor E:
As a band is used it develops very small micro cracks in the gullet. They are removed when sharpened when the face of the tooth is ground then down in the gullet and up the back of the next tooth. If you go too long between sharpenings, the micro crack develops into a full blown crack like yours, and bingo - it breaks. That is another reason not to run blades too long between sharpenings. I have tried welding blades by mig but they will crack, because in a factory they heat treat the weld area very carefully. If you don't heat treat they will break or become brittle. I purchase my metal bandsaw blades on a 100 foot roll. I make a lap joint of approximately 3/16 inch, then made a fixture to hold them straight, and put some paste on, then silver solder. I have had them hold until all the teeth wear just about off. I have not done this to my bandmill blades.
From contributor V:
A 17" wheel is real small. Does your wheel have a rubber band the blade rides on or is it steel on steel? If not running on rubber, make it that way. Also .035" is thin. We run minimum .042" -.055" thick. 2 hours on blade change - never go more, even if it's still sharp; blade needs to rest. As far as fixing it, don't bother. If it takes half an hour, how much wood can be sawn? These blades are throwaway.
From contributor L:
How long was the blade actually on the saw? It would take me a long time to put 4-5 hours run time on a shop saw.
From contributor B:
I also think it is time to throw that blade away. I bet if you put a new blade on it you would realize just how dull the one you are using is. If you are paying $40 for a 1" blade, I would look for another source. I think Cooks Saw makes a 1" blade.
From the original questioner:
The 5 - 10 hours is not actual run time. More accurately it is probably about 200 or so linear ft of cutting. However, the blade was still relatively sharp even with the crack in it (I only stopped to see what was making all the noise!).
Actually $40 (including shipping) for a 1" (decent) blade is average. I don't believe Cooks had a blade I could use on my saw.
I'm resawing 8/4 (basswood, birch, ash) into 1/8" and 3/16" x 7" pieces. I do understand everyone's business attitude of "don't waste time if it's not producing money." However, currently this is not a full time gig for me and since money is tight and I have time to burn, I thought I would attempt to salvage what was a good blade. But I'm also not going to lose sleep over it.
Contributor E's posting about silver soldering was what I was hoping to hear. Even if I spend 2-3 hours in the shop and it doesn't work, better than 2-3 hours in front of the boob tube!
Again, I really appreciate the input. (To think not too long ago one would have to go down to the local pub after 5:00pm to get this much knowledge and advice!)
From contributor G:
Timberwolf has sharpening and welding centers in their catalog. Also you can call them - they are very helpful. I don't see these as throwaway blades, but they must be re-sharpened and set before they get too dull or they will crack. It costs me $8 plus shipping to have them sharpened and set at Gooseneck, as opposed to the cost of a new blade.
6/14 #22: Band Saw Blade Problems ...
Alan
alancooper@bucksbedrooms.co.uk
From contributor Z:
I have a large bandsaw, not a resaw, and run a 1 1/2 inch blade on it all the time. I used to get frequent breakages, often failing on the joint. I complained to the blade supplier and they said it was due to not slackening off when not in use. Used too frequently for that bother, but since slackening off a bit, have not had to change the blade for absolutely ages, so observation is too tight a blade can increase breakages. I also think a good traditional blade weld is better than a modern machine made joint. I am in the UK and Quicksharp near Buckingham do traditionally welded blades which are very good.
From contributor P:
Cook Saw can put a blade on any machine. Those people know what they are doing. Also, I used the Timberwolf bands - best band I could find until Cook. But sometimes there are faulty bands, and it looks like you got one. Accept it, send it back, and move on. Not every band will be perfect.
