|Home » Forums » Solid Wood Machining Forum » Message||Login|
You are not logged in. Consider these WOODWEB Member advantages:
broken bandsaw blades12/4
My band saw blades invariably develop a stress fracture well before getting dull. It's no fun when the blade breaks (sounds like a gun shot) so I take them of when the tell-tale thumping becomes pronounced, as the fracture passes through the guides. I just assume the blade is no longer viable, but could the partial break be welded back (I typically use a 3/4" hook tooth 3tpi. 145" long on a Laguna HD16.) And what specific type of welding is needed, as I would need to find a welder to do it.
Band saw welders were once so common that they came attached to the better bandsaws, so you could make up blades right there at the saw. People weld the saws and you are people, so you should be able to learn it. You can buy band saw coil stock in 100' lengths of whatever type tooth pattern you like.
Yeah, I could learn orthopedic surgery too--it's pretty much bloody carpentry--but I'm an old dog and not looking to learn new trades. Actually I bought a couple 100-foot rolls of high-quality band saw blade stock and 2 different guys who had welders couldn't get the welds right. So while it's not rocket science it's not like putting some duct tape on a joint and hoping for the best. I'm sure professional welders will back me up.
How many of your blades break before getting dull? Always on the weld or other location? Are you just using it for resawing? You also don't mention the steel in the blade. Basically two types of welding, butt welding and flash welding. Flash welding is what you want. Also a skilled operator or high end machine that can do a quality annealing after welding. You don't want to try and do a partial weld. Cut the weld out, and then a new weld. I'd also guess the band is too thick for that size wheel if you are seeing that much breakage.
These are good blades "Morse" brand from Charles GG Schmidt). They never break on the original weld, but develop a fracture over time. I primarily rip solid stock, and only occasionally re-saw anything thicker than 8/4. Tony
You might want to check the crossline on your wheels. If you turn the wheels backwards (carefully) by hand the blade should stay put. If it moves forward or back you may need to align the wheels-they should be parallel.
I suggest you try a thinner gage blade, or try a 1/2" wide with that tooth count. You may be running too heavy of gage on those wheels, inducing bending fatigue.
As long as you aren't loading the blade in the guides with cutting too tight of radius, the only other mistake you can make is feeding too fast. After that, it's only tension and too thick for the size wheel that will cause issues.
I use a lot of bandsaw blades and can tell you they are not all created equal despite who sells them and what they say about them. Treat yourself to a Lennox Wood master B and carefully track usable time on the machine. You just might be amazed that the added cost will be easily repaid and them some in longevity.
x2 on AM's suggestion for the Lennox Woodmaster B blade. You can get them from CT Saw and Tool by UPS and many other dealers. Just because you are using a quality blade doesn't mean it is the best blade for your setup.
As to the stress cracking my experience is that the 16" band saw wheels (I'm assuming that's what they are from the model number) are pushing the limits in terms of radius for a 3/4" blade. If possible try switching to a 1/2" blade and see if you get better results.
After years of fine tuning blade tension and alignments I eventually got my Laguna 18" Resaw Master 1" x 3tpi Lennox Woodmaster B blades to last the life of the tooth without breaking from stress cracks. That was with an 18" wheel and I think yours is smaller. While it's the 3/4" blades you are having a problem with it is the same problem I had with the Resaw Master.
I suggest going to the Lennox blades and getting hold of a blade tension gauge to dial in the top wheel tension. Years ago there was a dealer in NY that lent out their tension gauge but they closed their band saw blade division. Perhaps you could find someone that has one to loan. You can't count on the tension gauge on the saw.
If your blade is deflected (contact) by anything other than blade transport wheel tires you're causing a slight momentary bend with every blade revolution. It accumulates metal fatigue at X repetitions per minute at a rate you can't imagine. If you were to gently bend a weld between two pliers you'd eventually break it. Band saw blades go through hundreds of such bends every minute. The higher the blade is tensioned the faster they'll break. You can back off the tension or back off the blade guides to solve the breakage problem. I don't let anything deflect my blades nor let the blade flutter enough to run against a blade guide in operation. Band saws are all about blade transport. Operating the saw with the blade not running straight between the wheels creates incredibly tight radius bends where the blade enters at an angle and again when it exits the workpiece, changing direction again to return to the lower wheel. That, alone is two bends. Then add in the bends where the blade leaves and enters the blade guides. So that's four little bends and you only just started! Multiply by 400-500 blade revolutions per minute times 4 occurrences of the half inch radius bend and you're wondering why your blades are breaking?
William, your info seems technically well informed--thanks. If I could distill a bit:
Another thing: let go of the workpiece occasionally to check that the blade is not being deflected. With low tension you might not feel when you're pushing the blade to the left or right as you follow a scribe line forward. I leave enough space between the upper blade guides to see when the blade touches and correct immediately. If the blade isn't touching the blade guide it can't be deflecting (assuming your guides are set to the nominal straight path from top to bottom wheel). If the workpiece is too heavy to slide itself back into alignment you'll have to push it back. So; while you're watching your scribe line with both eyes, keep your third eye on the blade guides. They're not just for twisting the blade into radius cuts, they guide your eye through straight cuts to keep the saw and the workpiece in line with the wheels' path. Watch the space between the blade and the rollers and you won't break as many welds. Keep your tension as low as your tensioning system allows to conserve horsepower.
In my opinion you get what you pay for with these blades and you might want to opt for the more expensive saw blades so you aren't changing them out so often.
There has got to be a better bandsaw blade to use than what you are using currently. Consider Lennox Wood master B. Will last longer.