Sawmills and Sawing > Bandsaw Mills
Bandmill Blades Breaking
HaroldCR - AKA Fla.-Deadheader:
This might be rehashing old info and ideas, but, it seems to be a constant subject.
It seems that WoodMizer is one company in particular that sets the blade tension really high/tight/whatever you choose to call it. Among other things, it results in loosing pressure in the hydraulic tensioner over time.
We built a homebrew version of WoodMizer design, using trailer wheels/tires. Believe me, we never put the strain on our blades that WM recommends. We cut many thousands of bd/ft of sand laced river recovered Cypress, along with SYP, Live Oak, (harder than any Oak-Hickory y\all are used to cutting), along with several species of Tropical hardwoods, again, harder than y'all cut.
Choice of blades varies greatly, but, we chose the Swedish Steel blades, Munksforsager, and they cut everything we tried. We cut as smooth and accurate lumber as any mill out there.
My theory is, a lot of sawyers run their blades under too much tension. I also believe proper tuning of the mill will allow less tension to be required.
When someone buys a mill, they follow instructions which might appear a little foggy to the buyer. Building a mill, you become one with the mill, and recognize any intricacies with the parts/setup required to properly adjust everything to it's finite potential.
Lately, as I more frequent the forum, I still read posts about blades breaking, especially at the weld. We used to eventually grind the blades down to where the gullets would chatter on the guide rollers. We broke less than 5 blades total, and 3 of those were from jamming and straightening out the kinks.
I am nearly finished with building another WM type design using motorcycle alloy wheels. Having no access to a metal lathe or similar precision tools, this will be a unique situation, to say the least.
I already bought some Munks blades. They are still very reasonably priced. I bought a few for a local saw team to try, and, I just bought more for them, because they were AMAZED at how much better/longer lasting they are, compared to what is sold down here. I need to get them to sharpen their own blades, because here, they just set and grind away, wearing down blades WAY too quickly.
Another local had problems with his blades wandering in the cut. I went to his house and watched him sharpen a blade. I stopped him before he got to the tenth tooth. I changed his tooth angle a little, and ground his cutting wheel to a slightly more rounded gullet, (another reason for blade s breaking, that sharp squared area at the beginning of the gullet) and sharpened the blade. Then, he went to the mill and he started sawing. Less than 3 steps into the cut, he turned and had a large smile on his face. The mill was practically sawing by itself. He is waiting for new blades from me, right now.
Hopefully, my crate will be here by the end of February, so I can get to logging and sawing of our plantation trees, and taking orders for Munks blades and building sharpeners.
Anyone that wants to add to this thread with ideas and experience, feel free, though, keep it civil. The idea of this thread is to enlighten newer sawyers especially, that ALL info may not be right for your mill, according to the manufacturers specs.
I am NOT a mechanical engineer, trained machinist, rocket scientist or anything other than one that pays particular attention to detail. I firmly believe this is most of the problems that develop into excessive blade breakage.
Harold
furu:
Harold
What kind of tension are you running? More precisely how many tensile pounds or newtons in your part of the world are you using? If you have/use a tension meter.
I know that TK recently upped a bit, their recommended tension on their blades (measured on their pressure gauge which is not a tensiometer).
HaroldCR - AKA Fla.-Deadheader:
We used a 3/8" ratchet that tightened the tension bolt, until it got tight, then, engaged the drive belt and watched where the blade ran on the guide rollers. We could change the tracking of the blade with more or less pressure on the blade tension bolt.
Also, we ran on the middle tread rib on the tires, and, that had a little give, also, being a rubber strip.
I just don't see all that much tension being necessary.
More than anything 1/8 to 3/16 down pressure on the blade guides will hold the blade steady, IF you set and sharpen correctly. I can't imaging solid block type blade guides not causing problems heating the blade from friction.
bandmiller2:
Harold, I agree with you on excessive band tension. I built my bandmill about 12 years ago and have never had a band break. Too much tension is an attempt to force the band to cut straight and it doesn't work, its sharp and proper even set that cuts straight. I ran a WM LT-70 for a couple of years for a friend usually after the third sharpening, Bam band breaks and we all jump. My own mill with much less tension I get at least a dozen sharpenings. Frank C.
backwoods sawyer:
Here is what I have.
Been running wm blades, for the most part, for ten years now I have been getting multiple sharpening out of the saws until the last four boxes. This last box 7 have broke on the first run with one still on the mill and one still in the box. I have been saving the ones that look like they can be welded for a slow day.
When all this started WM belts started separating so I changed over to the orange rubber belts, the saws continued to brake and eat up the orange belts, so went back to wm belts, lost a drive belt to a broken saw the other day.
Checked mill for vibration all checks passed!!!
For several years now I have run 80 psi in the air bag style tensioner, up from 60 psi in the manual.
The saws are not all cracked up like a vibration issue they just brake so my thought is that the source of the metal for the wm bands may not be the same mix as it was before the down turn in the economy, same thing with the glue used to hold the outer layer of the belts, less or different glue.
Time for me to try new brands and see if that resolves it, but trying new saws is a hit and miss process I find Suffolk's to be to soft and not hold set and Cooks to be to hard and they don't carry .055.
Navigation
[0] Message Index
[#] Next page
Go to full version