Bandsaw Blade Tension

[Chris Parks]

I can recall reading a post where there was a very in depth and quite technical report on BS tension done using different methods including blade stretch. Can anyone point me in the right direction to read it. Thanks.

[Phil Thien]

There have been a few, one is here:

http://woodgears.ca/bandsaw/tension.html

I have tried this and had trouble with getting repeating results. That is, a blade tensioned in this manner 2-3 times in a row doesn't seem to require the same # of turns of my tension knob, and when the blade is plucked, produced a different frequency each time.

But give it a shot, many people have had tremendous success with it.

[Chris Parks]

Thanks Phil, interesting in that it measures blade stretch but not the one I am thinking of. I am sure Mark Dujinski was involved and he recruited someone else to do some testing. I find it interesting when I search for "Dujinski" I get zero hits as I have seen his name mentioned here previously though not often. IIRC he had problems here but I find it strange that his name gets no result.

[Dennis McDonaugh]

I think there is a Z and not a J in his name. I was perusing the old posts and found a very active thread about an article he wrote for a magazine about band saw tensioning.

[David Hawxhurst]

the correct spelling is Duginske.

[Jeff Bartley]

That's a cool article Phil! Chris, I know this wasn't really your question exactly but with my 14" cheap bandsaw I just use the 'flutter' method to tension the blade. Are you trying to tension a large or small saw?

[Erik Loza]

My "method" has been to find the least amount of tension needed to get the cut I want, regardless of blade.

Erik Loza
Minimax USA

[Jeff Bartley]

Erik,
Does the 'flutter' method work for large saws/blades? I have this mental image of a 1" blade fluttering and it's a little scary.

[Phil Thien]

Thanks Phil, interesting in that it measures blade stretch but not the one I am thinking of. I am sure Mark Dujinski was involved and he recruited someone else to do some testing. I find it interesting when I search for "Dujinski" I get zero hits as I have seen his name mentioned here previously though not often. IIRC he had problems here but I find it strange that his name gets no result.

Oh, I think this is the thread to white you're referring:

http://www.sawmillcreek.org/showthread.php?50949-Carter-Iturra-Lenox-Starrett-Comparison&highlight=

A good read.

[Keith Hankins]

Erik,
Does the 'flutter' method work for large saws/blades? I have this mental image of a 1" blade fluttering and it's a little scary.

nope no issue. I use the flutter method on all blades. My Griz 17" HD has a 1" Laguna carbide blade on it. Used that method to put it on and no issues. It's not slapping back and forth, but you can notice (see) the vibration in the blade. When you hit the sweet spot, it's dead still when running. I've never taken more than a minute to put a blade on. I'm with Erik. Least amount of tension to do the job.

[John Coloccia]

Ditto. The flutter method always works well for me, and gets the blade to a point where there are no resonances going on. It's all I ever use.

[Erik Loza]

Erik,
Does the 'flutter' method work for large saws/blades? I have this mental image of a 1" blade fluttering and it's a little scary.

Sure, any blade. Personally, I don't use a hand-held tension gauge. Just play around with the blade, do some test cuts, and see what it wants to do. It will require a lot less tension to rip some 6/4 stock than it would to cut a 12" tall veneer with the same blade, so just find what works. In other words, you probably don't need to be tensioning a carbide blade to 30K psi every time.

Just my 2-cents as always,

Erik Loza
Minimax USA

[mike holden]

Thanks Phil, interesting in that it measures blade stretch but not the one I am thinking of. I am sure Mark Dujinski was involved and he recruited someone else to do some testing. I find it interesting when I search for "Dujinski" I get zero hits as I have seen his name mentioned here previously though not often. IIRC he had problems here but I find it strange that his name gets no result.

I believe his name is spelled: DUGINSKE

Mike

[Dennis McDonaugh]

Oh, I think this is the thread to white you're referring:

http://www.sawmillcreek.org/showthread.php?50949-Carter-Iturra-Lenox-Starrett-Comparison&highlight=

A good read.

He said he was going to do a test, but I couldn't find the results in a thread.

[Tai Fu]

I don't know if this works, but I really do not feel the tension by stretch is repeatable at all. I mean, I clamped a dial caliper across 2 points 5 inches apart, and measured the stretch. On the 1/4" carbon steel blade I'm getting well over .01" of stretch, meaning it should be 30,000 psi (and carbon blades aren't supposed to be tensioned that hard), while on the Woodmaster CT it is as tight as I can possibly make it (you couldn't deflect it at all, even with the guide 12" from the table) the stretch is still under .001". It has proven too unreliable for it to work. A possible reason might be different grades of steel used in various bands, having different young's modulus.

Maybe a more accurate way is putting a load cell or force gauge on the square nut that bears the force of blade tension, to directly measure the amount of pounds that is pressing against it. Perhaps that would be more repeatable and instead of saying xxx psi, just say how many pounds of force is required to bring the tension of say Woodmaster CT to its recommended tension.

[Alan Schaffter]

I still stand by my remarks from that thread!

I contacted Mark via PM but never got a response to my basic question that was also mentioned by a few others, "Where/how do the manufacturers come up with a blade tension?"

I still maintain there is no purely metallurgical/mathematical way to go from blade metallurgy to "the best tension setting" for a particular blade and wood. I don't remember if I posted it or just put it in my PM, but I suspect the way (the only way) you can make the leap to "best tension setting" is by actual testing using bandsaw(s), operated by real people, with real wood- 5 to 10 guys making test cuts at various blade tensions, then either using a simple average or some mathematical analysis tool, to come up with a recommended setting that is "the best" for that blade. So what we have is a precise number generated by an imprecise and very subjective process. Is that any better than the saw manufacturer's (starting point) tension mark?

The only benefit I see to a having a "precise" AND "precisely repeatable" tension gauge (both are important) is when you have already manually determined the best tension setting for "that blade," in "that wood," on "that machine," by using the flutter test or some other method that appears to you to yield a good cut, you can write down that setting. Then if/when you duplicate a cut in "that wood" (same thickness and hardness), using "that blade" (same sharpness) and "that saw", you can save a few seconds by dialing the the previous setting. Of course all that depends on the conditions being exactly the same.

[Chris Parks]

I believe his name is spelled: DUGINSKE

Mike

Mike, thanks for the correction, no wonder I found nothing, I did a web search and that was how the I found it spelled.

[Pat Barry]

nope no issue. I use the flutter method on all blades. My Griz 17" HD has a 1" Laguna carbide blade on it. Used that method to put it on and no issues. It's not slapping back and forth, but you can notice (see) the vibration in the blade. When you hit the sweet spot, it's dead still when running. I've never taken more than a minute to put a blade on. I'm with Erik. Least amount of tension to do the job.
Can you or someone please describe the 'flutter' method and how it is used?

[Alan Bienlein]

Can you or someone please describe the 'flutter' method and how it is used?

Not only that but which flutter are we suppose to use as I can have a stable blade and get it to flutter. When I crank up the tension the flutter will go away but if you go just a hair to far it will flutter again and if you apply even more tension that flutter will also disappear.

[John Coloccia]

Not only that but which flutter are we suppose to use as I can have a stable blade and get it to flutter. When I crank up the tension the flutter will go away but if you go just a hair to far it will flutter again and if you apply even more tension that flutter will also disappear.

First one. You want the blade to be tensioned enough to do it's job, but you also want to get rid of resonances. Flutter method seems to get the blade in a very usable state without any hand wringing. It's not a hard and fast rule, but it mostly works pretty darn well. The evidence is it takes me all of 5 minutes to change a blade, track it, tension it, and set the guides, and it always cuts well right from the start.