Remembering to de-tension your bandsaw Blade

[Roger Feeley]

Here's something I did years ago to avoid forgetting to de-tension my bandsaw. I mounted a small microswitch so that the tension lever turned on some work lights when the blade is under tension. The light is not switched with the shop lights. When I leave the shop, I turn off the lights and it's easy to see if the bandsaw blade is under tension. The saw is in sort of a dingy area of the shop so it's easy to remember to tension the blade too. Without the blade under tension, the light's kind of bad.

[Neil Brooks]

What a great idea !

I stuck a label on the upper wheel cover of mine, reading simply "Blade Tension."

I'm very used to seeing the label, so ... half the time, I simply forget.

But it's never cost me any sleep ;)

[John Coloccia]

Hang yOur dust collector remote on the tension lever.

[Roger Feeley]

You want to hear about a really elaborate solution, see my recent post about power indication for a Sawstop. This solution was the inspiration for that one. The idea was to light up a flood light over my Sawstop when the main power is on but the main power is only 20ma.

[Mike Harrison]

...to avoid forgetting to de-tension my bandsaw...

WHY on earth would you do that?????

Whats supposed to happen if you don't de-tension the saw???

Had mine little 14 incher for close to 20 years, put on a riser and 3horse motor and never done that, saws fine.

[Joseph Tarantino]

then i suggest you keep your saw under tension. many of the reputed band saw experts, and most tool manufacturers, recommend detensioning the blade, at least for longish periods of non-use, to prevent flattening of tires and bending the saw frames.

[Roger Feeley]

There are a number of reasons:
1. If you leave the bandsaw under tension for a long time it weakens the tensioning spring. Carter does a nice business selling replacement springs.
2. If you leave the saw under tension, the rubber tires get flat spots and it runs 'bumpy'. combine that with funky springs and things get bad.
3. I don't know if I buy this one but 'they' say that if you leave the bandsaw under tension, it will warp the castings. I choose not to temp the fates.

I can tell you that I have two bandsaws. My old Craftsman has been under tension for 20 years and the spring is shot and it's very hard to get the tension right. I really should put a new spring in it. I can't say if this is because of the constant tension but it doesn't track as well as it used to despite adjustment. Now, it's sort of a cheap saw so maybe the above two reasons apply more to it than to better saws.

My other saw is a 17" Rikon which is the one I have the light on. It's no big deal now to de-tension it because of the reminder.

[Roger Feeley]

I guess I'm just one of those people that can't stand a crooked picture. I see a problem, visualize a solution and then I have to see if I can make it work. My dad suffered from the same condition. He was a tinkerer and his dental office was full of neat little ideas.

[Carl Civitella]

I had my BS for twenty years and do not de-tension the blade. Tires look new yet, no problems with springs, changed the drive belt once on the motor. I use the BS more then any tool in the shop. Things wear from inproper set up and operation mostly. But if i have to buy new tires or springs, well 20 years is a very long time, I got my monies worth out of it. I would not fret over it. Carl

[Roger Feeley]

I have an old craftsman BS and the tires on it definately have flat spots. Also, the spring is shot. I should really replace both because it won't track well any more. I don't use it much because I have a newer Rikon. That's the one I put the work lights on.

[Curt Harms]

I had my BS for twenty years and do not de-tension the blade. Tires look new yet, no problems with springs, changed the drive belt once on the motor. I use the BS more then any tool in the shop. Things wear from inproper set up and operation mostly. But if i have to buy new tires or springs, well 20 years is a very long time, I got my monies worth out of it. I would not fret over it. Carl

I wonder if that's why you don't have problems. I suspect that flat spots on tires and set in belts happens when things don't move for extended periods.

[Chris Fournier]

Be sure to give the tensioning assembly a shot compressed air to clear out the sawdust and then a squirt of dry lube on the threads! There's tons of pressure here and you can wear this assembly out as I did if you're a de-tensioner.

[Mike Harrison]

All these beliefs are simply, Urban Myths.


If you leave the bandsaw under tension for a long time it weakens the tensioning spring....And the springs on your car, they're compressed 24/7?


2. If you leave the saw under tension, the rubber tires get flat spots and it runs 'bumpy'....And the tires on the car?


...but 'they' say that if you leave it under tension, it will warp the castings......ever hear anyone complain about it?

Believe me, I'm not singling you out here, but these statements / claims always come up, and there is no basis in fact to substantiate them.

[Harold Burrell]

I wonder if that's why you don't have problems. I suspect that flat spots on tires and set in belts happens when things don't move for extended periods.

I would expect that would be it exactly.

[Chris Fournier]

The springs on your car are always under the static load of your car certainly but not always under the dynamic loads of driving. Band saw tires are not pneumatic as are car tires. Castings will warp all on their own without any applied loads.

There is plenty of info out there to substantiate the claims/facts that you so easily refute, I'd likely start with metalurgy...

[Jim Davenport]

Being that I'm old and forgetful, I made a sign to remind me.

[Joe Angrisani]

Being that I'm old and forgetful, I made a sign to remind me.

As long as you don't get used to the sign..... :)

[Chip Lindley]

I am not a "detensioner." And, I have never found keeping the blade under tension to be a detriment to the saw. Once my '90s Delta 14" BS is set to saw correctly, nothing is touched until need be. Detensioning causes lots of adjustments to need resetting all over again. Wise or Lazy? You choose!

[Tony Bilello]

When I use my bandsaw regularly, I don't de-tension. When It is going to sit for a while, I will de-tension.

[Joshua Culp]

There is plenty of info out there to substantiate the claims/facts that you so easily refute, I'd likely start with metalurgy...

Metalurgy says that as long as the spring is kept within it's elastic region, and not over stretched into it's plastic region, then it really doesn't matter if it stays tensioned or not. So, as long as a manufacturer designs the saw correctly and uses the correct spring for the application (size, material selection, heat treatment), then the spring doesn't care if you leave it under tension or not.

Anyone who has had a tensioning spring failure most likely stretched it beyond it's intended limit, or the manufacturer used the wrong spring for the application because they were cutting manufacturing costs, or because the engineers just didn't care/know better.

As for car tires, older tires would indeed flat-spot if they sat for as little as a week. Newer car tires are made of improved materials and don't have that problem. I have no idea what materials are used for band saw tires across the brands, so this may be a valid reason to de-tension when not in frequent use.

To me, the biggest reason to de-tension (which I don't do) is to avoid stretching the blade. The blade acts as a big spring, so all the metalurgical properties discussed above in relation to the tensioning spring apply here too. It is very easy to stretch thinner blades into their plastic region without knowing it, and once you've crossed that line, you can never go back - permanent damage is done to the blade and it is weaker and longer. This leads the operator to just keep putting it under more and more tension, wondering the whole time why it isn't staying where he set it. The answer is because the blade keeps stretching over the days/weeks/months, and as the blade gets longer, the tension decreases - so the operator cranks it up again until the blade finally breaks. A quality blade is one that is made of the proper material and heat treatment that it is designed to remain in it's elastic region while subjected to the stretching forces capable of being exerted by the saw it is intended for.

I'm in agreement with the guy who said a few posts ago that there are too many adjustments on a bandsaw that need re-adjusting after re-tensioning the blade, so why de-tension in the first place. Then again, maybe it's just because I have a cheap, old, hand-me-down three-wheel saw that should have been scrapped a decade or two ago.

[george wilson]

I haven't de tensioned my Delta 14" since 1964. It still works fine,doesn't make flat wheel type noises when I start it up,and it sits for long periods between uses. If I de tensioned it,my wife would be certain to start it up when she uses it(at infrequent intervals),and ruin the blade.

[Myk Rian]

Do I de-tension? Nope.

[Chris Rosenberger]

I like to keep thing simple.

For my band saws.

http://i123.photobucket.com/albums/o303/chrisrosenb/20110612_1.jpg

For the dust collection on my planer.

http://i123.photobucket.com/albums/o303/chrisrosenb/20110612_2.jpg

[phil harold]

I had not used my delta bandsaw for multiple months, 6 or more, I did ruin the tires leaving it tensioned for that long with a narrow blade
I did take the tires off and reinstalled them inside out, been good for 3 years now
I did not learn to de-tension the blade from this experience...

[Jeffrey Makiel]

My 18" low quality bandsaw is 22 years old with the old fashion rubber tires. It's never been de-tensioned (other than blade changes) and may sit idle for weeks since it's used for hobby duty. The tires look fine and the saw runs the same as when new. Re-tensioning while changing blades has not been an issue either.

Jeff :)

[Marty Paulus]

I detension but it is a simple lever pull to do so. If I had to spin a knob each time I doubt I would do it.

[Chris Fournier]

Joshua, I agree with your elastic and plastic observations pretty much whole heartedly except in practice I have found that springs "sack out" all too often. I used a heavy blade on my Delta BS, it was within the mfgr's spec but as you pointed out their spring choice was not really up to the task and I replaced a few. I used the saw pretty hard.

Having worked in a performance motorcyle shop and having the ability to measure springs I can tell you that they wear out even if they've only been in the elastic region and I'm talking valve trains and suspension. I would imagine that the suspension springs may have taken a few trips into the plastic region but many older bikes were over sprung and still their springs are shot.

[george wilson]

It may very well depend upon the quality of the steel in the spring. Too low a carbon content to begin with can be a problem. I know that automobile leaf springs can be too soft because I have sawn them into crossbow bows with carbon steel blades without trouble. If they were 1095,they would soon wear the blades out. I was discussing the spring stuff with a gunsmith some time ago. He remarked that there are quite a few 50 round Thompson machine gun magazines that have been wound up full of ammo for 75 years that still work fine. Many 18th.C. guns still work fine,though their lock springs are always under tension.

[David Weaver]

This thread just reminded me that I forgot to detension my bandsaw this weekend. And at the rate I use it, I might not turn it on again in 6 months. Maybe I'll leave it tensioned as an experiment. It'd turn it on a lot more if I didn't have to tension it, as lazy as that sounds, I'd rather just pull a handsaw off a rack, mark a line and cut than tension the bandsaw and screw around with changing blades, etc.

[John Coloccia]

I never detension mine. If I had a 24 hour machine shop, would I have an 8 hour rest period for my bandsaw, where I detensioned it and let it sit?

Springs generally fatigue through cycling, not static load. My guess would be detensioning reduces spring life if anything. I would guess that repeated cycling is probably bad for the blade as well.

[Jeff Monson]

I never detension mine anymore. It has never seemed to make a difference on my tires.

[Ken Fitzgerald]

This subject is one of the most debated/argued subjects here at SMC.

I detension mine. While constant tension may not damage the springs, I believe it does cause the rubber tires to become compressed in a small area and lead to premature wear and tracking problems.

So I detension saw but as David Weaver pointed out, I may go for several months without using my bandsaw but I should be using it later this week.

Frankly, I don't see the big argument against detensioning it. I can retension mine, check it's tracking and be using it in less than 60 seconds. If I'm in the middle of a project where I may be needing my bandsaw again, I will leave it tensioned.


Of course, I don't have a crown on my tires....as they are flat.

Flat vs crowned tires......and I don't glue my tires either....... next battles......:rolleyes:

There is no right or wrong answer IMHO

[george wilson]

Flat spots on tires probably also depends upon the quality of the tire material. I use 1/4" blades on my 1964(purchased used) Delta 14",and never have had a problem with flat spots or grooves in the tires. I think there are too many variables in springs,materials,etc. to give a definitive answer. I just don't want my wife,who doesn't mix with machines well,to start up my slacked off bandsaw and make a mess out of it.

[Neil Brooks]

There is no right or wrong answer IMHO

And I don't happen to think it's any more complicated than that.

At the gym (no, I don't go, but I HAVE gone ;)), there's an unwritten rule: don't correct another person's technique, unless you KNOW it's going to cause them HARM.

I don't care if you de-tension your band saw blade or not. I may voice my opinion, but ... to state it as if it Came Down From The Mountain -- one way or the other -- to me ... well ... I dunno. I don't see the point in it.

[Ken Fitzgerald]

My wife doesn't use power tools so that's not a problem.

George, I am using an Italian made bandsaw and I hope the quality of material is good as I paid for good quality.

One of the biggest problems people have with getting a bandsaw to function correctly deals with proper tensioning of a blade. Too loose well, it'll drift and cut curved surfaces. Too tight?....probably just compress the tires too much and put too much pressure on the smaller parts in the tensioning portion of the machine. I doubt you will see a difference in cut with too much blade tension if all other variables remaining constant. My point is that detensioning takes the pressure of those smaller parts that are in fact, high failure items in bandsaws. I just fail to see how detensioning a bandsaw creates any problems.

But...in the end....I think it's making a mountain out of a mole hill.

I don't think there is a right answer or a wrong answer. Do what's right for you.

I can assure you I will do what I want in my shop.

[Zahid Naqvi]

Tomato/tomato (that doesn't come out right when you write it). My name is Zahid and I am a detensioner :eek:

[Dan Hintz]

This subject is one of the most debated/argued subjects here at SMC.
SawStop... 'nuff said ;)





Car springs go through tension/detension quite a bit (especially with the way I drive). Different alloy, but you get the idea... there's more to this story than any one thing.

[Neil Brooks]

Tomato/tomato (that doesn't come out right when you write it).

LOL ! Yet ... I got it, immediately :D


My name is Zahid and I am a detensioner :eek:

Realizing it ... IS the first step ;)

[Jim Rimmer]

This thread just reminded me that I forgot to detension my bandsaw this weekend.
Yep, me too. Just reading the thread to determine if I need to worry or not. Don't worry wins out. If i don't forget, I'll detension tonight when I get home. :rolleyes:

[Andrew Pitonyak]

All these beliefs are simply, Urban Myths.

...And the springs on your car, they're compressed 24/7?

...And the tires on the car?

...ever hear anyone complain about it?

Believe me, I'm not singling you out here, but these statements / claims always come up, and there is no basis in fact to substantiate them.

Broke a spring on my car once, see.... :D

I was told that if you let a car sit that it is possible to cause problems with the tires. May not be a problem with newer tires. My car never sits long enough for me to worry about it.

[Jerome Hanby]

Just to bring all of this back around to bandsaws, ever see that Mother Earth News project for the bandsaw that used old VW rims and tires for the bandsaw wheels and tires?


Broke a spring on my car once, see.... :D

I was told that if you let a car sit that it is possible to cause problems with the tires. May not be a problem with newer tires. My car never sits long enough for me to worry about it.

[Neil Brooks]

Just to bring all of this back around to bandsaws, ever see that Mother Earth News project for the bandsaw that used old VW rims and tires for the bandsaw wheels and tires?

Somehow ... I'd still predict you'd wind up with an electrical fire on your hands ;)

[Curt Harms]

Just to bring all of this back around to bandsaws, ever see that Mother Earth News project for the bandsaw that used old VW rims and tires for the bandsaw wheels and tires?

I didn't see that but I've seen a web video of a homemade backwoods sawmill where the blade structure was stationary and the log moved. Automobile tires and wheels, small V8 with manual transmission for drive train. Crude but it looked like it worked pretty well.

[Paul Ryan]

My name is Paul and I am not a detensioner.

I honestly think the detensioning levers are more a gimic than any thing. 1st company A did it then companey B felt they needed to. At 1st I bought into the dentensioning myth and tried to remember to do it. Ya right like that was going to happen. And when I did remember to flip the lever. I F'd up a couple of blades because I forgot to retension then. So now I just dont do it and have had no problems with either of my bandsaws. There are times the 14" goes months with out being used, and time the 19" goes months with out use. So I really dont think it is necessary.

[Anthony Whitesell]

All these beliefs are simply, Urban Myths.

...And the springs on your car, they're compressed 24/7?

And after a while the ride height will change. I managed to get a pair of springs for my 2004 Altima cheap (from a totaled wreck) which I put aside to change when I got to my third pair of shocks. I just changed the shocks and springs. What a difference it makes!



...And the tires on the car?

Do you have urethane tires on your car? Nope. Not a true comparison. I will say for your next car try some Polyester based tires. The tune will change. They flat spot in less than 48 hours. I have some on my RV the only vehicle that sits more than 2 days.



...ever hear anyone complain about it?

Believe me, I'm not singling you out here, but these statements / claims always come up, and there is no basis in fact to substantiate them.

I de-tension when I remember. But them I forget to tension before I start the saw. May be I should follow the example of the fellow with the signs over the switches. On the other hand being an engineer, I'd rather have an interlock (switch and relay) that prevents me from turning on the saw when the tension lever is up.

[Harvey Pascoe]

Well, I usually de-tension mine but occasionally forget. I figure its no big deal. But guess what? After three years I wore out the threads in the damn tensioner even though I lube them. Screw that, not gonna do that no more.

Chris, I have some education in metallurgy. Castings do not warp all by themselves, if one ever should then it is defective and I've never heard of such a thing. Iron castings should not even warp under heat and stress or they wouldn't make car engines from iron. The modulus of elasticity of both iron and cast or extruded aluminum is sufficiently great to withstand the rather low loads of a tensioned blade.THE AMOUNT OF STRESS IS INSIGNIFICANT. Cast iron has nearly zero elasticity and breaks before it bends. That is why engine blocks crack with even minute heat distortion. As for the tires, just depends on the quality of the material. As for the springs, any long time saw owner knows the answer to that one, but they weaken whether you relieve them or not due to changing load. They solved that problem with car springs long ago so poor quality springs is the problem with saw springs.

[Dan Hintz]

25k psi sounds like a lot of stress to put on something ;) Just sayin'...

[Harvey Pascoe]

So the bottom line is that there are too many variables, particularly quality, right materials to draw any general conclusions?

As usual, do what works best for you . . .

[John Coloccia]

Well, I usually de-tension mine but occasionally forget. I figure its no big deal. But guess what? After three years I wore out the threads in the damn tensioner even though I lube them. Screw that, not gonna do that no more.

Chris, I have some education in metallurgy. Castings do not warp all by themselves, if one ever should then it is defective and I've never heard of such a thing. Iron castings should not even warp under heat and stress or they wouldn't make car engines from iron. The modulus of elasticity of both iron and cast or extruded aluminum is sufficiently great to withstand the rather low loads of a tensioned blade.THE AMOUNT OF STRESS IS INSIGNIFICANT. Cast iron has nearly zero elasticity and breaks before it bends. That is why engine blocks crack with even minute heat distortion. As for the tires, just depends on the quality of the material. As for the springs, any long time saw owner knows the answer to that one, but they weaken whether you relieve them or not due to changing load. They solved that problem with car springs long ago so poor quality springs is the problem with saw springs.

My bandsaw table is cast. Without the alignment pin, I can easily bend the table by quite a bit. That's just an example and I don't want to belabor this point, but stiff and brittle isn't the first thing that comes to mind when I think about cast iron.

[Harvey Pascoe]

My bandsaw table is cast. Without the alignment pin, I can easily bend the table by quite a bit. That's just an example and I don't want to belabor this point, but stiff and brittle isn't the first thing that comes to mind when I think about cast iron.

John, then they must made it of maleable iron because that's not normal. What's the point of using iron if it bends? I don't even bother with the pin since mine doesn't. Of course, they can cast iron with hundreds of different alloys for various properties and perhaps the standards used for our types of machines aren't so great. But I'd suggest that you never drop a thin casting on concrete floor if you don't think its brittle.

[Chris Fournier]

Perhaps warp is a poor choice of words. While I am not a metalurgist I have taken related courses via my welding/machining activities. I don't think that castings are as stable as you state Harvey due to the very nature of the casting process. The molten casting cools at different rates in different areas where thickness varies. A larger casting can even start to cool in places when its being poured still. All of this creates internal stresses which will create movement in a casting, iron, aluminum etc.. Of course good post casting heat treating is designed to deal with this stress but just as poor castings are designed, there is poor heat treating too and we then have castings that "move".

Cast iron certainly isn't super bendy stuff but bend it does when under load. A classic example if the Bridgeport Milling machine with a 9" by 42" horizontal working surface. On older machines this table droops at the unsupported ends just from its own weight.

How does all of this affect us and our bandsaws? I don't really know but I see no harm in de-tensioning while I see the potential harm in not de-tensioning. I have chosen to take the 20 seconds to de-tension my machine at the end of the day.

[Ken Fitzgerald]

A lot of the major brands have the alignment pin to which John is referring. My Italian made bandsaw has one.

That being said, as Harvey points out, I have dropped cast iron parts onto a concrete floor and had them break.

I don't see any harm in detensioning. In my shop I detension. You don't want to detension, in your shop you can do what you want.

I certainly don't think there is a strong enough argument against it to warrant aguing about it.

[Billy Trinh]

I'd rather replace a tire on purpose than a good blade on accident when forgetting to re-tension :).

[Marvin McConoughey]

You have a valid point. Cars stress their suspension springs for the life of the car and very few have noticeable spring collapse. I have observed some flat spotting on a few brands of tires, but it goes away after a few minutes of driving. Has any long term research been conducted? Anyone?

[Mel Fulks]

In different shops I've only seen one bandsaw that was de tensioned . That was a Wadkin resaw that the boss said was factory specified. The other bandsaws in the same shop were not de tensioned. So now you have ALL the industry facts!

[Bruce Page]

In different shops I've only seen one bandsaw that was de tensioned . That was a Wadkin resaw that the boss said was factory specified. The other bandsaws in the same shop were not de tensioned. So now you have ALL the industry facts!
In almost 40 years of working in various machine shops, I never saw a bandsaw de-tensioned. That said, I do de-tension my MiniMax and my small Rikon. :rolleyes:

[Jim Andrew]

My farm tractors get flat spots on their tires, when I first pull them out and go down the road towards the field, sometimes they bounce for several minutes. And I would never leave a full load on a truck for extended periods.

[Jeff Duncan]

Wow, talk about bringing back an old thread!!!

Might as well ask people what's better chocolate or vanilla, you'll probably get a similar split;)

JeffD

[Ole Anderson]

I just cut a 4x4 square of 1/4" ply and ran a BS kerf half way through, used a marker to say simply "TENSION" on both sides. I leave it in place as though I just cut the kerf. Impossible to miss.

[Bill McNiel]

Well, now that I have a firm understanding of detensioning I think I'll go back to the Shop and get to work.

[Frank Drew]

I'd rather replace a tire on purpose than a good blade on accident when forgetting to re-tension :).

I can't imagine that you've ever replaced band saw tires by yourself, or paid someone else to do it, if you believe that. I mean, how much does a new blade cost? And anyway, de-tension in the evening and re-tension in the morning, like turning the lights off then on, make it a habit like putting on your seatbelt. Not difficult.

I sent my wheels back to Oliver to have the tires replaced, and among their general advice with the return shipment was to slack off the blade daily, so I did. I don't know about the metal issues, but I've seen a lot of band saw tires with grooves worn into them.


Detensioning causes lots of adjustments to need resetting all over again. A well set-up saw shouldn't need multiple adjustments when re-tensioning, or at least mine never did.

[Mel Fulks]

That's useful, Frank . But they could have already told you in the owners manual! Might be one of those things where all manufacturers think detensioning is a good idea but don't want to lose sales by "being more trouble than the one at Harbor Freight"!

[Frank Drew]

Never did have an owner's manual; I believe it was from the 1940s and I bought it around 1981 or 1982.

[Ray Selinger]

I have a 14" Beaver 3300, I think it's either a 1947 or 48, I know it's not a '49. Since '72 I've only detensioned it to change bands. I don't think the previous owners detensioned either.

[Mel Fulks]

Thanks for reply ,Frank. Hope others who have manuals will check and report. I do think that ease of use and low maintenance are now valued above any consideration of longevity and that current marketing and manuals for most goods reflect that. I can remember old car manuals that listed stuff to do every 100,000 miles! Many of us in seeking help from factory reps have heard maintenance tips not found in print.

[Nick Lazz]

Ok, why not?...I'll chime in. I have detensioned because I read that you're supposed to but forget most of the time. I think it probably stretches the blades more than harms the machine and could contribute to blade failure. I've had a blade break in the machine before and it about scared the bejeebus out of me.
That said, I tend to agree it's urban myth...and just had a bad weld on a blade.

[michael langman]

My simplicity snow blower uses 3 or 4 springs under extremely high pressure, and they are never detensioned. I had 1 spring break in 25 years use, and it was very hard to replace, as the tension was so great.
As for valve springs in cars, the steels today are so much better the the steels of yester year. And the heat from the engine is doing more damage to the older springs then the tension under being compressed.
The 14" band saws don't create enough pressure to damage the castings let alone the materials used today for tires.
If I had a carbide blade on a 20 inch band saw I might detension it, as the pressure is a bit higher.
If your stretching a band saw blade by leaving it under tension then I would be using less pressure on that band saw.