De-tension bandsaw blades when not in use?

[Jiggy Joiner]

We have two commercial bandsaws and a heavy duty pro model. All three are from different manufacturers, and all the user manuals recommend slackening the blade off at the end of each working day.
Ours just have levers, and fine adjustment, so tensioning and de tensioning is a slight turn of a lever.
As I mentioned, we have warning stickers at the on/off switches, so nobody forgets.
I slacken the blades off out of habit, as it was how I was taught years ago.

Each to their own I guess.

 

[junk731]

Well you are either the sheep, the dog or sheep herder. Your choice. Some old info we were taught is just that, and it just keeps getting passed forward like gospel.

 

[ScotF]

I do - to prevent issues with the tires. It is simple on mine to unscrew the tension wheel to the right tension. If you are using daily then this would be less of an issue.

 

[Df1k1]

Laguna bandsaw owner. I always de-tension then leave the door open as a reminder to re-tension the blade. Not sure if it makes a difference but I would rather err on the side of caution. There certainly is nothing wrong with reducing the tension but there may (or may not) be an issue with tension 24/7.
Same reason I always unlock the tension on my fence on my saw stop.  Heck, probably doesn’t make a difference but I feel better

 

[ChuckM]

Laguna bandsaw owner. I always de-tension then leave the door open as a reminder to re-tension the blade.
Snip

Now, that's clever.

Snip
Same reason I always unlock the tension on my fence on my saw stop. 

I know of no table saw users who intentionally leave their saw fences in tension. Some probably forgot to release the lever after making the last cut.

A Rikon 14" bandsaw product description I came across includes this: "...a release lever lets you instantly loosen blade tension to prevent premature blade fatigue and wear to the saw's bearings, tires and spring." Myth or truth (or sales pitch)? Your call.

 

[Bob D.]

I release tension as I said on my bandsaws, but thinking back I worked in a pipe fab shop for many years and we never de-tensioned the blades on those bandsaws. We had a couple Marvel tilt head vertical bandsaws, I don't remember the particular model but it doesn't matter, we cut 16" WF beams, pipe, and all sorts of steel with them but never released the tension at the end of the day. Didn't seem to bother them one bit.

I do it on my wood bandsaws because that's what the manual advises. It takes only a second but YES it does open you up to the possibility of starting the saw with the blade de-tensioned. Like every other tool in your shop you have to engage your brain first, then proceed to operate the tool which includes ensuring the blade is clear of any obstruction and ready for action.

And yes, I did once screw up and start my 12" bandsaw without checking the tension. Ate the tire on the upper wheel and destroyed the blade. Lesson learned and 15 years later no repeats.

 

[Cheese]

...but thinking back I worked in a pipe fab shop for many years and we never de-tensioned the blades on those bandsaws. We had a couple Marvel tilt head vertical bandsaws, I don't remember the particular model but it doesn't matter, we cut 16" WF beams, pipe, and all sorts of steel with them but never released the tension at the end of the day. Didn't seem to bother them one bit.

Good point Bob, thinking back over the years in the machine shops and the engineering model shops, metal cutting band saws were never, ever de-tensioned. The only time the blade tension was released is when the saw blade broke.  [tongue]

 

[WarnerConstCo.]

Big difference between a real industrial cast iron saw, with large bearings and large spindles.

These welded steel saws with small arbors and small bearings wont last as long and the manufacturer knows that tension will decrease that time even more before components fail.

It's how they cya. 

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[ChuckM]

If detensioning were indeed meaningless, shouldn't at least one bandsaw manufacturer seize the opportunity and release a bandsaw model that promoted "detension or retension totally not required" as its a selling point?

 

[Svar]

Manufacturers that recommend de-tensioning should be adding auto switch. You can't start the saw unless it is tensioned. One could probably DIY it too.

 

[WarnerConstCo.]

If detensioning were indeed meaningless, shouldn't at least one bandsaw manufacturer seize the opportunity and release a bandsaw model that promoted "detension or retension totally not required" as its a selling point?

Last time I checked, Northfield never mentioned it in their bandsaw literature, but I also don't think anyone here is paying 30k for a new 36" saw.

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[ChuckM]

Manufacturers that recommend de-tensioning should be adding auto switch. You can't start the saw unless it is tensioned. One could probably DIY it too.

I have a Craftsman router. Before I can turn on the router, I need to push the lock button out.

 

[Jiggy Joiner]

Well you are either the sheep, the dog or sheep herder. Your choice. Some old info we were taught is just that, and it just keeps getting passed forward like gospel.

I figure that the people who built the machines, know a bit more about them than I do.
So when I’m handing over big sums of money, for machinery, I want it to last. So following warnings and advice that they put in the manuals, makes good sense to me.

All of my petrol power tools, mower, chain saws, brush cutters etc, state not to leave gasoline in the tanks for lengthy periods. So I empty them if they’re not used for a while.
Just another example of taking heed of the manual.

 

[Kevin D.]

I have a Delta 14" bandsaw with extension.  I do not de-tension the blades, except with I am changing the blades. 

Doesn't seem to have harmed it in the 25 years I have owned it

Bob

Ditto here except mine is only 18 years old.  It can even sit unused for many months at a time.  Never had a problem.

 

[cpw]

I usually detension, unless I forget.  I have an MM16; so a similar class of bandsaw and always keep my 1" blade on it.  Whenever I detension (it is the wheel, not the lever); I open up the top door's lock.  This disengages the micro switch, so the saw can not be started until I close the door; which reminds me to tension the blade.

 

[Bob D.]

Manufacturers that recommend de-tensioning should be adding auto switch. You can't start the saw unless it is tensioned. One could probably DIY it too.

I've thought about doing that. Doesn't seem too complicated to implement.

 

[WarnerConstCo.]

Manufacturers that recommend de-tensioning should be adding auto switch. You can't start the saw unless it is tensioned. One could probably DIY it too.

I've thought about doing that. Doesn't seem too complicated to implement.

Just a limit switch. My 36" fay and egan 950 has one on the top tension assembly. It's more the shut machine off if a blade breaks though.

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[DeformedTree]

This makes little sense.

When the blade is tight, it has a load in it.  Just sitting there nothing will change. The blade is not going to stretch just sitting there, if it could, the blade would just fail in use very quickly. The blade has to have the tensile strength the handle the load when tension. Just sitting there won't change anything, the load isn't changing or going over the limit of the blade. No different than a torqued bolt, it has to be strong enough for the pre-load, it won't suddenly snap/stretch just sitting there.  When cutting, the blade will warm, thus get bigger thus get less tight, when it cools back to ambient temp, it will be back to it's normal tension.

Now if the concern is your shop changing temperature when sitting there, maybe, but since blade and saw are all steel, they will largely expand and contract as one.

I've never heard of people doing this, it comes across as just plain dangerous as others have mentioned. If there was a real concern the bandsaws would have an auto-tensioner type device just like belt drives and such. It could always limit the tension in the blade. Plus interlocks like Svar mentions.

Far as shafts and bearings.  They too have to handle the static load of the tension, once they are designed for that, just sitting there loaded won't change a thing. If it did change sitting there, the bearings and shafts would again fail right away.

The saw has to be able to handle the loads the blade sees in use, this is going to be higher than just sitting there.

Maybe there is a concern about deforming a tire in one spot, but again, that sounds unlikely. Maybe there is a concern about parts rusting together just sitting there for long periods of time.

Look around us, everything is under load.  We don't unload the stuff around us. It all either handles the load indefinitely, or it fails right away.  Cycle life can come into play and that is what wears out a machine, but obviously that is when it's running, not just sitting there.

This might be a way to use fear to cause folks to regularly check their blade tension.

 

[Jiggy Joiner]

I don’t know if it matters or not, I slacken the blades usually at the end of the day. It takes seconds, to slacken or tension, so certainly not a problem.

If it doesn’t matter, why do all the manufacturers instruct owners to carry out the procedure in the user manuals?

I’m pretty sure a slackened blade is going to cause zero issues in that state, I can’t imagine the same can be said for a tensioned blade, no matter how minimal?

I even know of a cabinet maker that slackens coping, and fret saw blades when not in use.

 

[WarnerConstCo.]

I don’t know if it matters or not, I slacken the blades usually at the end of the day. It takes seconds, to slacken or tension, so certainly not a problem.

If it doesn’t matter, why do all the manufacturers instruct owners to carry out the procedure in the user manuals?

I’m pretty sure a slackened blade is going to cause zero issues in that state, I can’t imagine the same can be said for a tensioned blade, no matter how minimal?

I even know of a cabinet maker that slackens coping, and fret saw blades when not in use.

The manufacturers that state this practice, like I said previously, are the ones that build light weight welded steel saws.

They are probably well aware the components will wear out faster. 

No where, in any literature did Yates American say to detension this saw.

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