Author Topic: De-tension bandsaw blades when not in use?  (Read 2338 times)

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Online WarnerConstCo.

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    • Warner Mill Works
Re: De-tension bandsaw blades when not in use?
« Reply #30 on: February 22, 2020, 03:17 PM »
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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Offline ChuckM

  • Posts: 1553
Re: De-tension bandsaw blades when not in use?
« Reply #31 on: February 22, 2020, 03:59 PM »
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.
« Last Edit: February 22, 2020, 04:12 PM by ChuckM »

Online Jiggy Joiner

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Re: De-tension bandsaw blades when not in use?
« Reply #32 on: February 22, 2020, 04:57 PM »
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.

Offline Kevin D.

  • Posts: 967
Re: De-tension bandsaw blades when not in use?
« Reply #33 on: February 22, 2020, 06:48 PM »
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.
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Offline cpw

  • Posts: 181
Re: De-tension bandsaw blades when not in use?
« Reply #34 on: February 23, 2020, 09:41 AM »
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.

Offline Bob D.

  • Posts: 1571
Re: De-tension bandsaw blades when not in use?
« Reply #35 on: February 23, 2020, 10:00 PM »
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.
-----
It's a table saw, do you know where your fingers are?

Online WarnerConstCo.

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    • Warner Mill Works
Re: De-tension bandsaw blades when not in use?
« Reply #36 on: February 23, 2020, 10:15 PM »
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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Offline DeformedTree

  • Posts: 698
Re: De-tension bandsaw blades when not in use?
« Reply #37 on: February 24, 2020, 02:30 AM »
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.

Online Jiggy Joiner

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Re: De-tension bandsaw blades when not in use?
« Reply #38 on: February 24, 2020, 08:26 AM »
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.

Online WarnerConstCo.

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    • Warner Mill Works
Re: De-tension bandsaw blades when not in use?
« Reply #39 on: February 24, 2020, 08:34 AM »
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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Offline ChuckM

  • Posts: 1553
Re: De-tension bandsaw blades when not in use?
« Reply #40 on: February 24, 2020, 08:49 AM »
Snip

I even know of a cabinet maker that slackens coping, and fret saw blades when not in use.
I'm one of them, with my Knew fret saw (for a good reason: it uses screw friction to hold the tensioned blade in place, and you don't want those screws worn out prematurely)! ;)

As I said, small or hobbyist bandsaws and narrow blades should deserve different considerations, and I'm not surprised that industrial type or huge bandsaws (metal or woodworking) may have different maintenance needs, just like a mining truck may be serviced and maintained differently from a SUV.

As I dug a little more on this topic online, I found many better known and seasoned woodworkers splitting on this issue as well, although I have yet to find any published materials (books or magazines or manuals) that suggest detensioning is unnecessary for any non-industrial bandsaws intended for hobbyists. Perhaps someone should do so, offering their reasoning and research data to support it.

I found someone quoting online a sawblade maker (Timber Wolf blades) saying this:

   Suffolk Machinery----

"You are somewhat correct. We do recommend de-tensioning to reduce stress on the saw but more so to reduce stress on the blade. De-tensioning is more critical to narrower blades than wider blades although tension/strain is relative to the size of the blade and sawing application. We run as much as 37,500 psi on wider blades such as our 2" x .052 thick blade vs. 9,000 psi on a 1/4" blade. Therefore, we recommend it on all blades. "

Since everyone on either side is happy with what they've been doing, they should keep their practice.

Edit: Mark Duginske (who also patented the cool blocks, among other things) has this to say in his book (2007, 2014): "Releasing the tension is good for extending blade and tire life, though, contrary to popular misconception, it has no effect on the spring...."
« Last Edit: February 24, 2020, 09:25 AM by ChuckM »

Offline grbmds

  • Posts: 1976
Re: De-tension bandsaw blades when not in use?
« Reply #41 on: February 24, 2020, 09:47 AM »
Yesterday I asked Alex Snodgrass (Carter Products) whether taking the tension off the blade is recommended or not. I consider his recommendations valid. He responded that he does take tension off at the end of each day, but it was to avoid flat spots on the bandsaw tires and not related to the blade. Since there are potential flat spots, especially at the top and bottom, more vibration is likely when the saw is turned on the next time. However, after the tires warm up, the flat spots disappear and the vibration disappears. No permanent damage to either the blade, the wheels, or the tires, results. I'm sure everyone will continue to do whatever they have been doing, but keeping tension on doesn't appear to be a practice which causes any permanent problems. That has been my experience also.
Randy

Offline ChuckM

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Re: De-tension bandsaw blades when not in use?
« Reply #42 on: February 24, 2020, 09:58 AM »
Interesting that you mentioned Alex who does the Bandsaw Clinic in the Woodworking Shows (for over 15 years?). He is on record to have said (check out one of the youtube videos) to the effect that no one knows a bandsaw better than its manufacturer. At the request of Chuck Bender, he recently installed, among other items, a quick-release tensioner in Chuck's Delta bandsaw. Chuck's video shows his step-by-step process.
« Last Edit: February 24, 2020, 10:03 AM by ChuckM »

Online Jiggy Joiner

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Re: De-tension bandsaw blades when not in use?
« Reply #43 on: February 24, 2020, 10:06 AM »
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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My machines are commercial, and a heavy duty pro model, they are by no means lightweight. All built in the UK.

From other posts here, it’s clear to me, that slackening a blade, is doing less harm than tensioning one does. It doesn’t matter how big or small the difference, the warnings are there in the manuals, from lightweight to big heavy cast machines. Often the warnings are accompanied by an explanation, stating why this practice is recommended.

Everybody is free to make their own decisions, over many years, I’ve found that reading the actual manual is a wise decision, and taking heed of it is also good advice.
I’ll carry on de tensioning, as the benefits outweigh the negatives (in my opinion)

Online WarnerConstCo.

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    • Warner Mill Works
Re: De-tension bandsaw blades when not in use?
« Reply #44 on: February 24, 2020, 10:08 AM »
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.


Sent from my SM-N960U using Tapatalk


My machines are commercial, and a heavy duty pro model, they are by no means lightweight. All built in the UK.

From other posts here, it’s clear to me, that slackening a blade, is doing less harm than tensioning one does. It doesn’t matter how big or small the difference, the warnings are there in the manuals, from lightweight to big heavy cast machines. Often the warnings are accompanied by an explanation, stating why this practice is recommended.

Everybody is free to make their own decisions, over many years, I’ve found that reading the actual manual is a wise decision, and taking heed of it is also good advice.
I’ll carry on de tensioning, as the benefits outweigh the negatives (in my opinion)
But they are probably welded steel construction with small arbors and bearings?

Not in any manual or literature on any American made bandsaw since about 1880, earliest machinery catalog I own.


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« Last Edit: February 24, 2020, 10:32 AM by WarnerConstCo. »

Online Jiggy Joiner

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Re: De-tension bandsaw blades when not in use?
« Reply #45 on: February 24, 2020, 10:11 AM »
Interesting that you mentioned Alex who does the Bandsaw Clinic in the Woodworking Shows (for over 15 years?). He is on record to have said (check out one of the youtube videos) to the effect that no one knows a bandsaw better than its manufacturer. At the request of Chuck Bender, he recently installed, among other items, a quick-release tensioner in Chuck's Delta bandsaw. Chuck's video shows his step-by-step process.

Exactly, as I mentioned earlier, the manufacturers know the machines they build, better than us.
Why would we have reason to believe their advice is nonsense, or doesn’t really matter?

Offline mattbyington

  • Posts: 458
Re: De-tension bandsaw blades when not in use?
« Reply #46 on: February 24, 2020, 11:49 AM »
Wow, thank you everyone for such an interesting discussion. I've read everyone's comments, some real great tips in there. I really appreciate everyone's point of view.

Matt

Offline Oldwood

  • Posts: 397
  • Alberta, Canada
Re: De-tension bandsaw blades when not in use?
« Reply #47 on: February 24, 2020, 12:59 PM »
Another factor is the diameter of the wheels. The 20 to 36" wheels don't stress the band like the 12 to 16" saws do. This stress causes fractures in the gullets of the teeth.

The bandsaws I have owned are a 36" and 24" both big heavy saws and I never detensioned the blade.

I don' think the saws like Darcey owns are going to have a problem and the large wheels cause very little stress on the bands.
Real knowledge is to know the extent of one's ignorance.
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Offline kcufstoidi

  • Posts: 877
Re: De-tension bandsaw blades when not in use?
« Reply #48 on: February 24, 2020, 01:20 PM »
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.


Sent from my SM-N960U using Tapatalk


My machines are commercial, and a heavy duty pro model, they are by no means lightweight. All built in the UK.

From other posts here, it’s clear to me, that slackening a blade, is doing less harm than tensioning one does. It doesn’t matter how big or small the difference, the warnings are there in the manuals, from lightweight to big heavy cast machines. Often the warnings are accompanied by an explanation, stating why this practice is recommended.

Everybody is free to make their own decisions, over many years, I’ve found that reading the actual manual is a wise decision, and taking heed of it is also good advice.
I’ll carry on de tensioning, as the benefits outweigh the negatives (in my opinion)

Curious as what what Bandsaws are still made in the UK or are we talking about vintage stuff like Wadkins.

Online Jiggy Joiner

  • Posts: 961
Re: De-tension bandsaw blades when not in use?
« Reply #49 on: February 24, 2020, 01:45 PM »
I don’t know which UK companies still make band saws nowadays, as most are gone.

Ours are old but not vintage, well not 1880 anyway.

We’ve got two from Wadkins, and the other is either Start Rite, or Meddings.

Offline Bob D.

  • Posts: 1571
Re: De-tension bandsaw blades when not in use?
« Reply #50 on: February 25, 2020, 06:42 AM »
The attached are from old Rockwell/Delta Bandsaw manuals, one for a 1946 14" model and the other for a 1964 20" Metal/Wood bandsaw.

Both recommend detensioning the blade when not in use.

-----
It's a table saw, do you know where your fingers are?