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Thread: Why release the tension?

  1. #46
    Join Date
    Mar 2005
    Location
    Cashiers NC
    Posts
    603
    I had a Delta clone that I never released the tension on. My new Laguna has a tension lever. I release it when I shut the shop up for the day. I keep a stick laying on the table that has “tension saw” wrote on it. I tension it and remove the stick before use. I have no idea if it helps but it can’t hurt.
    Charlie Jones

  2. #47
    Why release tension? Simple, to change the blade.

  3. #48
    Join Date
    Dec 2006
    Location
    Toronto Ontario
    Posts
    11,247
    In 40 years in industry I’ve never seen a saw detensioned and do it at home either.

    I have a 90 year old motorcycle and it’s valve springs have never been detensioned.

    I have fathers in metallurgists, they design good alloys......Rod

  4. #49
    Join Date
    Mar 2014
    Location
    Houston, TX
    Posts
    437
    I forgot one time and the blade popped out of the slot next to the on button and cut my finger when I turned it on. It stays tensioned now. No reason not to those tires are cheap and it's easy to put them on.

  5. #50
    Join Date
    Mar 2014
    Location
    Houston, TX
    Posts
    437
    I've never understood why they don't put a removable cover over that slot.

  6. #51
    Quote Originally Posted by Travis Conner View Post
    I've never understood why they don't put a removable cover over that slot.
    That's a good point. It should be easy to do. I'd buy a roll of dry erase magnet "stuff" like this (LINK) and cut it to length/width then overlay the slot.
    "All that is necessary for the triumph of evil is that good men do nothing."

    “If you want to know what a man's like, take a good look at how he treats his inferiors, not his equals.”

  7. #52
    Join Date
    Mar 2014
    Location
    Houston, TX
    Posts
    437
    It took like 4 months for that cut to heal too since it was at the tip of my finger it would constantly reopen the cut when I bent it.

  8. #53
    I got my 14" cast iron Delta new in 1996. It has only been detensioned for blade changes. It works as well today as it did when I bought it 25 years ago. I have never broken a blade; blade changes are have only been because they have gone dull from wear. It gets hobby use, but is used at least once a week on average, though it can go a few weeks during the summer without any use. I did wear out a set of tires on it about 15 years ago. The higher quality replacement tires are still good.

    The machine shop I worked in for 5 years during and after college had two bandsaws, a 36" metal cutting DoAll and a 24" Tannewitz we used for wood and aluminum. Neither were ever detensioned while I worked there, and I have no reason to believe they had ever been detensioned at any time prior or since.
    Last edited by Andrew Seemann; 02-24-2021 at 12:59 AM.

  9. #54
    Join Date
    Feb 2003
    Location
    Doylestown, PA
    Posts
    7,551
    I have a Rikon with a detensioning lever. I'm sure a shop where a bandsaw runs at least once every few days doesn't benefit from detensioning. I haven't turned my saw on for probably 3 months and it takes bout 2 seconds to tension/detension. I unplug and hang the cord over the detensioning handle, haven't started it detensioned yet.

  10. #55
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298

    Tensioning reminder

    I don't see that I posted this in this thread, but for those who detension when planning not to use the saw for a while (as I do) here is an idea for a reminder to retension before turning the saw on. This is not original but I can't remember where I got the idea.

    This board hangs on the wall next to my saw.

    tension.jpg

    JKJ

  11. #56
    Join Date
    May 2009
    Location
    Wenatchee. Wa
    Posts
    769
    Reading through these threads I noticed that no-one ever mentioned that they had experienced flat spots or grooves on their bandsaw tires. Or perhaps as soon as they ran the machine they disappeared. Is it possible that the newer non rubber tires do not take a set and the old ones did? Might be another myth that needs to be laid to rest, kinda like the one about never laying a plane blade down on a wooden surface.
    (Sorry I could not help myself)

  12. #57
    Join Date
    Mar 2014
    Location
    Houston, TX
    Posts
    437
    I put one covering the on off switch and that worked great until a friend moved it and didn't read what it said, so I just leave it tensioned from now on.

  13. #58
    Join Date
    Apr 2020
    Location
    Tennessee
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    I’ve had this question as well. I’ve never de-tensioned my band saw. But I have wondered why the talk about releasing the tension.

    My Grizzly 16” bandsaw is nearly 20 years old and I’ve never had any noticeable affect from leaving it tensioned even after several years of not using it. It has the original tires on it as well.

    If my tires had degraded after 20 years I’d think that is a normal degradation of rubber “dry rot”. But that hasn’t even happened. Also, I kept my blade way over tensioned until recently when a new blade came with an instruction sheet on proper tensioning. It is a lot less tension than I used to keep on it. I used to simply tighten it as tight as I could get it. There are no flat spots or other noticeable issues.

  14. #59
    Join Date
    Nov 2007
    Location
    NW Indiana
    Posts
    3,078
    I have two band saws and only detension when I run very small blades such as 3/16" or less.

  15. #60
    Join Date
    Apr 2020
    Location
    Tennessee
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    451
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    Based on the responses, I'm not seeing any evidence in support of de-tensioning the blades. I would agree that if you're happy with doing it and that de-tensioning on your saw doesn't cause additional issues then it doesn't hurt to do it and errs on the side of caution.

    Scientifically, the question comes down to the response of the materials when put under tension in the saw. I assume most if not all spring mechanisms in these saws are made from coiled spring steel which likely are well within their elastic region and likely to have an equivalent infinite life at the stress values seen by the materials. My saw has shown this to be true with no effect on the springs. It comes to mind that we don't know if a manufacturer may have used cheaper materials or have spring designs that are going beyond their elastic properties.

    The remaining metal components involved include the wheels, bearings, fasteners and frame components. Once again these are expected to be loaded in their elastic region with an expectation of infinite life. Same argument would apply for a manufacturer using a poor design or incorrect materials - they could fail.

    I do think people hear about fatigue failures of springs and such (which can and does happen) but this is a different mechanism and requires repeated cycling. The stress in a bandsaw spring and other tensioned components is a constant while the machine is not in use. When in operation, the bearings, wheels, shafts, and such do have cyclic fatigue effects but this has no impact on de-tensioning while not in use.

    The remaining item would be the rubber tires on the wheels. This can vary and these type materials can creep enough to potentially cause an issue. I own a 20 year old Grizzly and while I'm not so confident the materials chosen for my tires were well engineered (maybe I'm not giving them enough credit - I can't say for certain). But even if it is by luck that my rubber tires are of a material that resists creep or taking a set under the loading presented by my saw, the fact is they have done so very effectively.

    One other item this relates to is the belts, motors, arbors and other related components on all of my machines are all under tension and also have metal and elastomeric materials. However, I don't nor do I see any designs which utilize de-tensioning each time I leave my shop. Granted they do require replacing under heavy use eventually and once again - maybe I've been lucky but I've never replaced a belt on my equipment either. I am a one man shop that took several years off of woodworking while raising our kids and such. My tools aren't used remotely like an industrial/commercial facility. However, my shop represents quite a nice case study of the long term effect of leaving these items under tension.

    My take on this after reviewing this as well as my personal use case is that a well made bandsaw should have no need to be de-tensioned.

    I also know that sometimes even a "well engineered" machine can sometimes have unintended flaws that couldn't have been foreseen initially. So the idea of doing it just in case is still valid. Certainly, if you have a saw that exhibited an issue from being tensioned then by all means do what you need to do for it.

    It really appears to be riskier to de-tension and possibly start it up this way or to tension it incorrectly. It also seems to like it could add additional wear on components that (at least in my saw's design case) aren't designed for repeated tensioning/de-tensioning.

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