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Thread: Bandsaw tensioning redux

  1. #1
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    Bandsaw tensioning redux

    I've plowed my way through more than I ever wanted to know on the topic.. (eg https://sawmillcreek.org/showthread....mparison/page7) as well as later threads.

    On my little bandsaw I can twang on the blade and guess that the tension will be about right for what I want to do. My problem comes with my new-to-me Centauro-made MM20 with the broken tension gauge. It looks like replacing the factory gauge involves some fairly major disassembly of a saw that is otherwise working perfectly. -- and then, per the myriad earlier discussions of built in spring gauges, may not be particularly accurate or reproducible.

    I thought that a third party gauge might make it easy to set the blade with some reproducibility. I don't care that much about "real" accuracy, I'd just like to be able to consistently get the same tension in the correct ballpark. With the enormous resaw blade in the saw now my "by feel" methodology is failing me-- I can push it or twang it, adjust the tension by two full turns and feel no difference-- it's just stiff, no matter what.

    So, per the earlier thread from a 15 years ago-- Carter, Iturra Lenox Starrett -- it looks like the Carter is no longer sold, can't find it on their web site. I tried to contact Iturra a couple months ago for a different part and had no response to email or phone calls, so are they out of business? EZTension won't work on blades this large. That leaves Lenox and Starrett. Does it matter between them? A Starrett seems to cost a couple hundred more, it that just inflation due to the name?

    Is there a better way that doesn't involve spending hundreds of dollars? I'm not interested in building a DIY device, I just want a quick check to tell me that my tension is in the right ball park-- that I'm not cranking it down so hard I'm in danger of breaking something.

    Or is it worthwhile to tear the saw apart and replace the OEM gauge (assuming the part is available) instead?

  2. #2
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    Roger ,I bought a tension gauge from a guy on The auction site. Custom machined with a table engraved on the back for tensions/per deflection measured ,with a Mitoyu gage. There are other ways to get to this. John Teneck (I know I screwed up the spelling ,sorry John) on this forum posted his device to tension. If I had not already bought one I would have used John's design. All a tension gauge does is measure the elongation of the blade as it is tensioned. I believe there is a tension gauge device in John Whites book "Care and repair of shop machines" as well ,but it has been awhile since I have looked at the book.

  3. #3
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    From past experience and from the advice of people smarter than me, I'm convinced, as you read, that the gauges on the bandsaws are NOT useful. Some say that without other means, setting it to the next highest mark might work (e.g., set to 3/4" mark for a 1/2" blade.) On my 18" Rikon I have to set it to nearly the mark for a 1" to get the tension I want for a 1/2" Lenox blade as measured by the gauge. I use the gauge only when switching to a new blade then make a note of the indicator position on the saw for future blade changes.

    I bought a Starrett years ago before the price skyrocketed. All of these gauges are the same - a dial indicator, a lever that moves, and two places to clamp to the blade - one on the fixed body of the gauge and the other on the spring-loaded pivoting arm. The gauge is clamped to the blade with tension released then the tension is increased. The gauge simply measures the stretch in the blade when tension is applied. The magic of a commercial bandsaw blade tension gauge is the dial of the indicator is calibrated in PSI instead of thousandths of an inch or such. So to answer your question, there is no effective difference between the various gauges other than the price and the name.

    The Starrett:

    tension_gauge_Starrett.jpg

    You can make a functional gauge yourself with a standard dial indicator. Make a frame with clamps from aluminum, plastic, or wood. It will work just as well. You can make marks on the gauge dial for the tensions you want or just use the simple math to convert. Some pictures below show gauges made differently but the function is the same.

    Another thing - if you know someone with a gauge they may be willing to bring it over and set the tension for a specific blade so you can repeat it later. (I've done this for several local people - I'm afraid the drive to your house might be a bit much. ) If there is no useful parts remaining on the new saw for this you might devise a pointer or at minimum, experience how much deflection is needed for a specific side force to approximate the desired tension. Or listen for the frequency of the "twang"!

    If you belong to a club that is not mostly broke, they may be willing to purchase a gauge that members could use. I recently did a bandsaw demo at a large woodworking club and afterwards they told me they planned to purchase a gauge for the club.

    You can also rig up a dial caliper with a couple of clamps and measure the blade stretch that way to calculate the tension. One message here described this method and had a photo. I think I even saw photos of a shop-built gauge built like the commercial versions.
    I have saved many messages and files related to measuring tension, some pointing to messages with photos and some with the math needed. I can dig those up if needed but I probably can't get to it for a few days.

    Some other photos from the forum:

    tension_gauge_mreza_salva.jpg tension_gauge_Schierer_Woodgears.jpg


    BTW, I tried calling Louis Iturra just now and for the first time in my many calls over the years he didn't pick up. Of course, it's Saturday so I'll try again next week. With the current health uncertainty, I sincerely hope he isn't ill.

    JKJ



    Quote Originally Posted by roger wiegand View Post
    I've plowed my way through more than I ever wanted to know on the topic.. (eg https://sawmillcreek.org/showthread....mparison/page7) as well as later threads.

    On my little bandsaw I can twang on the blade and guess that the tension will be about right for what I want to do. My problem comes with my new-to-me Centauro-made MM20 with the broken tension gauge. It looks like replacing the factory gauge involves some fairly major disassembly of a saw that is otherwise working perfectly. -- and then, per the myriad earlier discussions of built in spring gauges, may not be particularly accurate or reproducible.

    I thought that a third party gauge might make it easy to set the blade with some reproducibility. I don't care that much about "real" accuracy, I'd just like to be able to consistently get the same tension in the correct ballpark. With the enormous resaw blade in the saw now my "by feel" methodology is failing me-- I can push it or twang it, adjust the tension by two full turns and feel no difference-- it's just stiff, no matter what.

    So, per the earlier thread from a 15 years ago-- Carter, Iturra Lenox Starrett -- it looks like the Carter is no longer sold, can't find it on their web site. I tried to contact Iturra a couple months ago for a different part and had no response to email or phone calls, so are they out of business? EZTension won't work on blades this large. That leaves Lenox and Starrett. Does it matter between them? A Starrett seems to cost a couple hundred more, it that just inflation due to the name?

    Is there a better way that doesn't involve spending hundreds of dollars? I'm not interested in building a DIY device, I just want a quick check to tell me that my tension is in the right ball park-- that I'm not cranking it down so hard I'm in danger of breaking something.

    Or is it worthwhile to tear the saw apart and replace the OEM gauge (assuming the part is available) instead?

  4. #4
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    Maybe it's my farm boy lessons, but I've never fussed over blade tension. I tighten until it's tight, and saw. I've never leased the blade tension over 45 years. Blade sharpness, finger tip control on curves, and feed speeds are the real critical factors in my opinion. I did a room screen 25 years ago and I wanted to resaw a panel taller than would fit under the top guides. I put on a new blade, took off the top guides including the thrust bearing, and got 3 panels out of a 7/8" piece of stock. That verified to me that super guides and tension gauges are overrated. I also have watched Woodmizer bandsaw mills cut 24" logs with just two rollers and a shoulder on back of the rollers. The blade is not guided on both sides with bearings either.
    Last edited by Richard Coers; 10-16-2021 at 3:13 PM.

  5. #5
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    I have used this app from Inkleind with success (his twin turbo vice is very cool as well).
    https://www.in-kleind.com/inkleind-bandsaw-tensioning

    I got lucky and received the Starret gauge with my MM24 I bought used from a fellow SMC member. I have used it on my 1” blade and it seems very repeatable as well as giving me good sawing results. I wouldn’t have purchased it due to its cost but it is nice to have for the reassurance.

    I haven’t compared it to the app yet. I’ll go do that and let you know how the app compares to the gauge.

  6. #6
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    Well you said you don't want to build anything, but if you change your mind here's the gauge I made. I use it to check the tension on my BS and my sawmill. It works as well as a commercial meter for the price of a dial gage and an hour of your time.

    https://sites.google.com/d/1deYVS01k...i=1&authuser=1

    John

  7. #7
    Just so you know, the tension gauge is adjustable on a lot of the Italian saws.
    If the Bowden cable is snapped, you could replace it, but I'd guess it only came loose.
    I happened to loose the little clamp which was on the end of the cable, inside the plastic reader box.
    Haven't found it yet, but made do with making a clamp from a plug, seems good.

    If it is snapped then it wouldn't be hard to replace, but you'd need to take a good few measurements beforehand,
    wheel protrusion from cabinet with beam and shims, and take the pair of pins out of the shaft.
    I will say, beware, beware, beware of those split pins on the screw, if you damage them they might never come out again.
    I'm sure there is a wee tool for the job, I tried making some to no avail, and had to cut my hand wheel off to service my machine, as someone damaged it beforehand, and everything was assembled backwards.

    I'm under the impression that it should look something like this,
    but awaiting on confirmation as I did attempt some happy Centaurolizing with the welder,
    Seems from someone who helpfully replied on youtube, with a newer design ACM made Laguna, that I went too far,
    so is causing some rubbing on the carriage underside at the moment, I can see witness marks from the pin
    so likely I need to grind some off again, or weld and drill a hole a bit lower down, possibly.
    It might be helpful, should it annoy you not to have the gauge, hope I'm not derailing the thread, and you want an actual system of measurement
    rather than something ball park.
    All the best
    Tom

    SAM_4429.jpgSAM_4504.jpg
    Last edited by Tom Trees; 10-17-2021 at 5:11 PM.

  8. #8
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    Seems like a belt tension gauge could be adapted.
    Bill D

  9. #9
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    Quote Originally Posted by John TenEyck View Post
    Well you said you don't want to build anything, but if you change your mind here's the gauge I made. I use it to check the tension on my BS and my sawmill. It works as well as a commercial meter for the price of a dial gage and an hour of your time.

    John
    I was mis-thinking how these gauges work. Looking at your design, there is no tension applied to the frame. I was thinking there was and not understanding how wood with bolted joints could not move as much or more than the few thousandths of an inch that you're trying to measure. But the top and bottom pieces, if I understand correctly now, are not even connected. Thanks for the link and photos, that really looks quite doable!

    Now if I can just figure out how to print the document from Google!

  10. #10
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    Quote Originally Posted by roger wiegand View Post
    I was mis-thinking how these gauges work. Looking at your design, there is no tension applied to the frame. I was thinking there was and not understanding how wood with bolted joints could not move as much or more than the few thousandths of an inch that you're trying to measure. But the top and bottom pieces, if I understand correctly now, are not even connected. Thanks for the link and photos, that really looks quite doable!

    Now if I can just figure out how to print the document from Google!
    That's correct. You are directly measuring the tension in the band. Also correct, the top and bottom pieces of wood are not connected. The dowel pin only loosely fits in the hole in the upper piece, just to maintain alignment. It's a simple build. Better still, it's simple to use.

    As John J. pointed out, I only use the tension meter to find out what setting my onboard pointer registers for each size band I use. Knowing those values, I use the onboard gage when changing blades. So while you wouldn't have to repair your onboard gage you will find it easier to use once you know where it should be pointing for any particular blade.

    John

  11. #11
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    Quote Originally Posted by John TenEyck View Post
    As John J. pointed out, I only use the tension meter to find out what setting my onboard pointer registers for each size band I use. Knowing those values, I use the onboard gage when changing blades.
    John
    OMG!! That's so much better an approach then I've been using. I take out the Lenox gauge with each blade change, and get the blade to the optimum tension (I usually go for 25K).

    Nice tip, John...
    - When God closes a door, he opens a window. Our heating bill is outrageous & six raccoons got in last night. Please God, this has to stop!
    - Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read.

  12. #12
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    I did compare my Starret tension gauge with the Inkleind app and I was very impressed with the accuracy (relative to my uncalibrated but expensive gauge :-) ) and repeatability of the app for my setup!

    I made sure to pretension the gauge and the values on it were repeatable compared to my bandsaw gauge. As expected my bandsaw gauge isn’t close to what it should be reading but at least is somewhat repeatable. I could make a new scale for it but I doubt I ever do more than a pencil mark on it.

    105EA58A-3CAD-4670-AC37-0F0E0F3CF192.jpg 8EF17076-282D-45C0-BC13-89FEA5B2DB64.jpg
    E33C8A56-B476-449F-B84C-F9408F420C4B.jpg FBEE9A67-74B3-4927-8B20-C0674142AAF8.jpg
    2C6329B0-5FA7-438B-80B1-A72FB7A832D9.jpg A987216A-6113-407C-BCDF-30ABB5E04B5D.jpg
    79C04F49-C38B-4070-B55B-96BD7FA00D83.jpg 18893FD9-31B6-4051-83F5-FA5EED818C72.jpg

    Note: The best I can determine the tension should be between 15-20 ksi. My bandsaw is a MM24 (Centauro S 600P) with a 1” carbide tipped Lenox Woodmaster CT blade. I measured 60” between wheels for the input to the app.
    Last edited by Eric Arnsdorff; 10-17-2021 at 11:37 AM. Reason: Added additional note

  13. #13
    I was going to edit my post, but can't, so to address my concern I might add, it turns out that pin moves further away
    from the carriage when the blade gets tensioned,
    and the rubbing marks was coming from dropping the wheel down extremely low.
    Guessing the noise is from the thrust bearing and not the pin!
    SAM_4948.jpg

  14. #14
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    I set my bandsaw tension using the flutter method and it works for me.
    I let the blade flutter and then tighten it until the flutter stops and then I tighten it 1 revolution of the tension crank.
    It works for me.

  15. #15
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    About the simplest bandsaw blade tensioning gauge I've seen is to use a digital caliper. Open the jaws about 5" and clamp each end to an untensioned blade. Zero the readout and begin to tension the blade. Every .001" of blade of blade 'stretch' = so many PSI of tension. The magic is knowing the formula - which I don't. I had it some place but no idea where it got to.

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