Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 41

Thread: Bandsaw tensioning redux

  1. #16
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    7,752
    Quote Originally Posted by Curt Harms View Post
    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.
    Young's Modulus x blade stretch / caliper opening = psi

    30,000,000 x 0.001/5 = 6000 psi

    John

  2. #17
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    6,087
    I just pluck the back of the blade until it sounds about right.

  3. #18
    Quote Originally Posted by Tom M King View Post
    I just pluck the back of the blade until it sounds about right.
    That is just for rough tuning. For fine adjustment, you need to push your finger on the side of the blade to check deflection

    It's low tech, but it works. I don't think I have ever seen a bandsaw blade tension gauge in person.

  4. #19
    Join Date
    Sep 2013
    Location
    Wayland, MA
    Posts
    2,827
    Quote Originally Posted by Andrew Seemann View Post
    That is just for rough tuning. For fine adjustment, you need to push your finger on the side of the blade to check deflection

    It's low tech, but it works. I don't think I have ever seen a bandsaw blade tension gauge in person.
    As noted, those two techniques are the one's I've used for decades. I just have no frame of reference for the big, heavy resaw blades on the new saw to know how much it should bend or the note of the twang. Thanks to a kind Creeker I'll shortly have a gauge that will provide that reference point.

  5. #20
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    6,087
    I do the same for anything from the 1/8" blade on one of the 10" saws, to the 1" blade on the 24" saw. The first cut, if you want to make a test cut, will show if it's okay. Never had a problem with bad cuts, or broken blades.

  6. #21
    Join Date
    Feb 2003
    Location
    Doylestown, PA
    Posts
    6,724
    Quote Originally Posted by John TenEyck View Post
    Young's Modulus x blade stretch / caliper opening = psi

    30,000,000 x 0.001/5 = 6000 psi

    John
    Thanks John.

  7. #22
    Join Date
    Feb 2017
    Location
    Northern Illinois
    Posts
    728
    I don't use a tension gauge. It seems like a waste, especially if the gauge is pricey. For about 10 years I've followed Alex Snodgrass's (Carter) setup process and I get consistent great results. His recommendation is to check the tension on the blade inside the cabinet on the rear where you can rest your finger on the frame and push consistently. If the blade is tensioned so that you can deflect the blade about 1/4" without turning your finger white, he says that always works for him. I sometimes add a little bit more tension, but generally that's what I follow. It works for him. More importantly it works for me.

  8. #23
    Tom,

    A440 ?

    more words
    more words
    what to Mimes do when on a forum

  9. #24
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    6,087
    Not sure if I'm the Tom that question was intended for. I should have put my two posts together. I get paid to produce work. Haven't had much time, or at least, don't take much time to worry about theory.

    Here are my two posts in this thread, that should have been together:

    I just pluck the back of the blade until it sounds about right.

    I do the same for anything from the 1/8" blade on one of the 10" saws, to the 1" blade on the 24" saw. The first cut, if you want to make a test cut, will show if it's okay. Never had a problem with bad cuts, or broken blades.

  10. #25
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    7,752
    Quote Originally Posted by Tom M King View Post
    Not sure if I'm the Tom that question was intended for. I should have put my two posts together. I get paid to produce work. Haven't had much time, or at least, don't take much time to worry about theory.

    Here are my two posts in this thread, that should have been together:

    I just pluck the back of the blade until it sounds about right.

    I do the same for anything from the 1/8" blade on one of the 10" saws, to the 1" blade on the 24" saw. The first cut, if you want to make a test cut, will show if it's okay. Never had a problem with bad cuts, or broken blades.

    An inexpensive, simple to make, and accurate tension gauge is a great help to those of us less gifted. I can report that on my Grizzly G0636X it's really easy to over tension a 1" carbide blade. I went from 24 ksi to 42 ksi in about 1/2 turn of the tension wheel. 24 ksi is a great operating range for a carbide blade where you get good performance and long life. 42 ksi will give even better performance but likely substantially lower life. At $165 for that blade I want to know what the tension is.

    John

  11. #26
    Since some have mentioned it already..
    I'd love to hear what a 1" 24 ksi blade sounds like when plucked, and if that tone is much different to say a 3/4" blade of the same type,
    or even if those welded tips change/deaden the note compared to regular blades.
    Any talk on this is very interesting, and I'm very appreciative of John's wee remarks now and again.
    Going to be a bit more careful from now on, thank you.

    Any other tips or other remarks on how much white finger you get from doing the half or quarter inch deflection test would also be
    graciously appreciated.
    I reckon probably half of the folks using a large machine are waiting for someone very fimiliar with these ksi figures to post a video on this subject,
    as they have a wee bit to go yet before they use their bandsaw to close to its capacity.
    Small bit of a rabbit hole to go down for me to spend a week getting to grips with everything, even after watching a few videos on the subject,
    I'm not really anything the wiser after watching some ForrestMFG videos either.

    Hope this thread keep going
    Thanks
    Tom

  12. #27
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    6,087
    I would have to do each to think about what it sounds like. I couldn't begin to tell you. It's not something I think about. Probably as much feel as sound.

  13. #28
    Join Date
    Apr 2005
    Location
    Central MA
    Posts
    1,426
    Quote Originally Posted by John TenEyck View Post
    An inexpensive, simple to make, and accurate tension gauge is a great help to those of us less gifted. I can report that on my Grizzly G0636X it's really easy to over tension a 1" carbide blade. I went from 24 ksi to 42 ksi in about 1/2 turn of the tension wheel. 24 ksi is a great operating range for a carbide blade where you get good performance and long life. 42 ksi will give even better performance but likely substantially lower life. At $165 for that blade I want to know what the tension is.

    John
    Careful, theres a good chance youre right at the limit of the spring and stacking it if you went from 24k to 42k in a half turn. This is the perfect example of why measuring tension accurately is so important as we approach the limits of our machines.

  14. #29
    Join Date
    Apr 2020
    Location
    Tennessee
    Posts
    341
    Blog Entries
    1
    I'm not sure about the 42 ksi. I'm not a metallurgist and I haven't studied the properties/materials of bandsaw blades. I do understand that properly heat treated carbon steels (with alloys) can provide well over 100 ksi yield strength. I typically use 30 ksi for a quick strength analysis for construction carbon steels to get me in the ballpark. This is also why I'm tentative to go much beyond the 20 ksi that I've seen as an upper end for bandsaw blade tension. I don't have any calibrated methods to measure this and before having an uncalibrated gauge I've tried to use some of the flutter methods and such because going from a flutter to no flutter seems to be the safe side of blade tensioning.

    My understanding of how bandsaw blades are joined is it is typically a resistance weld at the seem that is simply ground flat.

    Will bandsaw blades really take the 40 ksi (or more due to uncertainties)?

  15. #30
    Join Date
    Apr 2020
    Location
    Tennessee
    Posts
    341
    Blog Entries
    1
    Quote Originally Posted by Tom Trees View Post
    Since some have mentioned it already..
    I'd love to hear what a 1" 24 ksi blade sounds like when plucked, and if that tone is much different to say a 3/4" blade of the same type,
    or even if those welded tips change/deaden the note compared to regular blades.
    Any talk on this is very interesting, and I'm very appreciative of John's wee remarks now and again.
    Going to be a bit more careful from now on, thank you.

    Any other tips or other remarks on how much white finger you get from doing the half or quarter inch deflection test would also be
    graciously appreciated.
    I reckon probably half of the folks using a large machine are waiting for someone very fimiliar with these ksi figures to post a video on this subject,
    as they have a wee bit to go yet before they use their bandsaw to close to its capacity.
    Small bit of a rabbit hole to go down for me to spend a week getting to grips with everything, even after watching a few videos on the subject,
    I'm not really anything the wiser after watching some ForrestMFG videos either.

    Hope this thread keep going
    Thanks
    Tom

    Tom I don't have anything definitive on the tones for carbide tipped blades either. The Inkleind app uses the tone method and does have an entry for if the blade is carbide tipped or not. So I assume that Andy Klein found that it did have some impact. Maybe look through what he posted to see if he offers any tidbits on this. Or send him a note to see if he'll share more of his data.

    As far as the tone for different width blades goes - quite clearly this does have an impact on the tone. Both science and musical instruments support this and there is a lot of science around this aspect. The unsupported distance, thickness and width are all factors in the resonate frequencies.

    Maybe you're asking if we could hear the difference. This is a very different question. My musician friends can hear things I cannot to a level that amazes me. I'm not gifted musically in any fashion. I can barely tell the difference between a $5 radio and a $50,000 sound system (other than one usually is louder than the other). So I'd say that some people could definitely use this method by ear and achieve very good results. I cannot so I use other tools.

    One further item is the 24 ksi value you mentioned. As I indicated in my previous post - I have seen the range of 15-20 ksi as recommended. There's not great info on this other than experimentally seeing how good my cut is and using a consistent method to tighten the blade. There seems to be a lot of variations between gauge measurement methods (although stretch/strain as measured with my Starrett gauge would seem to be a reasonably accurate measurement method for tension/stress). I've even contacted Lenox who said to ask my bandsaw manufacturer. My bandsaw manufacturer states in the manual to ask the blade manufacturer. Neither on of them are very useful. So until something better comes along I'll just go with how my blade seems to be cutting and trying to be consistent with how I tension the blade.
    Last edited by Eric Arnsdorff; 10-20-2021 at 11:38 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •