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Thread: Bandsaw Blade Not Running Smoothly

  1. #1
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    Bandsaw Blade Not Running Smoothly

    Saw - Laguna 14 twelve
    Blades - 3/16" 4 TPI
    Issue - I have had several blades that, as I cut with them, seem to cut, then bog down, then cut, then bog down (hitching might be a good description). This is as soon as I install them for the first time. If I take the blade off and put another on, it cuts smooth and cleanly. Most of my work is bandsaw boxes, so thickness of the wood tends to be around 4". I am using a Carter Blade Stabilizer, so contact with the guides by the blade is not an issue. Welds seem to be good.

    Thoughts?
    Mike

  2. #2
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    I have certainly experienced this (although I am using wider blades). I can think of two theories: First is variations in wood density, but that wouldn't explain why changing the blade makes a difference (unless you are changing wood blank too). Second is too fast feed rate for the blade in use, causing sawdust to pack in the cut. Once the increased feed pressure causes you to slow down, the cut clears and things speed up again. Just a theory. That small blade can't clear sawdust very fast so maybe that's the issue.
    --Certainty is the refuge of a small mind--

  3. #3
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    Check your drive belt tension, it could be the belt is slipping when you hit harder sections of the wood.
    Lee Schierer
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  4. #4
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    Thanks for the input. I don't believe these are the case.

    1. "First is variations in wood density" You are correct. Same block of wood.
    2. "Second is too fast feed rate for the blade in use" Again, the same conditions for the different blades.
    3. "Check your drive belt tension" As per comments above. I believe it is something to do with the blade itself. Poor set to the teeth, some sort of inconsistency etc. Provider of course refused to accept even the possibility it had anything to do with the blade.

    Thank you for your time.
    Mike

  5. #5
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    Let's say your bandsaw blade speed is 3000 feet per minute (ballpark for wood cutting bandsaws). Lets say the blade is 10 feet long. That means the entire length of your band passes the table 300 times per minute, or 5 times a second. If there was an issue with blade set or the like, it would feel more like a flutter and would likely show up in the cut quality. From your description, the variation in cut speed sounds slower than 1/5 of a second.

    Is your stock rough sawn? Is your table waxed? Could the stock be hanging up on the table or fence?

    Do you see slivers of wood stuck anywhere behind the blade? Sometimes feathers from the cut get hung up on the far side of the blade insert.
    --Certainty is the refuge of a small mind--

  6. #6
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    I’m no math wiz, but I’m pretty sure the entire band is not rotating through the table completely; five times every second.

    Does it really , and I’m just ignorant ?

  7. #7
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    Quote Originally Posted by Dave Sabo View Post
    I’m no math wiz, but I’m pretty sure the entire band is not rotating through the table completely; five times every second.

    Does it really , and I’m just ignorant ?
    Seems fast to me too, but I stand by my math Later today I'll measure mine...
    --Certainty is the refuge of a small mind--

  8. #8
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    Dave - This is approximately correct. I had never thought about it in these terms but it is moving quickly.

    Compared to a table saw though this isn't that fast.

    My table saw runs at about 4000 RPM = 66.7 revolutions per second blade speed (10" diameter => 31.4" or 2.61' circumference). This means the fpm equivalent would be 2.61'*4000RPM = 10,466 fpm. This is very slow in comparison to my table saw.

    In either case, the discussion is valid that an area of a blade having a bad spot would occur at a much higher frequency than what is being described.

  9. #9
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    Quote Originally Posted by Dave Sabo View Post
    I’m no math wiz, but I’m pretty sure the entire band is not rotating through the table completely; five times every second.

    Does it really , and I’m just ignorant ?
    It does. Actually for the typical 14" Delta clone running a 93.5" blade at 3,000 fpm it is 6.4 times per second.

  10. #10
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    If the problem does NOT involve the band slipping, belts slipping or motor issues (motor issues should be audible) then we focus on the band geometry. If the kerf and teeth get loaded with spoil and blast themselves free every so often, that can cause an irregular pulsing to the feed rate. Not to go all weird-science here but we are starting to split hairs. I experience this on a variety of woods with a variety of feed rates. Adjusting the feed rate to the material by listening to the sound of the machine and cut generally solves this for me. This of course, only works if the problem is blade/spoil related.

    If there was a bad tooth pattern or set the occurrence would be very frequent and consistently repeating. I don't know that I would chase that too far since I believe you are reporting a more random and less frequent occurrence(?). If the band or belt are slipping (not stopping) the slowing and hastening of the band speed could also cause this. I would expect there to be some audible indicator if this were occurring. You could try making test cuts with your DC off in case that is hiding an audible clue. Please let us know what you find out.
    Last edited by glenn bradley; 03-03-2021 at 10:04 AM.
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  11. #11
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    I measured my 18 BX using a phototachometer with a single reflective dot attached to the blade. It measured 317.1 revs per minute or 5.3 per second. The 18BX has a 145" band, so that corresponds to a blade speed of 3832 feet per minute.
    --Certainty is the refuge of a small mind--

  12. #12
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    One other thought. I've noticed on some wood that there is tear out on the bottom of the cut that sometimes hangs down and catches on the throat plate, causing you to push slightly harder which then breaks the fibers and you cut quickly again. This is a random occurrence and has nothing to do with wood density. Higher moisture level wood or stringy grain tend to do it more than really dry wood.
    Lee Schierer
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    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  13. #13
    "I have had several blades that, as I cut with them, seem to cut, then bog down, then cut, then bog down (hitching might be a good description). This is as soon as I install them for the first time. If I take the blade off and put another on, it cuts smooth and cleanly."

    I am unclear. Are you saying that this problem happens with multiple blades but only when you use them the first time? Do they eventually settle out to smooth cuts when you reinstall them?

    Are the ones used when you "put on another" from the same set? Or older blades?

    Could it be that the 'good' and 'bad' blade you are using are slightly different lengths? might you be undertensioning one? How are you certain that the conditions are the same (not doubting that you are certain; just doubting my interpretation of your description).


  14. #14
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    Quote Originally Posted by Prashun Patel View Post
    I am unclear. Are you saying that this problem happens with multiple blades but only when you use them the first time? Do they eventually settle out to smooth cuts when you reinstall them?
    No and no. It happens right away and does not change with use.

    Quote Originally Posted by Prashun Patel View Post
    Are the ones used when you "put on another" from the same set? Or older blades?
    Usually the "faulty" blade is from the same order as the ones that work correctly.


    Quote Originally Posted by Prashun Patel View Post
    Could it be that the 'good' and 'bad' blade you are using are slightly different lengths? might you be undertensioning one? How are you certain that the conditions are the same (not doubting that you are certain; just doubting my interpretation of your description).
    Length could be slightly different, indeed, I have often noticed that I have had to change the tension setting significantly to achieve the same tension. I set tension every time I put on a blade, so that factor should not be relevant.

    I am afraid that none of the other suggestions in the other posts are relevant either. I am not aware of any changes in conditions when blades, which leads me to believe that the issue has to do with the blades themselves, and poor quality control. I was really trying to determine if there was experience out there that would lead me to an answer that I had not thought of. Unfortunately, the blade producer had little to offer other than suggesting that I must have done something to the blades to damage them, like having them so poorly tracked that they rubbed on a metal part on the saw and damaged the set. (This may be a reasonable explanation if it occurred once, not several times). Their response quite clearly refused to entertain any possibility that they could be at fault. The comments here have only reinforced my belief that it is a manufacturing issue.

    Thank you all for your time. Much appreciated.
    Mike

  15. #15
    How about cleaning the bands and wheels? Could it be that they were contaminated with something causing them to slip?

    I really doubt you ruined the set. Itís hard to do that on a bandsaw blade. I know this because i have dropped, stepped on, scratched blades when storing them or coiling them. And to do it on multiple? Just doesnít feel logical.

    I wonder if they were just incorrectly sharpened.

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