Bandsaw Blade Tensioning - again

[Ken Casser]

I know this has been gone over and over, but for some reason, with all I've read, I'm still not comfortable, so please share your experiences.

I have a 1992 Delta 28-203 with riser block. I've done all the tuneups, drift correction, etc, etc. It cuts very well, but I just want to be sure I'm tensioning my blade correctly - not too tight, not too loose.

I'm using a Timberwolf 1/2" - 105 - 6 tpi. Here's my quandry: I tension it according to Timberwolf's instructions, and don't seem confident in finding the point where the flutter stops. It seems to stop fluttering at different points each time I do it. So, I tried "plunking" it like a guitar string to find that "bass clef low 'F' note" per Russ Fairfield, and I can only get it to about a muddy "C" when the tension scale reads halfway between 1/2" and 3/4". Now I know I've read that proper tension for a 1/2" blade should put the tension scale at 3/4", but I've also read that Timberwolf blades require less tension than others. Sooo, would you say I'm safe in heading towards that 3/4" mark and going for that true "F" note, or is that going to be stressing the Timberwolf unnecessarily? My thinking is that if I reached that "F" note, my flutter would be gone for good. I would consider getting a tension gauge, but can't justify spending the $ for something I would use once or twice (not that I haven't done that before:eek:)

Thank you for your advice. If nothing else, I've been having a great time bringing this saw up to speed.

Ken

[Myk Rian]

I just bought a 105 1/2" 3tpi Timberwolf yesterday. You will notice the flutter the instructions refer to is very pronounced. Like 1/4" flutter. My Delta 28-299 is set near the 3/4" mark. Nice blade. I resawed some 1/32" veneer from a 6" board with it.

What guide blocks are you using. I made some out of walnut and soaked them in WD-40. The blade is buried in the blocks. Works like a dream.

[glenn bradley]

I run Timberwolfs and use the flutter method on my 10" and 17" saw. The flutter is small and seems irregular in position on the smaller saw. The flutter is very distinct on the larger saw. I just attribute the smaller saw's behavior to the ability of the machine to "hold still". With a riser you may have some flex going on as well.

I don't get overly concerned about it. Once I find "the spot" I just back the tension knob off a few turns (pick you number) and re-tighten the same amount when I am going to use the saw. After a bit I will notice some drift and I am sure the tension varies with the nature of the saw as described; I just readjust as it only takes about a minute.

The large saw has no problems even though I de-tension/tension the blade; sometimes several times a day (not intending too, just happens, bad planning) and then not for a week, There is probably still variation there. Maybe just less noticeable or impactive due to scale, blade width, etc.(?). Just guessing here.

[Ken Casser]

Thanks, Myk! Do you always tension it close to the 3/4" mark? or is that tighter than normal because of the 1/32" resaw you were doing? Also, I forgot to mention that I replaced the old spring with a Carter, so that may have a bearing on how far to push the tension scale. Sweet guide blocks! I'm using the stock guides that came with the saw. They seem to work fine, but I might try making my own.

Glenn, yeah, the riser may be causing the flutter to phase in and out, but when there's any flutter, the cut suffers. I want to figure out how far to push it without damaging anything. A friend of mine just bought a brand new 14" saw with quick release (I won't say what brand, but the saw cost him about $1200), and put a 3/4" blade on it. While tensioning it to the recommended mark, a couple of teeth on the quick-release broke off. The company was terrific in sending replacement parts, but he's scared to death to tighten things too far now. I think his issue was a fluke and that he should be able to crank it down completely compressing the spring and hurl railroad ties at it, but of course we would never do that.

[Myk Rian]

I have a 93" - 3/4" blade that I tried to mount on the saw before I got the riser. I couldn't get enough tension on it. 3/4" is pretty wide for a 14" saw anyway. It was very hard getting it to track.
I am using the stock tension spring on the saw. The top of the tension nut is near the 3/4" mark, but that is really just relative. Blades aren't all the same length, and of course the springs can have different stiffness.
I didn't want the metal guides to start heating the blades. The wood ones can be tucked in nice and close to the blade with no fear of that.

[Pete Bradley]

Don't overthink it. There's no need to go nuts on tension, but there's enough leeway in the normal range that it's not rocket science. Whatever gets the flutter out and keeps it out is fine. For tall/difficult cuts you may need a little more. Band saw scales are at best a suggestion and a different spring will change the actual tension at a given mark, so just find what works for you.

I'm dubious of the value of quick release in general, and I wouldn't draw any conclusions from your friend's experience for your saw.

Pete

[david brum]

Hi Ken

I've been using a generic 14" saw with a riser and Iturra spring. For a Lennox 1/2" blade, I used the 1/2" setting on the saw with no problems. The Timberwolf should require slightly less tension, if anything. Those springs are pretty stiff.

I think the main concern with blade tension is making sure your resawn boards don't have a bowed face. In other words, if you put a straight edge on your board, it should be pretty flat. An undertensioned blade can flex enough to screw up the flatness. Whatever tension gets you a flat cut is the right amount.

Keep in mind also that resawing with too many teeth can cause cutting problems that no amount of tensioning can cure. If resawing is your goal, you will probably have a much easier time with a 3tpi blade.

[Ken Casser]

Thanks, Pete. I think it's one of those things where, 'it's easy when you know how.' I had a Craftsman 12" for years and never gave it a thought. But this Delta came with a bent tracking hinge which I replaced with the improved Iturra, and I'm trying to find my feet with the tension without going past the dropping off point. I think I'll play with a narrower blade for a while and see if I can learn from that. BTW, too late, I'm already nuts.:D:D

Good advice, David, about the 'bowed face'. I'll store that thought for the future. I'm not resawing yet, I'm cutting dovetails at the moment, but I understand that thicker wood needs fewer teeth. I also realize that there are too many variables for me to get a definitive answer (spring, brand of blade, markings on the scale, etc.), but I think I'm getting more comfortable.

I'm really curious to know if anyone uses that "bass clef 'F' note" technique. Russ Fairfield claims that it gives you very nearly 12,500 psi, and I would think that this would be quick, easy and accurate.

[Mike Cutler]

I'm really curious to know if anyone uses that "bass clef 'F' note" technique. Russ Fairfield claims that it gives you very nearly 12,500 psi, and I would think that this would be quick, easy and accurate.

You can drive yourself crazy with all of the tension strategies, or just use the installed tension gauge on the saw as a beginning point. They are not as inaccurate as people might think. If you can hear the bass F Russ refers to, there is no reason not to use that as a starting point.
The key point is that the spring has to have gaps between the coils, or you have no spring. No spring equals no bandsaw,and it's a guarantee that you will break something if the spring is fully compressed on a bandsaw.
If you want to use an aftermarket tension gauge, get the one that Carter seels that mounts under the tension screw. It measures in lbs wheel force, but is very easy to convert to psi using Young's modulus. Stay away from the ones that clamp to the blade. They are very finicky to obtain repeatable results. The Carter is very repeatable, just a different readout.
I've never bought the low psi blade stuff. Steel is steel, to a point of course, and within a range of probability it will have the same modulus of elasticity. Just a personal opinion here.

Set the tension gauge on the bandsaw to 1/2", make sure you have a functioning spring, and start resawing. Look for barreling to let you know you need more tension.

[Phil Thien]

My bandsaw doesn't have a scale and I'm pretty confident in my ability to tension it properly. But I would love to hear a bass F note (I don't have a piano). Is there a wav file of what that note sounds like so I might compare it to my saw?

[Ken Casser]

I guess if we're getting good cuts, we know that the tension is tight enough. Too bad we have to waste wood on a poor cut to find out we're too loose. But thank you for the good advice, Mike. I think I have made too much out of this.

Phil, I Googled and Googled to find that sound, but couldn't. What I did do is use an old harmonica I had stuffed in a closet to give me the note. A pitch pipe, used in tuning stringed instruments, would be an inexpensive way to compare sounds. I'll keep looking for a wav file, though.

[Phil Thien]

Phil, I Googled and Googled to find that sound, but couldn't. What I did do is use an old harmonica I had stuffed in a closet to give me the note. A pitch pipe, used in tuning stringed instruments, would be an inexpensive way to compare sounds. I'll keep looking for a wav file, though.

Yeah, I googled before I asked and couldn't find anything.

[Steve Leverich]

Guys, having been a half-a**ed musician since I was 5 (about 58 years ago) I have problems with a generic recommendation for a specific frequency for any and all BS's -

Think of the BS blade as a guitar string - to change the pitch on a guitar string, we place our finger(s) against the string, which holds it against a fret on the guitar, SHORTENING the section that's vibrating, and RAISING the pitch - Initially, the guitar is tuned to specific notes per string with the strings NOT fretted against the neck.

True, tightening the tuning pegs (increasing blade tension) will raise that pitch, BUT - so will changing the LENGTH of the vibrating section by pressing against a fret on the neck.

If you have a RISER on your saw, and the "low F guy" has NOT (or vice versa) then you're tuning your blade to the wrong note.

If you have a different blade (thickness, metallurgy, width) then your "string" will vibrate with a different pitch when it's at the SAME tension as the other guy's blade.

If you "tune" your blade with the guides touching the blade and the other guy RETRACTS his guides, it's a different song. Same with a DIFFERENT 14" saw - not all have the same distance between wheels, so again, different "string" length and different note (pitch)

Besides music, I've also worked in process instrumentation in the rare metals field for the past 30 years, so I know there are several other possible variations in blades to further cloud the issue - bottom line, in my experience - find another way.

I'm liking the "inductive" approach of "make it work", as Mike Cutler posted... Steve

[Mike Cutler]

I guess if we're getting good cuts, we know that the tension is tight enough. Too bad we have to waste wood on a poor cut to find out we're too loose. But thank you for the good advice, Mike. I think I have made too much out of this..

It is a shame to waste wood, especially with the current prices for quality material. It also seems that once you arrive at a nice setup for one species of wood, you have to go through the trial and error to find a setting for a different wood.
I usually work with the really hard tropicals,and they can be hell on blades. The setup seems to require just a little more tension, or slow down the feedrate.
Sometimes it fun to work with "soft" American wood like maple and oak. :eek:,;)

[Chris Padilla]

I dunno...if you're confident of the general setup of your bandsaw (coplanar wheels, blade in the right spot on the flat or crowned wheel) and have the guides dialed in snug but not overly tight, the blade tension shouldn't be such a big deal.

I dunno, maybe I'm lucky with my MM20 but I tuned it all up once long ago, and now I just slap blades on it and crank the tension until I can deflect the blade about a 1/4" and it feels tight, and cut away. I get very satisfactory results.

IMO, I think half of a good cut on a BS is tuned up equipment and the other half is technique cutting. Perhaps the "third half" is the blade and some combination of its tension. Personally, I haven't found any "magic" spot (tension) that makes me cut better than another spot.

Any crappy resawing I get is due to me not properly steering the board or forgetting to make the blade to top perpendicular and the fact that I am more or less a beginner resawer who is learning.

I have to admit that the MM20 is my one and only bandsaw I've ever used so perhaps I don't appreciate what you 14" guys are dealing with.

[Phil Thien]

True, tightening the tuning pegs (increasing blade tension) will raise that pitch, BUT - so will changing the LENGTH of the vibrating section by pressing against a fret on the neck.


I had considered that, but please indulge me while I lay out a kooky theory...

It would seem to me that increasing blade span by moving the wheels further apart, without a corresponding increase in blade tension, may be inviting blade vibration/flutter.

So I have this crazy notion that perhaps the best way to find a starting point to tension a blade is to tension it to a specific frequency. This way you don't overtension a blade (thereby increasing wear and tear on the blade and saw), and don't undertension it, either.

So while I'm happy with my ability to tension my little Delta 10" bandsaw and I'm actually able to slice razor-thin 7" veneers with it, I would like to research the F thing a little.

So I'd still like to hear the note if anyone knows of a way to do this.

[Paul Ryan]

Ken,

I can truely attest to the statement the those guages are just a guesstimation. I have a 4 month old G0555 saw. I have a riser on it. I bought blades for it from suffolk machinery (timberwolf blades). One of the blades they suggested I use was a 3/4 3tpi blade for resawing. I put that blade on about 2 months ago and set the guides up and had it all ready to roll. I kept seeing the blade flutter at different tensions too. So I kindof found what I felt was the best spot. I didn't get a chance to cut that night so I flipped the quick release lever and away I went. A couple of days latter I had a chance to cut the wood I planned on. I went out to the shop got the band saw pushed out and started cutting. Half way through the cut I realized oh crap I forgot to retension the blade. I finished the cut and it was about a 5" resaw. The cut was pefect. I cut the rest with no problems. Beautiful cuts very little clean up on the planner or jointer. When I checked the blade tension guage it was set below the 1/4 blade setting. So very little tension on that 3/4" blade.

The moral of the story is, I do believe that timberwolf blades take much less tension. But those guages don't mean crap. I have since resawed about 60 br ft with it set that way and continues to cut beautifiul. I am by no means a bandsaw expert, but you just have to play with it and see what works best for your saw.

[Ken Casser]

Steve - You've made some very good points that I hadn't considered, even though I was a guitarist from age 8 to 24 (Berklee College of Music for a year, too). I'm embarassed to admit that I hadn't thought about the length of the span as being a factor. I still don't know why I'm stuck on "C" no matter how tight I go, but I think I've beat this one to death. Mike and Paul have it right - play with it and move on.

Phil - to clarify what I said above about "C", with my 1/2" 6 tooth Timberwolf blade, and with the 3/8" as well, I can get a clear "C" note out of it, but even tightening it and tightening it, it still stays on the same "C" note. I can't get it to increase in tone. I don't know why. I'll have to go back to music school. Let me know what you find, though, if you pursue it.

[Steve Leverich]

Phil, here's a way to hear your note if you have fairly healthy speakers on your computer (some sort of 2.1 system, for example)

Download and install this

http://www.satsignal.eu/software/audio.html#SweepGen

Then go here

http://www.phy.mtu.edu/~suits/notefreqs.html

I'm going to assume that the particular F note in question is the lowest string on a bass guitar, fretted up one semi-tone from low E - this would make it F1 on the chart, or 43.65 hZ. So you would set the sweep gen software to wide range (20-20,000) and (hopefully) adjust the slider for the desired frequency - I've not used this particular application, so it may or may NOT be finely adjustable enough.

In answer to your "kooky" idea, maybe - I've found out sometimes the hard way, that too many other factors rear their ugly heads when I make assumptions. For example, flutter may be introduced by wobbly wheels, in which case changing blade length might get the blade resonance further away from the disturbance induced by the wheel wobble - in that case, flutter would improve. Things like motor speed, belt ratios, wheel diameters, etc, would also have an effect.

Without studying the specific case, I'd rather not venture a guess as to what will cause what - I've only put forth a few things to examine in case any of them weren't originally considered; hopefully someone will find use for them in their own search... Steve

[Bob Slater]

My bandsaw doesn't have a scale and I'm pretty confident in my ability to tension it properly. But I would love to hear a bass F note (I don't have a piano). Is there a wav file of what that note sounds like so I might compare it to my saw?

You can find an online guitar tuner with the following notes EADGBE . No F though
http://www.guitarforbeginners.com/onlinetuner.html

[Phil Thien]

Okay, I found an online Piano here:

http://www.play-piano.org/play_online_piano_piano.html

But I'm not sure if the suggested F is F1 or F2 on this piano. Anyone more musically inclined that can enlighten me?

[Steve Leverich]

That is only a 5 octave keyboard, the F you want is off the lower end. The bottom note on this one is approx. 64 hZ, so it would need one more octave to include the next "F" downscale... Steve

[guy knight]

buy a tension gauge and then adjust the gauge on your bandsaw so you always know what the correct tension is

[Rick Fisher]

http://www.primaryresources.co.uk/music/piano.html

:)

I am with Chris. I tighten it up until its nice and snug and just start cutting.
My saw has a metric scale on it which says 15,20,25,30 etc...

No idea what it means but I just set it between 25 - 30 and cut.