Bandsaw blade flutter

[bertterbo]

I often find that when I take my blades out of storage to use (swapping to a different TPI for example) that there is a very noticable "flutter" where (when looking from the front of the bandsaw) the blade teeth go from being oriented to the left to oriented to the right as you spin the wheels. This is nothing to do with the bandsaw setup, but with the blade itself. It seems that it gets bent/twisted when being stored?

Not sure what I am doing wrong, I just fold it as per one of the many techniques you find online and then hang it up.

The blades are Tuffsaws/Axminster.

Will the blade correct itself if I leave it running for a while?
Does anyone else get this?

 

[Spectric]

Are they tensioned enough, swapping from say a 3/8 to a 3/4 would require more tension. When you say fold it up, it should almost fold itself with just a little effort and unfold very easily!

 

[bertterbo]

Are they tensioned enough, swapping from say a 3/8 to a 3/4 would require more tension. When you say fold it up, it should almost fold itself with just a little effort and unfold very easily!

I do it this way, then add a bit of masking tape to keep them from uncoiling. Definately enough tension.

 

[Spectric]

Thats how I do mine so this cannot be your problem as I don't get those issues. Once fitted, tensioned and run does it still show that flutter issue? The big question is how does it cut, if it cuts ok then you cannot have a problem. One other point, are the side guides behind the teeth and not impacting the teeth offset?

 

[bertterbo]

It's not the bandsaw setup as it works fine when the blade is new. It's only after I have stored it for a while and then use again I notice that the blade is twisted.

And yes, the flutter is very noticeable even after the blade is tensioned. As it's constantly switching from pointing left/right as the blade goes around, it results in the bearings spinning, and a wider kerf than normal. It's certainly not ideal!

 

[Spectric]

A new blade gives no issues, so have you tried putting a new blade on and then check there are no issues before then just removing it and refiting again to check all is ok. Then remove blade and fold up a couple of times before again refiting to see what happens. Looking to see if issue is with the folding for whatever reason or something else.

 

[deema]

Tension, blade tension is insufficient. You need a blade tension meter either bought or had home made. Nothing wrong with the blade, it’s just stretched a little.

 

[Spectric]

I think there is a method of blade tension on some video that shows how a blade flutters until you give it enough tension at which point it stops fluttering. Having a proper means of actually measuring the tension has to be the best way to go but @deema what meter do you use or recommend?

 

[Ttrees]

I thought I might have had the same issues before, and chased my tail for a long time and had a long slog with a misaligned machine, doing various adjustments,
whilst also learning a good tire dressing method and whatnot.
It turned out that my wheel bearing spacer on the upper wheel was worn.
I'd have a look at the upper wheel or carriage assembly if running thin gauge blades which seem temperamental at times.

The upper wheel shouldn't have any slop left to right, and would be the first thing I would think about if the blade was fluttering after doing a proper check with table off and a beam

Or rig up your own if you think this is easier with the table on...

Possibly a laser could be used instead?

All methods one could try after the obvious like tire wear or resin build up.

Could be an idea to get a good pen like a Parker refill, (rubber will pull the tip of a Bic off)
and mark about 50 lines around the tires like a coral snake, to see if there are any dips in the rubber.

Tom

 

[deema]

@Spectric I’ve used a Lenox kindly lent to be by Ian at Tufsaws, however in the thread started by Sideways we give the technical details to just use a vernier clamped to the blade.

 

[Spectric]

Hi @deema , I will look up that thread, and also the Lenox because it would be better to become more accurate with blade tension. With rubber belts we used to have what was an electronic tunning fork, it measured belt resonance but I doubt it would work on a blade.

 

[--Tom--]

Hi @deema , I will look up that thread, and also the Lenox because it would be better to become more accurate with blade tension. With rubber belts we used to have what was an electronic tunning fork, it measured belt resonance but I doubt it would work on a blade.

People have come up with ways using a guitar tuner to measure the pitch and have a degree of repeatability

I managed to get a Starrett gauge from eBay for a good price, works really well and takes a lot of the faff out of setting the tension

 

[bertterbo]

Pretty sure it's not tension. I have wound the tensioner until it's almost too stiff to turn. Far more tension than I normally would feel is appropriate.

 

[deema]

I suspect your tension spring has been over compressed and is no longer providing the correct tension. It probably needs changing. Unfortunately springs have a max they can be compressed and bandsaws don’t have bump stops to prevent over tensioning. You are therefore not generating the tension required for the blade. See the SCM restoration thread started by Sideways. I go through a detailed explanation of the spring constant, how to verify and calculate what it should be and what it is.

 

[bertterbo]

Why would it be OK with new blades then? Even new blades that are wider and would require more tension?

 

[deema]

@bertterbo may I suggest you read the thread I’ve suggested, using the data and method evaluate your machine and if there are still any queries shout out. Otherwise it’s pure guess work, the symptoms would suggest blade tension / tension spring issues.
It could have been a dud blade, but you suggest you’ve had this issue with more than one Tuffsaws blade. That rules out a blade issue, Tuffsaws are excellent blades. The blade isn’t coming off the wheels so it’s not wheel alignment. It has nothing to do with blade guides, I’ve written a thread about what blade guides and what they don’t do which you can look up if interested. You don’t say that there are any issues with the tyres so that only leaves blade tension which is the most common issue.
A fluttering blade is a blade which hasn’t enough tension applied to it.

 

[Spectric]

You mention what blades you are using but not what machine unless I have overlooked that info, it may help to know make and model because it gives an idea as to the machines capability and if there are known issues. Bandsaws can be really finicky and need that extra attention to detail to keep them running at their best and there are a lot of variables but with your symptoms it does point to tension. My BS400 states it can use a 1 inch blade but I find the machine cannot tension this size of blade and as a result it delivers very poor cuts.

 

[Fergie 307]

Why would it be OK with new blades then? Even new blades that are wider and would require more tension?

I had some similar issues. Now store spare blades hung over a semi circular piece of ply on the wall, so not as it were folded up, but just as they would be on the machine. Never had a problem since.

 

[Spectric]

These blades are like spring steel and so unless you force them into tighter bends than they are happy with they should not deform but may stretch over time.

On my BS400 I always leave the blade untensioned, less strain on the machine frame and blade.

 

[Ttrees]

@bertterbo
A fluttering blade is a blade which hasn’t enough tension applied to it.

I think an under tensioned fluttering blade is likely a tell tale sign that something isn't right.
Was very pleased to eliminate the side to side fluttering after dressing with a half tensioned blade, not that hand turning the wheels with a half tensioned blade is a good idea with flat tires.
The fluttering was still apparent before at near tension, as there's small window of allowance on flat tires since tension affects tracking in a big way on mine,
and was less apparent at full tension.

I look forward to getting my saw back together and might try some hand tracking on some old blades
to see how they react now, I wont be using them as is,
as to my mind some of them seemed warped to me.
Not helped by the set being compressed, which is a knock on effect regarding damage fighting with the blade to finish the last few inches.

I reckon these blades will still flutter because of damage.
Some more pics I forgot to add
The drive belt must be loose to make above adjustments, and sighted down to see alignment with motor pulley before running!!!

Leveled prior as I have carriage and shaft adjustment for upper wheel on my machine

This is how to use these plumbobs, blocks and lighting!

Tom