Bandsaw making scary noises

[Mike OMelia]

I was resawing some blood wood about 3.5" tall on my 3hp Jet Bandsaw, 1.125" Resaw King blade. The saw would make a loud thud noise that I could feel, and it would effect the cut (suddenly move a little faster). But it sounded very bad. So I adjusted the thrust bearings to a solid contact, and it seemed to minimize it. Then, when cutting a 6" tall piece, it made the sound louder. Appears that the table jumped too. I inspected the blade, weld looks good, no missing teeth. 3 tpi. Anyone know what is happening?

[Irish Tomás Mac Giolla Ghunna]

Hey Mike would you describe it like on that ...
having problems resawing cocobolo with rikon bandsaw and woodmaster ct blade ..
at 60 seconds into the vid ?

[Mike Chalmers]

Hey Mike would you describe it like on that ...
having problems resawing cocobolo with rikon bandsaw and woodmaster ct blade ..
at 60 seconds into the vid ?

What does this mean?

[Bruce Page]

What does this mean?

I'm assuming he meant to link to this video.


https://www.youtube.com/watch?v=YqkpxKWKkME

[Mike OMelia]

Exactly. What the heck is going on? Btw, I did run a same height piece of pine through, no problem

[Mike OMelia]

Coco is very oily. I don't think of blood wood as oily. It sure does produce a lot of dust. And, I still have no idea what that issue is.

[Bruce Page]

If you go to YouTube and read the comments he says it was because there wasn't enough tension on the blade.

[Mike OMelia]

Can't see the comments! What is up with that?

[Bruce Page]

Can't see the comments! What is up with that?

:confused: Clicking on the YouTube icon, lower right of the video above will take you to the video on YouTube. Comment section's below video.


Here's what he said:

ShabbyChicguitars
3 weeks ago

Just to update... the cause of this might seem counter-intuitive, but it's actually because there's not enough tension on the blade. These carbide-tipped blades require a lot of tension, and this saw was simply hitting its limit with extremely hard, very thick hardwoods. I've since moved on to a more robust resaw and when I feel this problem coming on I make sure the piece is well supported, crank up the tension, and all is well. I've put literally thousands of feet of 9-14" thick really dense woods like cocobolo, Honduran rosewood, African blackwood, all kinds of ebonies, super hard bubinga... - you name it - through a lot of these carbide blades and can now feel this problem coming on and can act accordingly.

One other thing is to make sure the blade is moving as fast as it can... this is a variable speed saw and I believe when I made this video it was set to a slower than max blade speed... it still hit a wall with super hard and thick woods but a faster speed bought me a little extra performance.

My advice: if it starts to grab, make sure the saw is set up to max blade speed, the piece is flat on the bottom and well supported by the table, and that tension is as high as the saw will go while still tracking properly on the wheels. Go slow, and if this happens again either pick a softer wood for your project or think about getting a bigger, beefier machine.

Happy resawing!

[James Nugnes]

Boy I don't like running power tools right at their max limits. I guess ya' gotta' do what ya' gotta' do. I know it is easy to say it and harder to do it, but I believe in getting as close to twice the tool I need for the worst job I expect to have to do. These Carbide Tipped blades seem to be just the sort of thing that puts one right at the limits of the tool on a regular basis.

[Mike OMelia]

Thanks for the replies.

What do u mean that carbide tipped blades put machines at their limits?

[James Nugnes]

A carbide tipped blade of a particular size requires more tension to function properly than the same blade in a carbon steel. Depending on the size of the blade you might even tension it so much that you start to move the pillar and the frame of the saw. Very few long relatively thin pillars will stand up to the amount of pressure you can exert via two wheels, a band of steel and a tension adjustment wheel against the pillars long axis. The saw wheels, the band and tension adjustment wheel are going to win that battle every time. IMO while triple wall and pyramid shapes are all designed to stave off the effects of the amount of pressure you can exert against that long axis, at some point the wheels, the band and the tension adjustment are going to win out unless the thing has a horribly under-engineered spring and the thing pops right out of the housing as you tension. Never seen that happen but give my cautiousness, its not likely anyway. So for example since I tend not to like to get near the limits of a tool's speced tolerance if the biggest blade the manufacturer claimed could be used on my saw was 0.75" I would very likely not even attempt to use a 0.75" carbide tipped blade on that tool. At most I might put a 0.50" carbide tipped blade on it. If I thought I needed the services of a 0.75" carbide tipped, I would buy a saw that had a 1.00" maximum blade upper limit and then use carbide tipped blades no greater than 0.75" on that saw and i would likely even be cautious about that.

Advertised specs are the competitive battlefield for companies trying to secure our business and the playground of every company's Marketing Department with only a passing nod in the direction of the Engineering Department. I have no intention of putting my safety in their hands and fooling around at the tool's advertised spec limits does exactly that. Just not worth it to me.

[Mike Cutler]

James

I'm going to respectfully disagree that a carbide tipped blade requires any more, or less pressure, in the form of tension to run properly. The carbide tip is simply for longevity and quality of cut over the life of the blade. The blade itself is still steel, and within the realm of tolerance, Young's Modulus of 2.9 E+07 is applicable to any blade out there.
The pressure, in psi, to achieve proper tension is the same for any blade, regardless of size or manufacturer. What changes is the total amount of force applied to a band saw frame for a given band size and cross sectional dimension.
The saw in that video is well capable of cutting the material in that video, but the operator is approaching the limits certainly. Not only because of resaw height, but motor power too. It's a nice saw, but it has a small motor, and I suspect that in addition to blade tension, his saw also has some pitch buildup on the surface of the bandsaw wheels due to insufficient dust collection.
I have this same saw, and have resawn many feet of dense tropical hardwoods with it, and have had it do something similar to the response in the video. I use a 1",Lennox, 2/3 varipitch, Tri-Master blade. I also know it's shortcomings with respects to dust collection.

[Phil Thien]

I've experienced thuds when resawing that traced back to a slipping drive belt. Only happened on very hard/tall stock.

[Mike OMelia]

I'm actually talking to the guy in the video on another forum. One common theme is that blood wood is one of the more difficult woods to cut. Another is tension. I think that blood wood may have dulled my blade. There is a gray cast around each tooth. This will scrape off. Someone else said blood wood contains silicates. Still looking at this.

[Mike OMelia]

Never mind the silicate comment. Not true

[Mike OMelia]

I must admit that I am surprised that no one has come forward with a clear, perhaps physics based explanation of this problem. I have heard tons on the difficulty of cutting bloodwood, so that is a given. But what about blood wood makes it such an exceptional problem? Yup. I get it. The cut binds the blade and blam! But why ?

[Steve Rozmiarek]

I'll make a guess at what's going on. Ever got a handsaw stuck in a kerf? It happens because the dust doesn't clear out quickly enough, and the blade jams. More set fixes it. Carbide blades don't have much set so they can make a smoother cut. On a dense wood, the potential problem is greater. All species cut differently, different size, shape and density of the swarf. There is no one size fits all blade. I'd personally recommend using a blade with more set. It'll make a rougher cut, but it will fix the problem.

The recommendation to run faster blade speeds will help the issue of course as the blade is clearing the cut more times per second. There is a limit to speeds effectiveness though.

I really don't think its usually a tension problem. Tension keeps the blade from fluttering, and to a certain degree, resists wandering. A sharp, wide kerf blade with very few teeth per inch will require less tension. It will never do a very good job of a smooth cut though. Carbide will do a clean cut, but at the tradeoff of less margin for error in tension, blade speed, swarf clearing, etc. No free lunch.

Just my opinion based on my experiences.

[Phil Thien]

Your drive belt is slipping. You need more tension on the belt, not the blade.

What is happening is the larger board is causing greater drag on the blade, which is causing the drive belt to slip just a little tiny bit. Once the belt grabs again, the blade is grabbing the stock and causing you to brown your shorts.

Just add more tension to the drive belt.

I've experienced this EXACT SAME PROBLEM. Exactly. So my confidence level is very high that I'm correct on this.

[Steve Rozmiarek]

Your drive belt is slipping. You need more tension on the belt, not the blade.

What is happening is the larger board is causing greater drag on the blade, which is causing the drive belt to slip just a little tiny bit. Once the belt grabs again, the blade is grabbing the stock and causing you to brown your shorts.

Just add more tension to the drive belt.

I've experienced this EXACT SAME PROBLEM. Exactly. So my confidence level is very high that I'm correct on this.

Yep, Phil's right as to the ultimate cause of the dramatic end "explosion". A slipping belt is the first "relief valve" if the blade jams. A broken blade is probably second. Assuming your drive belt is tight though though, see my previous post.

[Mike OMelia]

All right. I will check the dive belt. I have tightened it before, but it could have loosened up again. I'm also gonna clean the wheels (using Simply Green). I am also going to do a cut before and after. And video it. Thanks!

Mike

[ian maybury]

It's an odd one, but it's hard to see how a bang like that can be caused by anything other than the blade grabbing in the wood, the motor as a result increasing the blade tension enough to load up and deflect a somewhat flexible section of the chassis - which then lets go with a bang. The upwards bounce of the table in the video tends to support this possibility. This is especially likely to happen with a deep cut (more teeth engaged at once = proportionally more force), also with a relatively wide tooth as on a carbide blade. I'm guessing there may be something about these very strong and oily tropical woods that causes the blade to snatch/bite suddenly (especially if it's not as sharp as it could be), and/or for the oiliness to make it much harder for the blade to clear sawdust which then jams in the kerf.

Phil's belt explanation is likely the difference between it happening and not happening in some cases - if the belt slips when the blade bites but then grips again it certainly seems like it could trigger the effect. The possibility is that the combination of the wood type, blade and depth of cut is just more than the saw chassis can properly handle - that when the blade bites the chassis needs to 'wind up' a bit to get the cut re-started, at which point it suddenly releases. An initial thought was that somehow the increased tension in the blade when it grabs might be causing the tension spring to compress, only to release with a bang when the blade breaks free again - but it i can't see how this could be happening. The geometry doesn't seem to add up. (??)

Mathias at Woodgears makes a very nice explanation of how the tooth form and depth of cut influence cutting forces in this video - along the way he pretty very graphically demonstrates why deep resawing (which needs proportionally more feed force) requires a wider blade and/or higher tension - and why ultimately getting the job done comfortably requires a strong/heavy saw rather than one running close to its structural limits: https://www.youtube.com/watch?v=fK9m5PadmiI

[Mark Bolton]

Ive been reading this thread and resisted chiming in because other than from a sawmill standpoint I am not a resawing/bandsaw efficiando but when I read and watched this initially my first thought was the blade geometry. This kind of thing is kind of common when sawing on the mill if your someone who simply saws with blades ground to a single profile. I have had this exact experience on the mill with woods like Hackberry and its where the hook angle on the blade is simply too aggressive for the material being sawn. The same thing happens a lot of times even with a chainsaw when cutting maple. It almost feels like your catching nails in the cut but its just because the saw's teeth are catching in the wood fibers.

Im sure the drive belt is acting as a bit of a clutch and also a spring in that when the blade catches, the belt loads up, and then releases. The combined stored energy of the saw frame, blade, belt, all combine to release in a violent manner.

I have had this happen on the mill so sharply that it will actually jump the saw head off the rails.

For me at least, it always happens when I am trying to saw something I know I should swap blades for and dont. If dont have any blades with me ground to a shallower hook and just try to get through the next few logs on the skidway, Im in for some rockin and rollin. If I step down to a shallow hook the problem disapears.

Again, no concrete info with regards to the OP's issue but it is a very very familiar thing.

[Mark Bolton]

Your drive belt is slipping. You need more tension on the belt, not the blade.

What is happening is the larger board is causing greater drag on the blade, which is causing the drive belt to slip just a little tiny bit. Once the belt grabs again, the blade is grabbing the stock and causing you to brown your shorts.

Just add more tension to the drive belt.

I've experienced this EXACT SAME PROBLEM. Exactly. So my confidence level is very high that I'm correct on this.

I would agree completely that more drive (and of course more saw) would allow one to overcome the catch. But I will be that a different tooth geometry would solve the problem as well. I replied with regards to a bandmill and there is no option for me to increase drive tension or saw/frame size.. Tooth geometry is the solution for me and luckily I grind my own blades so I can have a few shallow hook blades on hand.

If the OP is sawing other materials with no problem its more than likely a blade/tooth geometry issue as opposed to the drive belt tension though overpowering the problem can surely beat it into submission ;-)

[ian maybury]

That's a fair comment Mark - in that the Woodmaster CT is a pretty aggressively hooked/raked blade so far as I know. If the rake is enough that it's drawing the blade into the cut at a faster rate than the saw has the power or stiffness to handle (in tough wood and in a deep cut) then it seems quite likely that less rake would improve the situation. A less than sharp blade ccould compound the situation - it can take a lot of feed force to get them to bite to start cutting, but once the rake/hook gets in the mix it could quickly self feed the blade in a similar manner. Only to potentially cause an even worse issue because the blunt teeth require more force to get them to cut…...

[Mark Bolton]

That's a fair comment Mark - in that the Woodmaster CT is a pretty aggressively hooked/raked blade so far as I know. If the rake is enough that it's drawing the blade into the cut at a faster rate than the saw has the power or stiffness to handle (in tough wood and in a deep cut) then it seems quite likely that less rake would improve the situation. A less than sharp blade ccould compound the situation - it can take a lot of feed force to get them to bite to start cutting, but once the rake/hook gets in the mix it could quickly self feed the blade in a similar manner. Only to potentially cause an even worse issue because the blunt teeth require more force to get them to cut…...

As I said, Im not in any way an authority on the issue. Im not sure that I have ever reduced my hook angle to a point where I had a hard time getting the blade to start cutting. The result is usually just a slow cut if the angle is too shallow for the material being sawn. Again, Im talking about a band mill where "self feeding" would be a dream but it never occurs.

I would imagine if you are resawing dry wood and you are at the point of self feeding you must likely be teetering on the precipice of catastrophe but thats just an assumption :eek:. I for one would not be interested in having my work or my tool doing anything by its "self" if you get my drift (pun intended).

I can only guess a degree or so one way or the other (or perhaps even less) would make a substantial difference without resulting in substantially harder feed pressure. That said, I would guess as opposed to keeping different blades on hand opting for another work around would be desirable.

Again, Im likely totally wrong on this but seeing the saw's reaction felt completely at home to me with regards to blade geometry. I would personally wonder how many times a consumer grade saw can withstand that level of shock without something giving way.

[Mike OMelia]

While I find Mathias interesting and informative, I worry that his wooden bandsaw is a poor model for the problem. I wouldn't try this stuff on a saw like that. I might've in the market for a beefier saw

Mike

[ian maybury]

I'm guessing that Mathias is a chap that ploughs a very independent furrow - guided by priorities that may not be everybodys. For sure wood seems unlikely to take over as a professional quality bandsaw construction material, but its perhaps all the more reason for his being conscious of cutting forces. He's very bright, and in that case i thought did a nice job of demonstrating his point about cutting forces….

[Mike OMelia]

I agree with that.

[Mark Bolton]

Your drive belt is slipping. You need more tension on the belt, not the blade.

What is happening is the larger board is causing greater drag on the blade, which is causing the drive belt to slip just a little tiny bit. Once the belt grabs again, the blade is grabbing the stock and causing you to brown your shorts.

Just add more tension to the drive belt.

I've experienced this EXACT SAME PROBLEM. Exactly. So my confidence level is very high that I'm correct on this.

Phil,
This has got me wondering if perhaps this is also what happens on the mill and the hook angle is just a remedy. Is your feeling that when the drive belt slips, the blade stalls or slows, and catches in the wood? Or is it that the shock is coming from the drive belt itself? Both?

Cant tell in the video if the blade stalls, I know it doesnt on the mill but it happens so fast it would be hard to tell anything anyway.

I dont doubt that it has to be something non-blade related in the case of resawing because it doesnt seem the blades are even available in different hooks. I dont do a lot of resawing in the shop and if I do I just do it on the mill.

Very interesting and got me thinking. There is a clutch on the mill so the slipping thing is complicated by that but makes total sense.

[Erik Loza]

Late to this discussion but I have as much experience as anyone with a 1.0" Woodmaster CT. First, I agree that the stalling out during the cut is lack of proper tension. The blade hits various voids or changes in grain in the wood and takes a dive because the tensile strength just isn't there.

Mike, what if you tried a 0.50" carbide? Or a Die Master for that matter? I have my doubts that your machine is capable of properly tensioning that 1.0" carbide.

Erik Loza
Minimax

[Phil Thien]

Phil,
This has got me wondering if perhaps this is also what happens on the mill and the hook angle is just a remedy. Is your feeling that when the drive belt slips, the blade stalls or slows, and catches in the wood? Or is it that the shock is coming from the drive belt itself? Both?

Cant tell in the video if the blade stalls, I know it doesnt on the mill but it happens so fast it would be hard to tell anything anyway.

I dont doubt that it has to be something non-blade related in the case of resawing because it doesnt seem the blades are even available in different hooks. I dont do a lot of resawing in the shop and if I do I just do it on the mill.

Very interesting and got me thinking. There is a clutch on the mill so the slipping thing is complicated by that but makes total sense.

I highlighted in bold what was occurring for me. The thing is, the belt slip happens in a fraction of a second, I don't think you'd actually SEE the blade slow/stop even if you were watching it.

It is pretty violent when it happens, the saw really bucks. It sounds wrong-enough that my wife called down the stairs after it happened asking if I was okay.

While the bucking never broke a blade, the first time it happened I thought that is exactly what happened. I was very surprised to find the blade in tact. Though, I've broken blades before and I'd say the buck from a slipping belt is 3x to 4x more "exciting" than breaking a blade.

There is no doubt in my mind through that if I hadn't found the source of the problem, that I would have broken a blade or something more serious. The bucking is really something.

After thinking about the problem I decided it had to be the belt. I snugged things up and then pushed some 6" high hard maple into the blade very quickly and was unable to duplicate the bucking. That was a year+ ago, and I've used the saw a bunch since then w/o experiencing the problem.

[Mark Bolton]

The bucking is really something.

Yeah, the video alone looks catastrophic. Nothing like a blade breaking. The "browning of shorts" statement would seem spot on haha.

[Phil Thien]

Yeah, the video alone looks catastrophic. Nothing like a blade breaking. The "browning of shorts" statement would seem spot on haha.

About ten years ago I had a desktop PC in my basement shop and one of my kids set up some sort of chat software on it. When one of her friends would log into the same software, the software would announce "ACTIVATE" through the sound card/speakers.

Fast forward about two months later and I had been testing some speakers I built by hooking a Carver 200-wpc amp to the output of the sound card. I was playing some test tones through the PC, and also listening via the PC's CD player.

So I stopped for a while I was working on something else and never turned off, or turned the gain down, on the Carver amp.

And then her friend decided to log into the chat software.

So I hear this "ACTIVATE" at nine million decibels.

And I swear I nearly activated my bowels.