4x6 blade life mystery

[homebrewed]

Asking for a friend. Recently he did a series of blade life tests vs. blade tension on his saw and got a surprise. Actually two surprises. The first: the blade life was lower than expected, maxing out at around 56 hours of continuous run time. The second: the blade life vs. tension had an inverse relationship -- the higher the tension, the longer the life. The maximum tension used for the test was well below the manufacturer's maximum-recommended tension, and this relationship held true for all 4 tests ranging from 25KPSI at the high end to 15KPSI at the low end. They were all bi-metal blades from the same manufacturer, same shipment so probably from the same manufacturing lot. The blades do not break at the weld, they all appear to originate from the gullet. The life vs. tension curve is close to a straight line with a slope of +2.6 hours/KPSI

The tests were performed with the blade guides removed so the blades were not twisted/straightened during the test. He has a tool to measure blade-tension and a load cell to calibrate the tool, so he had known test conditions. Blade tracking was good during the tests.

Has anybody here encountered a similar problem?

 

[RJSakowski]

An interesting study. I assume that since the guides were removed that no actual cutting was done? Was this a vertical band saw or a horizontal band saw? The 45º twist that occurs with a horizontal band saw might add a twist to the observation (pun intended). What was the blade size?

I run my horizontal band tension quite tight and so far have not had an issue with blade breakage.

Edit: I should have reread the title re: the saw type and blade size. I would think that the twist that the blade guides put in would have a significant impact on blade life. Also, a fair assessment would include testing while actually cutting as that is how the blade is used.

 

[markba633csi]

What are you calling the end of life point for the tests? Breakage? So they all break at less than 56 hours? I wonder how much shorter with the guides?

 

[C-Bag]

Also, a fair assessment would include testing while actually cutting as that is how the blade is used.

I totally agree.

Sorry, this is apples and oranges for me. I don’t see how anything useful was done here. Not even setting up the saw like it should be set up with the guides and actually cutting is not what I would call a scientific evaluation. If Fireball Tool was to do a tensioning test I’m sure that would be meaningful.

 

[homebrewed]

What are you calling the end of life point for the tests? Breakage? So they all break at less than 56 hours? I wonder how much shorter with the guides?

Yes, breakage. My acquaintance was experimenting with a different guide design and got a very short lifetime on a nice Starett blade (about 8 hours!) so he started doing some troubleshooting and discovered this unexpected relationship.

 

[homebrewed]

I totally agree.

Sorry, this is apples and oranges for me. I don’t see how anything useful was done here. Not even setting up the saw like it should be set up with the guides and actually cutting is not what I would call a scientific evaluation. If Fireball Tool was to do a tensioning test I’m sure that would be meaningful.

It's called removing variables. There is science there, and is an often-used method to troubleshoot problems.

If there's no twist in the blade and the blade is running properly on the wheels that should be optimal for blade life (and if you don't think so, please elucidate).

 

[markba633csi]

Lots of variables for sure: brand, tooth set, material of blade. Not to mention how they do in actual cutting duty

 

[C-Bag]

Maybe it’s just me, but I’ve never had a bandsaw blade break. I have replaced them when they were dull(see the recent thread on cutting bed frame rails) or when they have lost teeth and became annoying. I have a lot of hours on horizontal and vertical bandsaws. I’ve been in a shop where 50 brain dead bozo’s were using one 4x6 Jet all day, 6days a week and they mangled and stripped teeth but never broke a blade. The biggest problem was blade jumping off because one of the gearbox bearings died causing the blade to not track. After replacing the bearing and filling it with grease, off it went.

I’ve had my HF 4x6, made in Taiwan for 40+yrs. I don’t use it everyday so without a Hobbs meter there is no way I could keep track of how many hours each blade has on it. Most cuts last just a couple of minutes and run the gamut of materials. And my cheap HF blades last upwards of 5-10yrs. So yeah, it’s a mystery.

 

[homebrewed]

Adding an hourmeter is an interesting thought, but I can see why it would be a waste of money on your typical bandsaw. Who'd think they need to track hours on one.

I'll post a follow-up if we figure out what's going on. It might be useful information, maybe not.

 

[markba633csi]

Brain dead Bozos. Good one, I'll have to remember that