The Forestry Forum

Curious about dial indicator type blade tension gauges that clamp to the blade.
The dial indicators seem to read directly to psi tension.  Do they come with a chart for proper setting for different widths & thicknesses of blades?
Would seem that the width would need to measured from the back to the bottom of the gullet.  Since you're measuring stretch, blade cross section would be important.  An 1¼" blade is going to stretch a lot more than a 2" under the same tension.

I have the Lenox Tension Meter.  Reads in thousand psi.  No tension guide needed.  You call the blade manufacture (or sawmill manufacture) and ask what psi they recommend for their bands.  Most will be in the range of 20,000 to 30,000 psi.  Don't matter if the band is 1-1/4" or 2" the psi will be the same.

Don't get too hung up on band tension.  My TK won't come close to tensioning a 1-1/2" .050 or thicker band to the manufactures specs.  The spring is too light.  The bands saw fine and I get a long life before breaking one.  I believe this is because I'm on the light side of the recommended tension.

Quote from: D6c on September 28, 2021, 08:45:51 PM
Curious about dial indicator type blade tension gauges that clamp to the blade.
The dial indicators seem to read directly to psi tension.  Do they come with a chart for proper setting for different widths & thicknesses of blades?
Would seem that the width would need to measured from the back to the bottom of the gullet.  Since you're measuring stretch, blade cross section would be important.  An 1¼" blade is going to stretch a lot more than a 2" under the same tension.

The goal in tensioning the blade is to reach a certain stress level (tensioning force per unit of blade cross section area) not a uniform tensioning force regardless of blade cross section.  The actual tensioning force will be different for different blade cross sections, thicker and/or wider blades require a higher tensioning force to achieve the same stress level.   The gage reads tensile stress directly since it is actually measuring strain (the amount of stretch) which is directly proportional to the stress level.   No chart or correction is required for different blade dimensions.

Quote from: bobnic on September 28, 2021, 09:17:33 PM

Quote from: D6c on September 28, 2021, 08:45:51 PM
Curious about dial indicator type blade tension gauges that clamp to the blade.
The dial indicators seem to read directly to psi tension.  Do they come with a chart for proper setting for different widths & thicknesses of blades?
Would seem that the width would need to measured from the back to the bottom of the gullet.  Since you're measuring stretch, blade cross section would be important.  An 1¼" blade is going to stretch a lot more than a 2" under the same tension.

The goal in tensioning the blade is to reach a certain stress level (tensioning force per unit of blade cross section area) not a uniform tensioning force regardless of blade cross section.  The actual tensioning force will be different for different blade cross sections, thicker and/or wider blades require a higher tensioning force to achieve the same stress level.   The gage reads tensile stress directly since it is actually measuring strain (the amount of stretch) which is directly proportional to the stress level.   No chart or correction is required for different blade dimensions.

That makes sense.   Same amount of stretch = same amount of tension regardless of size.

 I also have the Lenox meter and run my cooks blades about 17000. That's what they recommended. Works well for me. I'm a firm believer in what works for you is what you should do!!  It's different for everyone!!

 Don't get too hung up on high blade tension, I tried cranking my tension up a few times when not cutting straight and it didn't help at all.  It's more about set, hook angle and a sharp blade. Steve