properly tensioning a bandmill blade

[jimmyjames]

I'm looking for some information on how much tension should be put on a band mill blade, I know a lot of band mills have the hydraulic pressure gauge for they're tensioners but that's not the info I need since the pressure on the gauge isn't the pressure the blade is actually being tensioned too. My band mill I'm sure is more than capable of tensioning the blade to breakage with very little flex in the saw head so I can put a lot of tension on it I just do not know what's the proper pressure. My tensioner is built with a screw thread and will have a spring between the saw head and the tensioner screw, I want to find a spring that has XXX amount of spring pressure at a certain compressed height, that way when I tension the blade I can just turn the handle until the spring is compressed to that certain height giving me the correct tension on the blade, at my work we have a massive selection of high dollar springs in all different diameters, heights and pressures.

 

[Cross Sawmill]

I'm looking for some information on how much tension should be put on a band mill blade, I know a lot of band mills have the hydraulic pressure gauge for they're tensioners but that's not the info I need since the pressure on the gauge isn't the pressure the blade is actually being tensioned too. My band mill I'm sure is more than capable of tensioning the blade to breakage with very little flex in the saw head so I can put a lot of tension on it I just do not know what's the proper pressure. My tensioner is built with a screw thread and will have a spring between the saw head and the tensioner screw, I want to find a spring that has XXX amount of spring pressure at a certain compressed height, that way when I tension the blade I can just turn the handle until the spring is compressed to that certain height giving me the correct tension on the blade, at my work we have a massive selection of high dollar springs in all different diameters, heights and pressures.

Strain, The Correct Term is Strain. The "Standard " number is 25,000 lbs .Some people use More ,Some Less. I run around 50,000 lbs (not a misprint). Good Luck. That number is based on a "Cross-Section" of 1" Square Stock. You will have to "Do The Math".

 

[jimmyjames]

I think I will be running an 1 1/4x .042" blade, with that blade size the calculation comes out to about 1,300 pounds of strain on the wheel pulling on the blade. I'm not 100% sure on my blade size selection,iI have 18 3/4" diameter v belt pulleys for my wheels with 1 7/16" shafts and the wheels have the poly band wheel tires. I do know the thicker the blade the higher strain I can put in the blade and will result in a straighter cut, but my wheel diameter will only allow to go so thick and I do not know what that number is, woodmizer said .042 may be pushing it on 18 3/4" wheels and another company said I could go thicker........ but then again they were just sales people reading off of a piece of paper..... any advice on blade thickness? Also I'm not sure if I should run 1 1/4 or step up to 1 1/2 considering my band wheels are somewhat narrow but then again all of the mills they sell use the same wheels I have....

 

[Kevin]

:eat:

 

[jimmyjames]

Also I'd love to see your blade guides as well, I have some heavy duty can followers that I was going to use for mine, the top would be a cam follower bearing and then the bottom would be aluma-bronze guide for the bottom of the blade and then a hardened race cam follower for the back of the blade, I have an assortment of cam followers from 3/4" diameter and 3/4" wide up to 3" diameter and 2" wide, I regularly get these from work when we do scheduled preventative maintenance on machines and these parts get changed out regardless if they are worn out or still look brand new. I do know the 3" ones are well over $1200 each because I've had to order them before, I'm lucky I get to bring home beer flats of crap like that for $.12 a pound......

 

[Cross Sawmill]

I think I will be running an 1 1/4x .042" blade, with that blade size the calculation comes out to about 1,300 pounds of strain on the wheel pulling on the blade. I'm not 100% sure on my blade size selection,iI have 18 3/4" diameter v belt pulleys for my wheels with 1 7/16" shafts and the wheels have the poly band wheel tires. I do know the thicker the blade the higher strain I can put in the blade and will result in a straighter cut, but my wheel diameter will only allow to go so thick and I do not know what that number is, woodmizer said .042 may be pushing it on 18 3/4" wheels and another company said I could go thicker........ but then again they were just sales people reading off of a piece of paper..... any advice on blade thickness? Also I'm not sure if I should run 1 1/4 or step up to 1 1/2 considering my band wheels are somewhat narrow but then again all of the mills they sell use the same wheels I have....

Jimmyjames,
Your actual number is more like 1,000 lbs. You only go to the bottom of the gullet for width ,so 1" rather than 1-1/4". Also Strain is set on the "Center-Line" of Your Axles. Axle Pull (Center Line) should Equal Twice Band "Direct Pull". Strand on TOP and BOTTOM.
aka SuperAX

 

[Cross Sawmill]

I'm looking for some information on how much tension should be put on a band mill blade, I know a lot of band mills have the hydraulic pressure gauge for they're tensioners but that's not the info I need since the pressure on the gauge isn't the pressure the blade is actually being tensioned too. My band mill I'm sure is more than capable of tensioning the blade to breakage with very little flex in the saw head so I can put a lot of tension on it I just do not know what's the proper pressure. My tensioner is built with a screw thread and will have a spring between the saw head and the tensioner screw, I want to find a spring that has XXX amount of spring pressure at a certain compressed height, that way when I tension the blade I can just turn the handle until the spring is compressed to that certain height giving me the correct tension on the blade, at my work we have a massive selection of high dollar springs in all different diameters, heights and pressures.

Strain, The Correct Term is Strain. The "Standard " number is 25,000 lbs .Some people use More ,Some Less. I run around 50,000 lbs (not a misprint). Good Luck. That number is based on a "Cross-Section" of 1" Square Stock. You will have to "Do The Math".

"Tension" is the "Old Time" Sawmill Terminology for the "Shape" an "Operating" Saw assumes. I have heard some "Experts" say that Thin-Kerf Narrow-Band Saw Blades are not affected by Tension (Operating Dynamics). I believe(KNOW) that they are. So to discuss it , We either have to use existing Terminology or Invent and Define new Terminology.
Steve

 

[jimmyjames]

I think I will be running an 1 1/4x .042" blade, with that blade size the calculation comes out to about 1,300 pounds of strain on the wheel pulling on the blade. I'm not 100% sure on my blade size selection,iI have 18 3/4" diameter v belt pulleys for my wheels with 1 7/16" shafts and the wheels have the poly band wheel tires. I do know the thicker the blade the higher strain I can put in the blade and will result in a straighter cut, but my wheel diameter will only allow to go so thick and I do not know what that number is, woodmizer said .042 may be pushing it on 18 3/4" wheels and another company said I could go thicker........ but then again they were just sales people reading off of a piece of paper..... any advice on blade thickness? Also I'm not sure if I should run 1 1/4 or step up to 1 1/2 considering my band wheels are somewhat narrow but then again all of the mills they sell use the same wheels I have....

Jimmyjames,
Your actual number is more like 1,000 lbs. You only go to the bottom of the gullet for width ,so 1" rather than 1-1/4". Also Strain is set on the "Center-Line" of Your Axles. Axle Pull (Center Line) should Equal Twice Band "Direct Pull". Strand on TOP and BOTTOM.
aka SuperAX

Thanks so the pressure is figured at the narrowest cross section of the blade, got it

 

[Cross Sawmill]

I think I will be running an 1 1/4x .042" blade, with that blade size the calculation comes out to about 1,300 pounds of strain on the wheel pulling on the blade. I'm not 100% sure on my blade size selection,iI have 18 3/4" diameter v belt pulleys for my wheels with 1 7/16" shafts and the wheels have the poly band wheel tires. I do know the thicker the blade the higher strain I can put in the blade and will result in a straighter cut, but my wheel diameter will only allow to go so thick and I do not know what that number is, woodmizer said .042 may be pushing it on 18 3/4" wheels and another company said I could go thicker........ but then again they were just sales people reading off of a piece of paper..... any advice on blade thickness? Also I'm not sure if I should run 1 1/4 or step up to 1 1/2 considering my band wheels are somewhat narrow but then again all of the mills they sell use the same wheels I have....

Jimmyjames,
Your actual number is more like 1,000 lbs. You only go to the bottom of the gullet for width ,so 1" rather than 1-1/4". Also Strain is set on the "Center-Line" of Your Axles. Axle Pull (Center Line) should Equal Twice Band "Direct Pull". Strand on TOP and BOTTOM.
aka SuperAX

It takes more "Direct-Pull" to Strain a Bigger blade; ie .042 by 1-1/4 equals 1,000 lbs "Direct-Pull" for 25,000psi. .050 by 1-1/2 equals 1,500 lbs "Direct-Pull" for 25,000 psi. (approximate numbers) Bigger,Thicker Blades DO Have Issues with "Flex-Life" on Small Wheels. ALWAYS Use the Smallest Blade that will "Do The Job". If One Needs the "Beam Strength" of a Bigger Blade either Run It and not Worry about them Breaking or Get Bigger Wheels and Run It and not Worry About Them Breaking.

 

[Cross Sawmill]

I'm looking for some information on how much tension should be put on a band mill blade, I know a lot of band mills have the hydraulic pressure gauge for they're tensioners but that's not the info I need since the pressure on the gauge isn't the pressure the blade is actually being tensioned too. My band mill I'm sure is more than capable of tensioning the blade to breakage with very little flex in the saw head so I can put a lot of tension on it I just do not know what's the proper pressure. My tensioner is built with a screw thread and will have a spring between the saw head and the tensioner screw, I want to find a spring that has XXX amount of spring pressure at a certain compressed height, that way when I tension the blade I can just turn the handle until the spring is compressed to that certain height giving me the correct tension on the blade, at my work we have a massive selection of high dollar springs in all different diameters, heights and pressures.

Strain, The Correct Term is Strain. The "Standard " number is 25,000 lbs .Some people use More ,Some Less. I run around 50,000 lbs (not a misprint). Good Luck. That number is based on a "Cross-Section" of 1" Square Stock. You will have to "Do The Math".

"Tension" is the "Old Time" Sawmill Terminology for the "Shape" an "Operating" Saw assumes. I have heard some "Experts" say that Thin-Kerf Narrow-Band Saw Blades are not affected by Tension (Operating Dynamics). I believe(KNOW) that they are. So to discuss it , We either have to use existing Terminology or Invent and Define new Terminology.
Steve

Sorry, I was not Clear on Stating the Strain Numbers. They are in P.S.I. Based on Cross-Section of 1 '' Bar Stock. Getting a "Handle" on these numbers takes a little Practice. PSI and "Direct Pull" Numbers are only the Same if Your Blade has exactly a 1'' Cross-Section.