A question on blade tension WM owners

[Jim_Rogers]

Recently, last Friday, I had several conversations with the WM guys at the logging and sawmill equipment show in VT.

We discussed blades a lot and that included blade tension.

I have alway ran my tension in the orange on the gauge:



And now they are telling me to not be afraid to turn it up, so that the blade will be even tighter.

Some of them, other users there, said they turn it up till the needle is about pinned at the high end.

My question is what tension do you run?

I suppose I should say also what blade size or thickness matters, but I'm just curious if you're running "higher" then the orange zone.

When I was sawing that 100 year old live oak, Randy of WM blades told me to turn it up above the orange for my 4° blades.

Thanks in advance for your replies.

Jim Rogers

[Chuck White]

I run 1¼x.045 10° WoodMizer Double Hard blades.

The last couple of years I was running my tension about half way between the top of the orange and the peg.

This year I decided to run on the line between the yellow and the orange.

Either setting has worked well for me, but I'm getting a little longer blade life setting the tension on the yellow/orange.  As much a 3 additional resharps.

I think the higher tension would come into play more when you increase your feed speed!

[OneWithWood]

For all blades I run within the orange.  I do start out at 2500 but then it settles down.  As the day heats up the tension will rise and I bring it back to within the orange.  Very rarely break a blade. 

[Dave Shepard]

.055", 3,000 psi always.

[Jim_Rogers]

Thanks Chuck.

I'm running the 1 1/4" .045's 10 degree WM doublehards most of the time myself.

But you are bringing up another question that I have and I was going to start another thread about it.

And that is feed rate.

But I'll mention it here, now.

I was being trained on my mill back in 94 and I asked how fast to you feed the blade through the log?
Well the trainer was chatting with another WM owner and he said creating a joke: "if you're not making enough money, saw faster."

That answer didn't help me much, and I wanted a truthful answer.
I wanted to understand how much to turn up my feed rate dial so that I would be sawing correctly.

Another employee of WM told me to turn it up until you hear the engine governor kick in and saw at that speed.

Being new to sawing I didn't understand that at all. And I felt that it was an experience judgment and I didn't have any experience.

When I got the mill home, I went to my local auto parts store and asked them for a tachometer for an Onan engine. They said they didn't have one. And that I should go to an Onan engine dealer and see if they had one.

I went to the local Onan engine dealer, and asked them if they had one.
The said they didn't have an "Onan" engine tachometer. But that they could get me a Kholer engine tachometer.

So they got me one. I installed it and have been using it ever since.
To install it you wrap a wire around one spark plug wire and hook another wire to a ground. That's it. And when it isn't reading engine speed, it reads engine hours since installed.

I use this tach to set my "high" idle and my "low" idle engine speeds.

I watch this tach from time to time to see how the engine is running and at what speed it is at while sawing.

Is anyone else running a tachometer on their engine?

Here is what I'm finding.

When I sawing with a resharpened blade, just about any type of wood, oak or white pine, and I get the engine speed to drop more the 50 rpm's the blade seems to make wavy lumber.
If I keep it within 50 rpm's of high idle is cuts fairly smooth and true.

But to cut with 50 rpm of high idle I have to feed fairly slow. Of course it all depends on the type of wood and the width of the cut I'm making, wider is slower of course.

So, again I asked, at the show event, what should my "high" idle speed be set at.

I was told, by the manual when I got the mill, that it should be something like 3250 or 3400 (seems to come to mind). But later on, I was told to run it at 3600 as it would give me a little more horse power. I think the mechanic who adjusted my valves told me that this was high idle on welder machines.

And I was recently told that again at the show. High idle should be 3400.

And that at sawing speed I should be at or it should drop 200 rpms. To 3200.

I can't seem to ever get it to ever drop 200 rpms and cut straight lumber.

I just got back a box of blades from resharp. And I know there are some brand new replacement blades in the box.
I'm going to put a new one on the next time I'm sawing. Reset my idle speed to their recommended "high idle" and try to saw at a drop of 200 rpms.

It will be a good test, but I don't think that I can saw straight lumber at that feed rate.

Jim Rogers

[CalebL]

I run mine at 2900.  The Woodmizer guy tells me more tension is better and not to be afraid to make it sing.  I haven't had any problems yet. 

[Chuck White]

My high idle is set at 3400 and low idle is set at 1800rpm

Jim, I have the same type tach you do.  Got it from Surplus Center.

I don't always watch the tach, but just check it once in a while and I'm usually a little over 3200 when cutting.

I sharpen my own blades, and when I find myself wanting to turn the feed rate up, it's usually because the blade is starting to get dull and I change it out!

I usually go through 3 blades in a full day of sawing.

[T Welsh]

9° Double Hards and I run them right at the mark between yellow and red and have NO issues. I do watch the gauge quite often. Tim

[jim blodgett]

Hey, everyone, not specific to WM mills, but bandsaws in general, is it fair to say the higher the blade tension, the greater the strain on the bushings, bearings, motor/engine, clutch etc?  The greater the strain on the rest of the machine?

If you could get as clean a cut at a lower blade tension, wouldn't it be easier on the machine?

[Chuck White]

That's the way I figured it Jim.  ;)

[Jim_Rogers]

They did tell me that running the blade at a higher tension would put some stress on your B57 belts.

Jim Rogers

[Dan_Shade]

I peg the gauge when sawing.

[prittgers]

Woodmizer blade experts have said that the BEST way to measure blade tension is with the tensionmeter which is calibrated for steel bands.  They are about $300.  And like many of you, I now run it pegged.  It's important to take the tension off when you're done because you won't have the lube circulating around those roller bearings.  And there will be more blade-belt wear.  But it really does help saw better.

[Larry]

Welcome to the forum prittgers.  You will enjoy hanging round here.

Woodmizer blade experts have said that the BEST way to measure blade tension is with the tensionmeter which is calibrated for steel bands.  They are about $300.

But what they didn't tell you is the same measurement can be made with a $10 set of calipers from HF.  Open the calipers to about 5" and clamp to the band.  Tighten the band and it will stretch.  Each .001 is equal to 6,000 psi of strain.  Most bands run in the 25,000 to 30,000 psi range. 

Engineering stuff courtesy of Young's modulus of elasticity.

This is the actual gauge of which you spoke.  I've only used it a few times but it has shown mill gauges can be off...sometimes a lot off.  I used it Saturday to see if my TK could tension a 1 1/2" band  properly.  It couldn't tension up to the optimum band manufactures specs, as they were quite high.



An auction find for me at $7 cause nobody knew what it was...good thing it wasn't re-branded by WM or it would have went for a lot more.

[Brucer]

Assuming everything is properly aligned and the blades are sharp, the key to straight cuts is to make sure the blade doesn't drop below it's intended speed. The governor on the engine will try to keep the speed constant but if you push the saw too fast it will run out of power and the blade will start to slow down. That's  where you start to see wavy cuts.

The safe way is to saw slow enough that your engine doesn't have a chance to slow down. But that brings up another problem. The longer your blade is in the cut, the more passes each tooth will make through the timber. This dulls the blade more quickly.

Thus the recommendation to feed the carriage as fast as you can without bogging the engine down.

The reason hard knots will cause ripples is that the engine is running at design speed as you cut the relatively soft wood; when you hit the knot it slows down the motor and it takes a moment for the governor to get the motor back up to speed.

Diesels are better than gas engines when dealing with variable loads because they have better torque characteristics; electric motors are even better.

Last year I was setting my tension just above the orange zone. This year I'm trying to keep it in the middle of the zone.

[LeeB]

Here is what I'm finding.

When I sawing with a resharpened blade, just about any type of wood, oak or white pine, and I get the engine speed to drop more the 50 rpm's the blade seems to make wavy lumber.
If I keep it within 50 rpm's of high idle is cuts fairly smooth and true.

But to cut with 50 rpm of high idle I have to feed fairly slow. Of course it all depends on the type of wood and the width of the cut I'm making, wider is slower of course.

And I was recently told that again at the show. High idle should be 3400.

And that at sawing speed I should be at or it should drop 200 rpms. To 3200.

I can't seem to ever get it to ever drop 200 rpms and cut straight lumber.

I just got back a box of blades from resharp. And I know there are some brand new replacement blades in the box.
I'm going to put a new one on the next time I'm sawing. Reset my idle speed to their recommended "high idle" and try to saw at a drop of 200 rpms.

It will be a good test, but I don't think that I can saw straight lumber at that feed rate.

Jim Rogers

I have to wonder if possibly your drive belt is slipping. In this situation you wouldn't see much drop in RPM and still have a big drop in blade speed and thereby cut quality would suffer.

[Jim_Rogers]

Here is what I'm finding.

When I sawing with a resharpened blade, just about any type of wood, oak or white pine, and I get the engine speed to drop more the 50 rpm's the blade seems to make wavy lumber.
If I keep it within 50 rpm's of high idle is cuts fairly smooth and true.

But to cut with 50 rpm of high idle I have to feed fairly slow. Of course it all depends on the type of wood and the width of the cut I'm making, wider is slower of course.

And I was recently told that again at the show. High idle should be 3400.

And that at sawing speed I should be at or it should drop 200 rpms. To 3200.

I can't seem to ever get it to ever drop 200 rpms and cut straight lumber.

I just got back a box of blades from resharp. And I know there are some brand new replacement blades in the box.
I'm going to put a new one on the next time I'm sawing. Reset my idle speed to their recommended "high idle" and try to saw at a drop of 200 rpms.

It will be a good test, but I don't think that I can saw straight lumber at that feed rate.

Jim Rogers

I have to wonder if possibly your drive belt is slipping. In this situation you wouldn't see much drop in RPM and still have a big drop in blade speed and thereby cut quality would suffer.

If you don't hear your belt slipping, how can you tell if it is slipping?

Jim Rogers

[LeeB]

Check the belt tension. I could never hear my old belt slipping. When I took it to WM for a service the belt was probably 50% worn. The new belt and keeping it tight made a big differnece in cut quality.

[petefrom bearswamp]

I was having problems sawing Norway spruce a couple of years ago and went to WM in Hannibal.
Dave Scott sent me home with some .055 blades in 10 and 7 degrees telling me to crank the tension way up.
After sawing a while, I heard a bang and the tension dropped.
The b57 was crushed on the idle wheel causing the blade to run on the metal.
I don't saw spruce any more unless someone brings me some ( i am stationary)
As for tension I run most of the time in the low yellow and have no problems.

[GAB]

Gentlemen:
Concerning blades:  I was told that resharpened blades are sharper than new blades because new blades are stamped and resharpened ones are ground.  I personally can't tell the difference, but maybe it makes a difference in use.

Lube:  The lube being used and quantity of lube may make a big difference in performance. i.e. less friction less RPM drop for the same speed or rate of feed.  I use ERA laundry detergent and water or widshield washer fluid.  If ERA does not work for you then use it to do laundry.  It's no lose situation or experiment.  ERA is less expensive than DAWN.  Quantity depends on species being sawed.  A pint to 4 gallons of water is a place to start for pine, then adjust to your situation or parameters.

Engine:  If you have a high torque engine it will operate differently than a high RPM engine.  I believe that high RPM engines bog down quicker than high torque engines given the same parameters (cutting speed, species of wood, blade configuration, tooth spacing, gullet size, etc.).

The gage on the blade tensioner give you the pressure in the tensioner itself and not necessarily the tension in the blade.  Not having the WM drawings and specs to do an analysis as to how they compare I do not suggest thinking that the pressure gage reading is what the blade tension is.  The reason I say that is the tensioner gage does not know if you are using a .042", .045", or .055" blade.  The thinner the blade the higher the pressure for the same tensioner reading.

I would like to see a picture of how one uses a HF vernier as my blades have a .875" tooth spacing and 5" is 5.714 teeth.  The end that partial tooth is hard to locate.

Does someone have a chart for all three different thicknesses and what .001" of stretch over 5" equates to.  If so I would appreciate the info.  Thanks.

I use .045" blades and crank the tensioner needle to 6:00 o'clock and I don't readjust until it goes to 5:00 o'clock.  Just plan on having spare belts available.  Belts are cheap compared to a bad word of mouth reputation.  I also like the owner there as I crown him or her with the title of Quality Manager.  I inform them that if you see something speak up, as the off bearer you will probably see it before me.

Drive belt tension:  This can be a biggie when it come to wavy lumber.

Oh by the way; I also attended the workshop last thursday at the Fair Grounds in Essex Jct., VT.  It was a good day for it (raining in the AM).

[Peter Drouin]

I pin it all the way around :D :D :D I use 1 1/4 55 7s. all I use :D :D

[Larry]

Does someone have a chart for all three different thicknesses and what .001" of stretch over 5" equates to.  If so I would appreciate the info.  Thanks.

Strain is a constant for each material class.  In other words no correction required for band width or thickness.  Of course it will require more load to get higher strain on the thicker bands.  The Lenox gauge pictured earlier will accurately measure strain on anything form a 1/4" band on up, as will calipers.



0 psi strain



24,000 psi strain.  Digital might make it easier to get a reading.

[mikeb1079]

larry that is excellent.  i've been having quality control issues with my home built miil and band tension is something i need to get sorted out.  i will def try the calipers idea.
thank you  ;D

[crcoffeeguy]

Hi,
New guy here.
I have an LT40 SH and I generally am cutting exotic hard woods.
I was cutting alot of purple heart and monkey pod. Step one was to use stellite blades.
They kept breaking all the time running at the bottom of the orange. After talking to my WM guy I
swithed to running at 2500 atthe top of the orange and I haven't broken a blade yet.
Roger