band jumping out at end of cut?

[New Brunswick]

  Band seems to be jumping out at the end of the cut is this normal? Maybe not enough tension?  It does it with a new or old blade at times, any ideas of what I may be wrong?

[Dan_Shade]

when you say "jumping out", do you mean it's popping up, or down when you exit the cant?

[Dave Shepard]

I now that on the 24 HP Mizer I used to run the whole head would give a bit of a shake when it came out of the cut. Usually when I was pushing pretty hard and had a band that was about ready to be taken off.


Dave

[woodmills1]

my question would also be out or up?


out, I dont see, but would think something is really wrong and your guide wheels are pushing the blade


up I see when I am pushing a blade that is dull or it has hit nails, so I don't waste another on the next nail or dirt.

[New Brunswick]

  I mean it seems to be dragging through the log and at exit the band will jump ahead on the blade guides 3/16  or maybe even 1/4 of an inch. It will do it with a new blade right out of the box, I just switched to a different type of band, I was using simmonds red streak, and now I am trying wm bands. I cut about 1000 bdf on the first wm band before it broke, I sharpened it 4 times, was kinda hopin for a bit longer life, but it is probably more operator fault than band. I recently changed belts on band wheels and had to go with a slightly longer belt, I wonder if it is traveling on the belt maybe a little or saw dust getting under v belt.

[Dan_Shade]

do your blade guides have back supports?

[woodbowl]

do your blade guides have back supports?

Dan is on the right track. A band that jumps forward when exiting the cut is a signature of too much gap between the back of the band and the blade guide rollers. I'm not familar with C.B.M. mills, but according to your first post with pics it looks simular enough to use the guidelines that other bandmills use. Woodmizer has the system down very good. You need to set a static gap of 1/16" on the power side and 1/8" on the idle side. This allows the band to flex untill it reaches the back lip of the blade guide roller. Exceeding this measurement will result in what your talking about. What you don't want is the band touching the back of the roller. This results in premarure blade breakage and worn blade guide rollers.

On your first post there is a picture of the blade guide roller on your mill. It looks as though it may be coned shaped. If so, it has worn away in the front and you could use some new rollers as well.

[woodmills1]

1000 foot 4 sharpens?

doesn't sound right

my last three boxes of mizer blades have lotsa life still left.

[New Brunswick]

  My guides do have do have backs on them, and yes they are coned shaped,(keen eye woodbowl) It is a poor set up right now on my mill for tensioning the blade and the guide rollers. I have looked at a wm down the road from me and really liked the way the guides adjusted back and forth, on mine I loosen a bolt and push or pull it, which in turn will change the hieght of my blade, the arms do not travel level across. I need a retro fit with somthing different, but I do not know enough yet to know exactly what I want.(besides a new wm) When I bought the wm blades I also ordered 2 new rollers but the shaft on mine will need turned down a bit to accept the wm rollers.

     Woodbowl you said to set a gap, which I do, but if I set it at 1/16 it would be hard against the back of the roller all the way through the log, I have tried 1/4 and even then it wants to travel back. I find 3/8 works most of the time, but for some reason it seems to be dragging more so than last year, I don't saw alot, or know much about sawing.

[logwalker]

Woodbowl is correct. It should be against the roller flange when in the cut. If you are setting 3/8" ahead then you are not supporting the blade and it will crack and break from the back and jump forward when exiting the cut.

[woodbowl]

What you don't want is the band touching the back of the roller.

That's only when the blade is not in the log.

but if I set it at 1/16 it would be hard against the back of the roller all the way through the log

That's what it's supposed to do, it's a back stop. The rollers are hardened so they last a good while. When you get this adjustment down, your gonna like your new mill.  ;)

[New Brunswick]

  Last year when I bought the mill I was running it with the back of the band touching the back of the guides, this year I visited a fellow down the road with a wm electric, and watched him for a while and he told me that his band never hits the back of the roller guide. He also ran a lot more tension than I did, his was around 2500 lbs. I do not have a gauge as mine is adjusted by a small pipe wrench turning a bolt into a spring. After he tightened his I pressed down on it to kind of get a feel for it, I could not believe how much tension was on the band. Anyways I have been trying that method for a while but seem to be getting less life out of the bands, and when they break it is right under the tooth in the gullet but close to the tooth. Also last year I would get 8 to 12 sharpening per band on good clean logs, but noticed as they hit the back of the roller guide the tip of the guide was running on the set of the teeth so that is when I tried pulling the guides back a bit more. So I better get the new guides on as I think the old ones are wore out, anybody sell the roller guide track that you know of or would that be something you would have to fabricate? Also when I bought the wm blades the rep advised me to go to 45 thou instead of 42 which I had been using, he said they don't last as long but cut alot faster, he told me to change them every 2 hrs and you should get 6 to 10 sharpenings out of them, is this what you fellows are getting.

[mike_van]

Lots of things are 'trade offs' with band blades - A thicker blade may cut faster but won't last as long, pulling a blade & sharpening before its REALLY dull takes time, but it'll last longer too.  More tension than needed to get a straight cut will shorten blade life too. We've all [at some point] cut with a dull chainsaw, and know how hard it is, how much more work it takes - Imagine the bandmill with a dull blade - How hard it's working.

[woodbowl]

NB, there are several issues here that need to be addressed before you can get top performance out of your band.

.... but noticed as they hit the back of the roller guide the tip of the guide was running on the set of the teeth

You need a set of roller guides that match the blade width. Your guides are either for the next size up or the bands are for the next size down. If the band and rollers are matched, then the band has been sharpened away to the point that the teeth can indeed ride on the roller.

For the HP motor that you are running a .045 band will not cut as fast as a .042 .

he told me to change them every 2 hrs and you should get 6 to 10 sharpenings out of them

  Sawing for 2 hours in oak VS sawing 2 hours in white pine is not the same. Changing the blade at the right time is something that is learned. For me, it is the sound of the motor as it labors. Taking it off before it gets dull, dull, dull will maximize the life of the band.

he told me that his band never hits the back of the roller guide. .....  I have been trying that method for a while but seem to be getting less life out of the bands, and when they break it is right under the tooth in the gullet but close to the tooth.  .........

Look at one of his fresh broken blades. The break occures at the back first, due to the excess tension, along the back of the blade as it flexes in the cut. The gullet area is in compression. There will be a shiny, fresh break at the gullet side and a dull look to the back.

On the contrary, rollers that are too forward, as to rub continously on the back of the band will cause the blade to break on the tooth side.

[New Brunswick]

   I think I have the proper guides on, the new ones I received from wm are the same depth as my old ones. But as you noticed woodbowl the old ones are tapered or cone shaped, I am going to get the shaft turned this week to accept the  wm guides. The new bands hit the back stop and are about 3/16 from running on the set, some of my old bands had been through the sharpener several times so maybe they were getting down too narrow.

  So I am running a 20 hp onan and you say a 42 thou blade will cut faster than the 45?  I am only on the 2nd blade from wm and I have found really no difference between them and my old ones to speak of, I guess it would not be fair for me to say too much about the bands until I get the guide issue solved.

  I cut mostly pine and hemlock and black spruce and cedar, no hardwood to speak of, a lot of the pine are big and I find it cuts hard especially around the dead knots, the clear boards seems to zip through those pretty easy, and the live knots where the branches were still living not to bad either, but the dead ones will make the mill moan and the band will want to travel up. Hemlock I find saws really easy, it's the slabs from hemlock that I'm not real fond of. In spruce some of the knots are pretty hard but stills seem seems to saw pretty well and I would have to say easier than pine. Cedar saws great but blade seems to dull fast.

  I must thank you guys for taking the time to help me out, you know after you read other people's advice and experience's it all seems so easy, A great bunch here.

  Thanks again, NB.

[woodbowl]

So I am running a 20 hp onan and you say a 42 thou blade will cut faster than the 45?

I have 25 hp and I can tell it as well. Speed is not the only issue, they're more efficient for low hp mills. You wouldn't think that a few thousanths could make that much difference. Monks are .041 and are forgiving in a lot of ways and have long life, but they need to be maintained close after several sharpenings. They are availible from Menominee, to the left. That's about as thin as I can run. A .035 is just too thin and limber to turn the wick up on.

[gizmodust]

NB, I run both 42 and 45s on my NW.  I have a 15 Koler and it handles both pretty good.  I found that the 45s takes the slabs off better because they're cobalt.  Especially in cedar.  I've heard that the worse thing on a blade is the bark because it holds all kind of the nastys of nature.  I notice more of a jump down when the blades get dull.  I heard the same about the time, and agree with woodbowl.  Experience is the best guide.  When the mill sings its happy song, you'll know.  Even with ear protection, especially with ear protection, you can hear it better.  When the song seems to go to a deeper tune, you'll notice you're pushing harder.  Least that's my impressions.  Good luck.

[New Brunswick]

   The more I think about having my guides set to far back and not letting the band touch the back stop for support, the band maybe is getting pushed  back on the on the v belts a bit as it goes through the log and at exit it centers itself causing it to jump ahead.
  Woodbowl you find the 41 thou bands are more efficient as they go through the log easier, or less money to buy, and what do you mean by forgiving?
  Gizmodust I agree about the bark, wm's have a great set up with the debarker, it really must improve band life.
  Anybody ever see an old wm that has been laid to rest (if that happens), I would be interested.

[woodbowl]

you find the 41 thou bands are more efficient as they go through the log easier, or less money to buy, and what do you mean by forgiving?

Not having the hp, a thin blade has less strain, but there is a point of dimishing returns. I wish I could run .035, but they are just too limber. Woodmizer has a good blade if you don't want to cut your teeth just yet by experimenting.

I don't run Monks very often, because I can't push them like I can with a stiffer blade. I do this for a living so time is money. Stiffer blades break sooner, but make the money in short time. Monks last and last and can be resharpened, but then you have time invested in sharpening and setting. They don't seem to hold an edge as well after a few sharpenings. Great for the novice, not so great for higher production. Trying out different blades is kinda fun if it doesn't dig into your pocket.  ;)